ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
ASD/LRFD Manual - American Wood Council
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2005 EDITION<br />
<strong>ASD</strong>/<strong>LRFD</strong><br />
MANUAL<br />
MANUAL FOR ENGINEERED<br />
WOOD CONSTRUCTION<br />
<strong>American</strong><br />
Forest &<br />
Paper<br />
Association<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
May 2013<br />
Codes and Standards Addenda and Amendments Related to Design Value Changes<br />
The <strong>American</strong> Lumber Standard Committee (ALSC) Board of Review has approved changes to design<br />
values for all grades and all sizes of visually-graded Southern Pine and Mixed Southern Pine lumber, 2"- 4"<br />
thick, with a recommended effective date of June 1, 2013. For more information, visit www.spib.org and<br />
www.southernpine.com.<br />
AWC has developed addenda and other updates to use with new construction designed in accordance with<br />
many of its standards and design tools. However, this document has not been updated to include changes<br />
to design values. Designers are urged to download the addendum to the 2012 NDS Supplement, which<br />
contains the new design values, and use them accordingly with this document.<br />
For additional information or questions, visit the AWC website at www.awc.org or email your request to<br />
info@awc.org.<br />
Thank you.<br />
222 Catoctin Circle, SE, Suite 201 ▪ Leesburg, VA 20175 ▪ 202 463-2766 ▪ www.awc.org ▪ info@awc.org
Updates and Errata<br />
While every precaution has been taken to<br />
ensure the accuracy of this document, errors<br />
may have occurred during development.<br />
Updates or Errata are posted to the <strong>American</strong><br />
<strong>Wood</strong> <strong>Council</strong> website at www.awc.org.<br />
Technical inquiries may be addressed to<br />
awcinfo@afandpa.org.<br />
The <strong>American</strong> <strong>Wood</strong> <strong>Council</strong> (AWC) is the wood products division of the <strong>American</strong> Forest & Paper<br />
Association (AF&PA). AF&PA is the national trade association of the forest, paper, and wood products<br />
industry, representing member companies engaged in growing, harvesting, and processing wood and<br />
wood fiber, manufacturing pulp, paper, and paperboard products from both virgin and recycled fiber,<br />
and producing engineered and traditional wood products. For more information see www.afandpa.org.
2005 EDITION<br />
<strong>ASD</strong>/<strong>LRFD</strong><br />
MANUAL<br />
FOR ENGINEERED<br />
WOOD CONSTRUCTION<br />
Copyright © 2006<br />
<strong>American</strong> Forest & Paper Association, Inc.
ii<br />
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction 2005 Edition<br />
Web Version: September 2008<br />
ISBN 0-9625985-7-7 (Volume 3)<br />
ISBN 0-9625985-8-5 (4 Volume Set)<br />
Copyright © 2006 by <strong>American</strong> Forest & Paper Association, Inc.<br />
All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any<br />
means, including, without limitation, electronic, optical, or mechanical means (by way of example and not limitation,<br />
photocopying, or recording by or in an information storage retrieval system) without express written permission of the<br />
<strong>American</strong> Forest & Paper Association, Inc. For information on permission to copy material, please contact:<br />
Copyright Permission<br />
AF&PA <strong>American</strong> <strong>Wood</strong> <strong>Council</strong><br />
1111 Nineteenth St., NW, Suite 800<br />
Washington, DC 20036<br />
email: awcinfo@afandpa.org<br />
Printed in the United States of America<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
iii<br />
Foreword<br />
This Allowable Stress Design/Load and Resistance<br />
Factor Design <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction<br />
(<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong>) provides guidance for design of most<br />
wood-based structural products used in the construction<br />
of wood buildings. The complete <strong>Wood</strong> Design Package<br />
includes this <strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> and the following:<br />
• ANSI/AF&PA NDS-2005 National Design Specification<br />
® (NDS ® ) for <strong>Wood</strong> Construction – with<br />
Commentary; and, NDS Supplement – Design Values<br />
for <strong>Wood</strong> Construction, 2005 Edition,<br />
• ANSI/AF&PA SDPWS-05 – Special Design Provisions<br />
for Wind and Seismic (SDPWS) – with<br />
Commentary,<br />
• <strong>ASD</strong>/<strong>LRFD</strong> Structural <strong>Wood</strong> Design Solved Example<br />
Problems, 2005 Edition.<br />
products for over 70 years, first in the form of the <strong>Wood</strong><br />
Structural Design Data series and then in the National<br />
Design Specification (NDS) for <strong>Wood</strong> Construction.<br />
It is intended that this document be used in conjunction<br />
with competent engineering design, accurate fabrication,<br />
and adequate supervision of construction. AF&PA does not<br />
assume any responsibility for errors or omissions in the<br />
document, nor for engineering designs, plans, or construction<br />
prepared from it.<br />
Those using this standard assume all liability arising<br />
from its use. The design of engineered structures is within<br />
the scope of expertise of licensed engineers, architects, or<br />
other licensed professionals for applications to a particular<br />
structure.<br />
<strong>American</strong> Forest & Paper Association<br />
The <strong>American</strong> Forest & Paper Association (AF&PA)<br />
has developed this manual for design professionals.<br />
AF&PA and its predecessor organizations have provided<br />
engineering design information to users of structural wood<br />
<strong>American</strong> Forest & paper association
iv<br />
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
<br />
TABLE OF CONTENTS<br />
Part/Title Page Part/Title Page<br />
M1<br />
M2<br />
M3<br />
M4<br />
M5<br />
M6<br />
GENERAL REQUIREMENTS<br />
FOR STRUCTURAL DESIGN............1<br />
M1.1 Products Covered in This <strong>Manual</strong><br />
M1.2 General Requirements<br />
M1.3 Design Procedures<br />
DESIGN VALUES FOR<br />
STRUCTURAL MEMBERS.................. 3<br />
M2.1 General Information<br />
M2.2 Reference Design Values<br />
M2.3 Adjustment of Design Values<br />
DESIGN PROVISIONS AND<br />
EQUATIONS........................................................ 5<br />
M3.1 General<br />
M3.2 Bending Members - General<br />
M3.3 Bending Members - Flexure<br />
M3.4 Bending Members - Shear<br />
M3.5 Bending Members - Deflection<br />
M3.6 Compression Members<br />
M3.7 Solid Columns<br />
M3.8 Tension Members<br />
M3.9 Combined Bending and Axial Loading<br />
M3.10 Design for Bearing<br />
SAWN LUMBER...........................................11<br />
M4.1 General<br />
M4.2 Reference Design Values<br />
M4.3 Adjustment of Reference Design<br />
Values<br />
M4.4 Special Design Considerations<br />
M4.5 Member Selection Tables<br />
M4.6 Examples of Capacity Table<br />
Development<br />
STRUCTURAL GLUED<br />
LAMINATED TIMBER............................27<br />
M5.1 General<br />
M5.2 Reference Design Values<br />
M5.3 Adjustment of Reference Design<br />
Values<br />
M5.4 Special Design Considerations<br />
ROUND TIMBER POLES<br />
AND PILES...................................................... 33<br />
M6.1 General<br />
M6.2 Reference Design Values<br />
M6.3 Adjustment of Reference Design<br />
Values<br />
M6.4 Special Design Considerations<br />
M7<br />
M8<br />
M9<br />
PREFABRICATED WOOD<br />
I-JOISTS.............................................................37<br />
M7.1 General<br />
M7.2 Reference Design Values<br />
M7.3 Adjustment of Reference Design<br />
Values<br />
M7.4 Special Design Considerations<br />
STRUCTURAL COMPOSITE<br />
LUMBER.............................................................. 53<br />
M8.1 General<br />
M8.2 Reference Design Values<br />
M8.3 Adjustment of Reference Design<br />
Values<br />
M8.4 Special Design Considerations<br />
WOOD STRUCTURAL<br />
PANELS................................................................59<br />
M9.1 General<br />
M9.2 Reference Design Values<br />
M9.3 Adjustment of Reference Design<br />
Values<br />
M9.4 Special Design Considerations<br />
M10 MECHANICAL<br />
CONNECTIONS............................................69<br />
M10.1 General<br />
M10.2 Reference Design Values<br />
M10.3 Design Adjustment Factors<br />
M10.4 Typical Connection Details<br />
M10.5 Pre-Engineered Metal Connectors<br />
M11 DOWEL-TYPE FASTENERS........ 85<br />
M11.1 General<br />
M11.2 Reference Withdrawal Design<br />
Values<br />
M11.3 Reference Lateral Design Values<br />
M11.4 Combined Lateral and Withdrawal<br />
Loads<br />
M11.5 Adjustment of Reference Design<br />
Values<br />
M11.6 Multiple Fasteners<br />
M12 SPLIT RING AND SHEAR<br />
PLATE CONNECTORS........................ 89<br />
M12.1 General<br />
M12.2 Reference Design Values<br />
M12.3 Placement of Split Ring and Shear<br />
Plate Connectors<br />
<strong>American</strong> Forest & paper association
vi<br />
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
Part/Title Page Part/Title Page<br />
M13 TIMBER RIVETS........................................91<br />
M13.1 General<br />
M13.2 Reference Design Values<br />
M13.3 Placement of Timber Rivets<br />
M14 SHEAR WALLS AND<br />
DIAPHRAGMS............................................. 93<br />
M14.1 General<br />
M14.2 Design Principles<br />
M14.3 Shear Walls<br />
M14.4 Diaphragms<br />
M15 SPECIAL LOADING<br />
CONDITIONS.................................................99<br />
M15.1 Lateral Distribution of<br />
Concentrated Loads<br />
M15.2 Spaced Columns<br />
M15.3 Built-Up Columns<br />
M15.4 <strong>Wood</strong> Columns with Side Loads<br />
and Eccentricity<br />
M16 FIRE DESIGN.............................................101<br />
M16.1 General<br />
M16.2 Design Procedures for Exposed<br />
<strong>Wood</strong> Members<br />
M16.3 <strong>Wood</strong> Connections<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
vii<br />
LIST OF TABLES<br />
M4.3-1<br />
M4.4-1<br />
Applicability of Adjustment Factors for<br />
Sawn Lumber.............................................. 13<br />
Approximate Moisture and Thermal<br />
Dimensional Changes................................. 14<br />
M4.4-2 Coefficient of Moisture Expansion, e ME ,<br />
and Fiber Saturation Point, FSP, for Solid<br />
<strong>Wood</strong>s......................................................... 15<br />
M4.4-3<br />
M4.5-1a<br />
Coefficient of Thermal Expansion, e TE , for<br />
Solid <strong>Wood</strong>s................................................ 16<br />
<strong>ASD</strong> Tension Member Capacity (T'),<br />
Structural Lumber (2-inch nominal thickness<br />
Visually Graded Lumber (1.5 inch dry<br />
dressed size), C D = 1.0.4-inch nominal<br />
thickness Visually Graded Lumber (3.5<br />
inch dry dressed size), C D = 1.0)................. 18<br />
M4.5-1b <strong>ASD</strong> Tension Member Capacity (T'),<br />
Structural Lumber (2-inch nominal<br />
thickness MSR Lumber (1.5 inch dry<br />
dressed size), C D = 1.0)............................... 18<br />
M4.5-2a<br />
<strong>ASD</strong> Column Capacity (P', P' x , P' y ), Timbers<br />
(6-inch nominal thickness (5.5 inch dry<br />
dressed size), C D = 1.0)............................... 19<br />
M4.5-2b <strong>ASD</strong> Column Capacity (P', P' x , P' y ), Timbers<br />
(8-inch nominal thickness (7.5 inch dry<br />
dressed size), C D = 1.0)............................... 20<br />
M4.5-2c<br />
M4.5-3a<br />
<strong>ASD</strong> Column Capacity (P', P' x , P' y ), Timbers<br />
(10-inch nominal thickness (9.5 inch dry<br />
dressed size), C D = 1.0)............................... 21<br />
<strong>ASD</strong> Bending Member Capacity (M',<br />
C r M', V', and EI), Structural Lumber (2-inch<br />
nominal thickness (1.5 inch dry dressed<br />
size), C D = 1.0, C L = 1.0)............................. 22<br />
M4.5-3b <strong>ASD</strong> Bending Member Capacity (M', C r M',<br />
V', and EI), Structural Lumber (4-inch<br />
nominal thickness (3.5 inch dry dressed<br />
size), C D = 1.0, C L = 1.0.............................. 22<br />
M4.5-4a<br />
<strong>ASD</strong> Bending Member Capacity (M', V',<br />
and EI), Timbers (6-inch nominal thickness<br />
(5.5 inch dry dressed size), C D = 1.0,<br />
C L = 1.0)...................................................... 23<br />
M4.5-4b <strong>ASD</strong> Bending Member Capacity (M', V',<br />
and EI), Timbers (8-inch nominal<br />
thickness (7.5 inch dry dressed size),<br />
C D = 1.0, C L = 1.0)...................................... 23<br />
M4.5-4c<br />
<strong>ASD</strong> Bending Member Capacity (M', V',<br />
and EI), Timbers (10-inch nominal<br />
thickness (9.5 inch dry dressed size),<br />
C D = 1.0, C L = 1.0)...................................... 24<br />
M4.5-4d <strong>ASD</strong> Bending Member Capacity (M', V',<br />
and EI), Timbers (Nominal dimensions ><br />
10 inch (actual = nominal – 1/2 inch),<br />
C D = 1.0, C L = 1.0)...................................... 24<br />
M5.1-1<br />
M5.3-1<br />
M5.4-1<br />
M6.3-1<br />
M7.3-1<br />
M8.3-1<br />
Economical Spans for Structural Glued<br />
Laminated Timber Framing Systems.......... 29<br />
Applicability of Adjustment Factors for<br />
Structural Glued Laminated Timber........... 31<br />
Average Specific Gravity and Weight<br />
Factor.......................................................... 32<br />
Applicability of Adjustment Factors for<br />
Round Timber Poles and Piles.................... 35<br />
Applicability of Adjustment Factors for<br />
Prefabricated <strong>Wood</strong> I-Joists........................ 40<br />
Applicability of Adjustment Factors for<br />
Structural Composite Lumber..................... 56<br />
M9.1-1 Guide to Panel Use..................................... 61<br />
M9.2-1<br />
M9.2-2<br />
M9.2-3<br />
M9.2-4<br />
M9.3-1<br />
<strong>Wood</strong> Structural Panel Bending Stiffness<br />
and Strength................................................ 62<br />
<strong>Wood</strong> Structural Panel Axial Stiffness,<br />
Tension, and Compression Capacities........ 63<br />
<strong>Wood</strong> Structural Panel Planar (Rolling)<br />
Shear Capacities.......................................... 65<br />
<strong>Wood</strong> Structural Panel Rigidity and<br />
Through-the-Thickness Shear Capacities... 65<br />
Applicability of Adjustment Factors for<br />
<strong>Wood</strong> Structural Panels............................... 66<br />
M9.4-1 Panel Edge Support..................................... 67<br />
M9.4-2<br />
Minimum Nailing for <strong>Wood</strong> Structural<br />
Panel Applications...................................... 68<br />
M10.3-1 Applicability of Adjustment Factors for<br />
Mechanical Connections............................. 71<br />
<strong>American</strong> Forest & paper association
viii<br />
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
M11.3-1<br />
Applicability of Adjustment Factors for<br />
Dowel-Type Fasteners................................ 87<br />
M12.2-1 Applicability of Adjustment Factors for<br />
Split Ring and Shear Plate Connectors....... 90<br />
M13.2-1 Applicability of Adjustment Factors for<br />
Timber Rivets............................................. 92<br />
M16.1-1 Minimum Sizes to Qualify as Heavy<br />
Timber Construction................................. 102<br />
M16.1-2 One-Hour Fire-Rated Load-Bearing<br />
<strong>Wood</strong>-Frame Wall Assemblies....................103<br />
M16.1-3 Two-Hour Fire-Rated Load-Bearing<br />
<strong>Wood</strong>-Frame Wall Assemblies.................. 103<br />
M16.1-4 One-Hour Fire-Rated <strong>Wood</strong> Floor/Ceiling<br />
Assemblies................................................ 104<br />
M16.1-5 Two-Hour Fire-Rated <strong>Wood</strong> Floor/Ceiling<br />
Assemblies................................................ 104<br />
M16.1-6 Minimum Depths at Which Selected Beam<br />
Sizes Can Be Adopted for One-Hour Fire<br />
Ratings...................................................... 119<br />
M16.1-7 Fire-Resistive <strong>Wood</strong> I-Joist Floor/Ceiling<br />
Assemblies................................................ 123<br />
M16.1-8 Privacy Afforded According to STC<br />
Rating........................................................ 143<br />
M16.1-9 Contributions of Various Products to STC<br />
or IIC Rating............................................. 143<br />
M16.1-10 Example Calculation................................. 144<br />
M16.1-11 STC & IIC Ratings for UL L528/L529.... 144<br />
M16.1-12 STC & IIC Ratings for FC-214................ 144<br />
M16.2-1 Design Load Ratios for Bending<br />
Members Exposed on Three Sides<br />
(Structural Calculations at Standard<br />
Reference Conditions: C D = 1.0, C M = 1.0,<br />
C t = 1.0, C i = 1.0, C L = 1.0) (Protected<br />
Surface in Depth Direction)...................... 147<br />
M16.2-2 Design Load Ratios for Bending Members<br />
Exposed on Four Sides (Structural<br />
Calculations at Standard Reference<br />
Conditions: C D = 1.0, C M = 1.0, C t = 1.0,<br />
C i = 1.0, C L =1.0)..............................................148<br />
M16.2-3 Design Load Ratios for Compression<br />
Members Exposed on Three Sides<br />
(Structural Calculations at Standard<br />
Reference Conditions: C M = 1.0, C t = 1.0,<br />
C i = 1.0) (Protected Surface in Depth<br />
Direction).................................................. 149<br />
M16.2-4 Design Load Ratios for Compression<br />
Members Exposed on Three Sides<br />
(Structural Calculations at Standard<br />
Reference Conditions: C M = 1.0, C t = 1.0,<br />
C i = 1.0) (Protected Surface in Width<br />
Direction).................................................. 150<br />
M16.2-5 Design Load Ratios for Compression<br />
Members Exposed on Four Sides<br />
(Structural Calculations at Standard<br />
Reference Conditions: C M = 1.0, C t = 1.0,<br />
C i = 1.0).................................................... 151<br />
M16.2-6 Design Load Ratios for Tension Members<br />
Exposed on Three Sides (Structural<br />
Calculations at Standard Reference<br />
Conditions: C D = 1.0, C M = 1.0, C t = 1.0,<br />
C i = 1.0) (Protected Surface in Depth<br />
Direction).................................................. 152<br />
M16.2-7 Design Load Ratios for Tension Members<br />
Exposed on Three Sides (Structural<br />
Calculations at Standard Reference<br />
Conditions: C D = 1.0, C M = 1.0, C t = 1.0,<br />
C i = 1.0) (Protected Surface in Width<br />
Direction).................................................. 153<br />
M16.2-8 Design Load Ratios for Tension Members<br />
Exposed on Four Sides (Structural<br />
Calculations at Standard Reference<br />
Conditions: C D = 1.0, C M = 1.0, C t = 1.0,<br />
C i = 1.0).................................................... 154<br />
M16.2-9 Design Load Ratios for Exposed Timber<br />
Decks (Double and Single Tongue &<br />
Groove Decking) (Structural Calculations<br />
at Standard Reference Conditions:<br />
C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)...... 155<br />
M16.2-10 Design Load Ratios for Exposed Timber<br />
Decks (Butt-Joint Timber Decking)<br />
(Structural Calculations at Standard<br />
Reference Conditions: C D = 1.0, C M = 1.0,<br />
C t = 1.0, C i = 1.0)...................................... 155<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
ix<br />
LIST OF FIGURES<br />
M5.1-1<br />
Unbalanced and Balanced Layup<br />
Combinations.............................................. 28<br />
M5.2-1 Loading in the X-X and Y-Y Axes.............. 30<br />
M7.4-1 Design Span Determination........................ 41<br />
M7.4-2 Load Case Evaluations............................... 43<br />
M7.4-3<br />
End Bearing Web Stiffeners (Bearing<br />
Block)......................................................... 45<br />
M7.4-4 Web Stiffener Bearing Interface................. 46<br />
M7.4-5 Beveled End Cut......................................... 46<br />
M7.4-6 Sloped Bearing Conditions (Low End)....... 47<br />
M7.4-7 Sloped Bearing Conditions (High End)...... 48<br />
M7.4-8<br />
Lateral Support Requirements for Joists<br />
in Hangers .................................................. 49<br />
M7.4-9 Top Flange Hanger Support........................ 49<br />
M7.4-10 Connection Requirements for Face Nail<br />
Hangers....................................................... 50<br />
M7.4-11 Details for Vertical Load Transfer.............. 51<br />
M9.2-1<br />
Structural Panel with Strength Direction<br />
Across Supports.......................................... 60<br />
M9.2-2 Example of Structural Panel in Bending.... 60<br />
M9.2-3<br />
M9.2-4<br />
M9.2-5<br />
Structural Panel with Axial Compression<br />
Load in the Plane of the Panel.................... 64<br />
Through-the-Thickness Shear for <strong>Wood</strong><br />
Structural Panels................................................. 64<br />
Planar (Rolling) Shear or Shear-in-the-<br />
Plane for <strong>Wood</strong> Structural Panels............... 64<br />
M14.2-1 Shear Wall Drag Strut................................. 94<br />
M14.2-2 Shear Wall Special Case Drag Strut........... 95<br />
M14.2-3 Diaphragm Drag Strut (Drag strut parallel<br />
to loads)...................................................... 95<br />
M14.2-4 Diaphragm Chord Forces............................ 96<br />
M14.3-1 Overturning Forces (no dead load)............. 97<br />
M14.3-2 Overturning Forces (with dead load).......... 97<br />
M16.1-1 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS4-1.1) (2x4 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)....................................... 105<br />
M16.1-2 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-1.1) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)....................................... 106<br />
M16.1-3 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-1.2) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)....................................... 107<br />
M16.1-4 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-1.4) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)....................................... 108<br />
M16.1-5 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS4-1.2) (2x4 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251........................................ 109<br />
M16.1-6 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS4-1.3) (2x4 <strong>Wood</strong> Stud<br />
Wall - 78% Design Load - ASTM<br />
E119/NFPA 251)....................................... 110<br />
M16.1-7 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-1.3) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)........................................111<br />
M16.1-8 One-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-1.5) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 25)......................................... 112<br />
M16.1-9 Two-Hour Fire-Resistive <strong>Wood</strong> Wall<br />
Assembly (WS6-2.1) (2x6 <strong>Wood</strong> Stud<br />
Wall - 100% Design Load - ASTM<br />
E119/NFPA 251)....................................... 113<br />
M16.1-10 One-Hour Fire-Resistive <strong>Wood</strong><br />
Floor/Ceiling Assembly (2x10 <strong>Wood</strong> Joists<br />
16" o.c. – Gypsum Directly Applied or on<br />
Optional Resilient Channels).................... 114<br />
<strong>American</strong> Forest & paper association
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
M16.1-11 One-Hour Fire-Resistive <strong>Wood</strong><br />
Floor/Ceiling Assembly (2x10 <strong>Wood</strong> Joists<br />
16" o.c. – Suspended Acoustical Ceiling<br />
Panels)....................................................... 115<br />
M16.1-12 One-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling<br />
Assembly (2x10 <strong>Wood</strong> Joists 16" o.c.<br />
– Gypsum on Resilient Channels)............ 116<br />
M16.1-13 One-Hour Fire-Resistive <strong>Wood</strong><br />
Floor/Ceiling Assembly (2x10 <strong>Wood</strong><br />
Joists 24" o.c. – Gypsum on Resilient<br />
Channels).................................................. 117<br />
M16.1-14 Two-Hour Fire-Resistive <strong>Wood</strong><br />
Floor/Ceiling Assembly (2x10 <strong>Wood</strong><br />
Joists 16" o.c. – Gypsum Directly Applied<br />
with Second Layer on Resilient<br />
Channels).................................................. 118<br />
M16.1-15 One-Hour Fire-Resistive Ceiling Assembly<br />
(WIJ-1.1) (Floor/Ceiling - 100% Design<br />
Load - 1-Hour Rating - ASTM<br />
E119/NFPA 251)....................................... 124<br />
M16.1-16 One-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-1.2) (Floor/Ceiling -<br />
100% Design Load - 1 Hour Rating -<br />
ASTM E119/NFPA 251)........................... 125<br />
M16.1-17 One-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-1.3) (Floor/Ceiling -<br />
100% Design Load - 1-Hour Rating -<br />
ASTM E119/NFPA 251)........................... 126<br />
M16.1-18 One-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-1.4) (Floor/Ceiling -<br />
100% Design Load - 1-Hour Rating -<br />
ASTM E119/NFPA 251)........................... 127<br />
M16.1-19 One-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-1.5) (Floor/Ceiling -<br />
100% Design Load - 1-Hour Rating -<br />
ASTM E119/NFPA 251)........................... 128<br />
M16.1-20 One-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-1.6) (Floor/Ceiling -<br />
100% Design Load - 1-Hour Rating -<br />
ASTM E119/NFPA 251)........................... 129<br />
M16.1-21 Two-Hour Fire-Resistive Ceiling<br />
Assembly (WIJ-2.1) (Floor/Ceiling -<br />
100% Design Load - 2-Hour Rating -<br />
ASTM E119/NFPA 251)........................... 130<br />
M16.1-22 Cross Sections of Possible One-Hour<br />
Area Separations....................................... 139<br />
M16.1-23 Examples of Through-Penetration<br />
Firestop Systems....................................... 142<br />
M16.3-1 Beam to Column Connection -<br />
Connection Not Exposed to Fire............... 159<br />
M16.3-2 Beam to Column Connection - Connection<br />
Exposed to Fire Where Appearance is a<br />
Factor........................................................ 159<br />
M16.3-3 Ceiling Construction ................................ 159<br />
M16.3-4 Beam to Column Connection - Connection<br />
Exposed to Fire Where Appearance is<br />
Not a Factor.............................................. 159<br />
M16.3-5 Column Connections Covered ................. 160<br />
M16.3-6 Beam to Girder - Concealed<br />
Connection................................................ 160<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction<br />
<br />
M1: GENERAL<br />
REQUIREMENTS<br />
FOR<br />
STRUCTURAL<br />
DESIGN<br />
1<br />
M1.1 Products Covered in This <strong>Manual</strong> 2<br />
M1.2 General Requirements 2<br />
M1.2.1 Bracing 2<br />
M1.3 Design Procedures 2<br />
<strong>American</strong> Forest & paper association
M1: general requirements for structural design<br />
M1.1 Products Covered in This <strong>Manual</strong><br />
This <strong>Manual</strong> was developed with the intention of covering<br />
all structural applications of wood-based products<br />
and their connections that meet the requirements of the<br />
referenced standards. The <strong>Manual</strong> is a dual format document<br />
incorporating design provisions for both allowable<br />
stress design (<strong>ASD</strong>) and load and resistance factor design<br />
(<strong>LRFD</strong>). Design information is available for the following<br />
list of products. Each product chapter contains information<br />
for use with this <strong>Manual</strong> and the National Design Specification®<br />
(NDS®) for <strong>Wood</strong> Construction. Chapters are<br />
organized to parallel the chapter format of the NDS.<br />
• Sawn Lumber Chapter 4<br />
• Structural Glued Laminated Timber Chapter 5<br />
• Round Timber Poles and Piles Chapter 6<br />
• Prefabricated <strong>Wood</strong> I-Joists Chapter 7<br />
• Structural Composite Lumber Chapter 8<br />
• <strong>Wood</strong> Structural Panels Chapter 9<br />
• Mechanical Connections Chapter 10<br />
• Dowel-Type Fasteners Chapter 11<br />
• Split Ring and Shear Plate Connectors Chapter 12<br />
• Timber Rivets Chapter 13<br />
• Shear Walls and Diaphragms Chapter 14<br />
An additional Supplement, entitled Special Design<br />
Provisions for Wind and Seismic (SDPWS), has been<br />
developed to cover materials, design, and construction of<br />
wood members, fasteners, and assemblies to resist wind<br />
and seismic forces.<br />
M1.2 General Requirements<br />
This <strong>Manual</strong> is organized as a multi-part package for<br />
maximum flexibility for the design engineer. Included in<br />
this package are:<br />
• NDS and Commentary; and, NDS Supplement:<br />
Design Values for <strong>Wood</strong> Construction,<br />
• Special Design Provisions for Wind and Seismic<br />
(SDPWS) and Commentary,<br />
• Structural <strong>Wood</strong> Design Solved Example Problems.<br />
M1.2.1 Bracing<br />
Design considerations related to both temporary and<br />
permanent bracing differ among product types. Specific<br />
discussion of bracing is included in the product chapter.<br />
M1.3 Design Procedures<br />
The NDS is a dual format specification incorporating<br />
design provisions for <strong>ASD</strong> and <strong>LRFD</strong>. Behavioral equations,<br />
such as those for member and connection design, are<br />
the same for both <strong>ASD</strong> and <strong>LRFD</strong>. Adjustment factor tables<br />
include applicable factors for determining an adjusted <strong>ASD</strong><br />
design value or an adjusted <strong>LRFD</strong> design value. NDS<br />
Appendix N – (Mandatory) Load and Resistance Factor<br />
Design (<strong>LRFD</strong>) outlines requirements that are unique to<br />
<strong>LRFD</strong> and adjustment factors for <strong>LRFD</strong>.<br />
The basic design equations for <strong>ASD</strong> or <strong>LRFD</strong> require<br />
that the specified product reference design value meet or<br />
exceed the actual (applied) stress or other effect imposed<br />
by the specified loads. In <strong>ASD</strong>, the reference design values<br />
are set very low, and the nominal load magnitudes are set<br />
at once-in-a-lifetime service load levels. This combination<br />
produces designs that maintain high safety levels yet<br />
remain economically feasible.<br />
From a user’s standpoint, the design process is similar<br />
using <strong>LRFD</strong>. The most obvious difference between<br />
<strong>LRFD</strong> and <strong>ASD</strong> is that both the adjusted design values<br />
and load effect values in <strong>ASD</strong> will be numerically much<br />
lower than in <strong>LRFD</strong>. The adjusted design values are lower<br />
because they are reduced by significant internal safety<br />
adjustments. The load effects are lower because they are<br />
nominal (service) load magnitudes. The load combination<br />
equations for use with <strong>ASD</strong> and <strong>LRFD</strong> are given in the<br />
model building codes.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction<br />
<br />
M2: DESIGN<br />
VALUES FOR<br />
STRUCTURAL<br />
MEMBERS<br />
2<br />
M2.1 General Information 4<br />
M2.2 Reference Design Values 4<br />
M2.3 Adjustment of Design Values 4<br />
<strong>American</strong> Forest & paper association
M2: DESIGN VALUES FOR STRUCTURAL MEMBERS<br />
M2.1 General Information<br />
Structural wood products are provided to serve a wide<br />
range of end uses. Some products are marketed through<br />
commodity channels where the products meet specific<br />
standards and the selection of the appropriate product is<br />
the responsibility of the user.<br />
Other products are custom manufactured to meet the<br />
specific needs of a given project. Products in this category<br />
are metal plate connected wood trusses and custom structural<br />
glued laminated timbers. Design of the individual<br />
members is based on criteria specified by the architect or<br />
engineer of record on the project. Manufacture of these<br />
products is performed in accordance with the product’s<br />
manufacturing standards. Engineering of these products<br />
normally only extends to the design of the products<br />
themselves. Construction-related issues, such as load path<br />
analysis and erection bracing, remain the responsibility of<br />
the professional of record for the project.<br />
M2.2 Reference Design Values<br />
Reference design value designates the allowable<br />
stress design value based on normal load duration. To<br />
avoid confusion, the descriptor “reference” is used and<br />
serves as a reminder that design value adjustment factors<br />
are applicable for design values in accordance with referenced<br />
conditions specified in the NDS – such as normal<br />
load duration.<br />
Reference design values for sawn lumber and structural<br />
glued laminated timber are contained in the NDS<br />
Supplement: Design Values for <strong>Wood</strong> Construction. Reference<br />
design values for round timber poles and piles,<br />
dowel-type fasteners, split ring and shear plate connectors,<br />
and timber rivets are contained in the NDS. Reference design<br />
values for all other products are typically contained<br />
in the manufacturer’s code evaluation report.<br />
M2.3 Adjustment of Design Values<br />
Adjusted design value designates reference design<br />
values which have been multiplied by adjustment factors.<br />
Basic requirements for design use terminology applicable<br />
to both <strong>ASD</strong> and <strong>LRFD</strong>. In equation format, this takes the<br />
standard form f b ≤ F b ′ which is applicable to either <strong>ASD</strong> or<br />
<strong>LRFD</strong>. Reference design values (F b , F t , F v , F c , F c , E, E min )<br />
are multiplied by adjustment factors to determine adjusted<br />
design values (F b ′, F t ′, F v ′, F c ′, F c ′, E′, E min ′).<br />
Reference conditions have been defined such that a<br />
majority of wood products used in interior or in protected<br />
environments will require no adjustment for moisture,<br />
temperature, or treatment effects.<br />
Moisture content (MC) reference conditions are 19%<br />
or less for sawn lumber products. The equivalent limit for<br />
glued products (structural glued laminated timber, structural<br />
composite lumber, prefabricated wood I-joists, and<br />
wood structural panels) is defined as 16% MC or less.<br />
Temperature reference conditions include sustained<br />
temperatures up to 100ºF. Note that it has been traditionally<br />
assumed that these reference conditions also include<br />
common building applications in desert locations where<br />
daytime temperatures will often exceed 100ºF. Examples<br />
of applications that may exceed the reference temperature<br />
range include food processing or other industrial buildings.<br />
Tabulated design values and capacities are for untreated<br />
members. Tabulated design values and capacities<br />
also apply to wood products pressure treated by an approved<br />
process and preservative except as specified for<br />
load duration factors.<br />
An unincised reference condition is assumed. For<br />
members that are incised to increase penetration of preservative<br />
chemicals, use the incising adjustment factors<br />
given in the product chapter.<br />
The effects of fire retardant chemical treatment on<br />
strength shall be accounted for in the design. Reference<br />
design values, including connection design values, for<br />
lumber and structural glued laminated timber pressuretreated<br />
with fire retardant chemicals shall be obtained<br />
from the company providing the treatment and redrying<br />
service. The impact load duration factor shall not apply<br />
to structural members pressure-treated with fire retardant<br />
chemicals.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction<br />
<br />
M3: DESIGN<br />
PROVISIONS<br />
AND EQUATIONS<br />
3<br />
M3.1 General 6<br />
M3.2 Bending Members - General 6<br />
M3.3 Bending Members - Flexure 6<br />
M3.4 Bending Members - Shear 6<br />
M3.5 Bending Members - Deflection 7<br />
M3.6 Compression Members 7<br />
M3.7 Solid Columns 8<br />
M3.8 Tension Members 8<br />
M3.8.1 Tension Parallel to Grain 8<br />
M3.8.2 Tension Perpendicular to Grain 8<br />
M3.9 Combined Bending and Axial Loading 9<br />
M3.10 Design for Bearing 10<br />
<strong>American</strong> Forest & paper association
M3: Design Provisions and Equations<br />
M3.1 General<br />
This Chapter covers design of members for bending,<br />
compression, tension, combined bending and axial loads,<br />
and bearing.<br />
M3.2 Bending Members - General<br />
This section covers design of members stressed primarily<br />
in flexure (bending). Examples of such members<br />
include primary framing members (beams) and secondary<br />
framing members (purlins, joists). Products commonly<br />
used in these applications include glulam, solid sawn<br />
lumber, structural composite lumber, and prefabricated<br />
I‐joists.<br />
Bending members are designed so that no design capacity<br />
is exceeded under applied loads. Strength criteria<br />
for bending members include bending moment, shear, local<br />
buckling, lateral torsional buckling, and bearing.<br />
See specific product chapters for moment and shear<br />
capacities (joist and beam selection tables) and reference<br />
bending and shear design values.<br />
M3.3 Bending Members - Flexure<br />
The basic equation for moment design of bending<br />
members is:<br />
M′ ≥ M (M3.3-1)<br />
where:<br />
M′ = adjusted moment capacity<br />
M = bending moment<br />
The equation for calculation of adjusted moment<br />
capacity is:<br />
M′ = F b ′ S (M3.3-2)<br />
where:<br />
S = section modulus, in. 3<br />
F b ′ = adjusted bending design value, psi.<br />
See product chapters for applicable<br />
adjustment factors.<br />
M3.4 Bending Members - Shear<br />
The basic equation for shear design of bending members<br />
is:<br />
V′ ≥ V (M3.4-1)<br />
where:<br />
V′ = adjusted shear capacity parallel to<br />
grain, lbs<br />
V = shear force, lbs<br />
The equation for calculation of shear capacity is:<br />
V′ = F v ′ Ib/Q (M3.4-2)<br />
which, for rectangular unnotched bending members,<br />
reduces to:<br />
V′ = 2/3 (F v ′) A (M3.4-3)<br />
where:<br />
I = moment of inertia, in. 4<br />
A = area, in. 2<br />
F v ′ = adjusted shear design value, psi.<br />
See product chapters for applicable<br />
adjustment factors.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
<br />
M3.5 Bending Members - Deflection<br />
Users should note that design of bending members is<br />
often controlled by serviceability limitations rather than<br />
strength. Serviceability considerations, such as deflection<br />
and vibration, are often designated by the authority having<br />
jurisdiction.<br />
For a simple span uniformly loaded rectangular member,<br />
the equation used for calculating mid-span deflection is:<br />
∆ = 5 4<br />
w (M3.5-1)<br />
384EI<br />
where:<br />
∆ = deflection, in.<br />
w = uniform load, lb/in.<br />
= span, in.<br />
E I = stiffness of beam section, lb-in. 2<br />
M3.6 Compression Members<br />
This section covers design of members stressed primarily<br />
in compression parallel to grain. Examples of such<br />
members include columns, truss members, and diaphragm<br />
chords.<br />
Information in this section is limited to the case in<br />
which loads are applied concentrically to the member.<br />
Provisions of NDS 3.9 or NDS Chapter 15 should be used<br />
if loads are eccentric or if the compressive forces are applied<br />
in addition to bending forces.<br />
The NDS differentiates between solid, built-up, and<br />
spaced columns. In this context built-up columns are<br />
assembled from multiple pieces of similar members connected<br />
in accordance with NDS 15.3.<br />
A spaced column must comply with provisions of NDS<br />
15.2. Note that this definition includes main column elements,<br />
spacer blocks with their connectors and end blocks<br />
with shear plate or split ring connectors.<br />
Compression Parallel to Grain<br />
The basic equation for design of compression members<br />
is:<br />
P′ ≥ P (M3.6-1)<br />
where:<br />
P′ = adjusted compression parallel to<br />
grain capacity, lbs<br />
P = compressive force, lbs<br />
Values of modulus of elasticity, E, and moment of<br />
inertia, I, for lumber and structural glued laminated timber<br />
for use in the preceding equation can be found in the NDS<br />
Supplement. Engineered wood products such as I-joists and<br />
structural composite lumber will have EI values published<br />
in individual manufacturer’s product literature or evaluation<br />
reports. Some manufacturers might publish “true” E<br />
which would require additional computations to account<br />
for shear deflection. See NDS Appendix F for information<br />
on shear deflection. See product chapters for more details<br />
about deflection calculations.<br />
The complete equation for calculation of adjusted<br />
compression capacity is:<br />
P′ = F c ′ A (M3.6-2)<br />
where:<br />
A = area, in. 2<br />
F c ′ = adjusted compression parallel to<br />
grain design value, psi. See product<br />
chapters for applicable adjustment<br />
factors.<br />
Special Considerations<br />
Net Section Calculation<br />
As in design of tension members, compression members<br />
should be checked both on a gross section and a net<br />
section basis (see NDS 3.6.3).<br />
Bearing Capacity Checks<br />
Design for bearing is addressed in NDS 3.10.<br />
Radial Compression in Curved Members<br />
Stresses induced in curved members under load include<br />
a component of stress in the direction of the radius<br />
of curvature. Radial compression is a specialized design<br />
consideration that is addressed in NDS 5.4.1.<br />
3<br />
M3: DESIGN PROVISIONS AND EQUATIONS<br />
<strong>American</strong> Forest & paper association
M3: Design Provisions and Equations<br />
M3.7 Solid Columns<br />
Slenderness Considerations and<br />
Stability<br />
The user is cautioned that stability calculations are<br />
highly dependent upon boundary conditions assumed in<br />
the analysis. For example, the common assumption of a<br />
pinned-pinned column is only accurate or conservative if<br />
the member is restrained against sidesway. If sidesway is<br />
possible and a pinned-free condition exists, the value of<br />
K e in NDS 3.7.1.2 doubles (see NDS Appendix Table G1<br />
for recommended buckling length coefficients, K e ) and the<br />
computed adjusted compression parallel to grain capacity<br />
decreases.<br />
M3.8 Tension Members<br />
This section covers design of members stressed<br />
primarily in tension parallel to grain. Examples of such<br />
members include shear wall end posts, truss members, and<br />
diaphragm chords.<br />
The designer is advised that use of wood members<br />
in applications that induce tension perpendicular to grain<br />
stresses should be avoided.<br />
M3.8.1 Tension Parallel to Grain<br />
is:<br />
where:<br />
The basic equation for design of tension members<br />
T′ ≥ T (M3.8-1)<br />
T′ = adjusted tension parallel to grain<br />
capacity, lbs<br />
T = tensile force, lbs<br />
The equation for calculation of adjusted tension capacity<br />
is:<br />
Net Section Calculation<br />
Design of tension members is often controlled by the<br />
ability to provide connections to develop tensile forces<br />
within the member. In the area of connections, one must<br />
design not only the connection itself (described in detail<br />
in Chapter M10) but also the transfer of force across the<br />
net section of the member. One method for determining<br />
these stresses is provided in NDS Appendix E.<br />
M3.8.2 Tension Perpendicular to<br />
Grain<br />
Radial Stress in Curved Members<br />
Stresses induced in curved members under load include<br />
a component of stress in the direction of the radius<br />
of curvature. This stress is traditionally called radial tension.<br />
Radial stress design is a specialized consideration<br />
that is covered in NDS 5.4.1 and is explained in detail in<br />
the <strong>American</strong> Institute of Timber Construction (AITC)<br />
Timber Construction <strong>Manual</strong>.<br />
T′ = F t ′A (M3.8-2)<br />
where:<br />
A = area, in. 2<br />
F t ′ = adjusted tension design value, psi.<br />
See product chapters for applicable<br />
adjustment factors.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
<br />
M3.9 Combined Bending and Axial Loading<br />
This section covers design of members stressed under<br />
combined bending and axial loads. The applicable strength<br />
criteria for these members is explicit in the NDS equations<br />
– limiting the sum of various stress ratios to less than or<br />
equal to unity.<br />
Bending and Axial Tension<br />
Members must be designed by multiplying all applicable<br />
adjustment factors by the reference design values<br />
for the product. See M3.3 and M3.6 for discussion of applicable<br />
adjustment factors for bending or compression,<br />
respectively.<br />
Design Techniques<br />
3<br />
For designs in which the axial load is in tension rather<br />
than compression, the designer should use NDS Equations<br />
3.9-1 and 3.9-2.<br />
Bending and Axial Compression<br />
The equation for design of members under bending<br />
plus compression loads is given below in terms of load<br />
and moment ratios:<br />
2<br />
⎛ P ⎞ M<br />
M<br />
⎜<br />
P′<br />
⎟<br />
⎝ ⎠<br />
+ 1<br />
2<br />
+<br />
≤1.<br />
0<br />
P<br />
M ′ ⎛ ⎞<br />
−<br />
P M<br />
⎜ ⎟<br />
P<br />
M ′ − − ⎛ 2<br />
⎡<br />
⎝ E ⎠ PE<br />
⎝ ⎜ ⎞ ⎤<br />
1<br />
1 1<br />
2<br />
⎢1 ⎟ ⎥ (M3.9-1)<br />
1<br />
M<br />
⎣⎢<br />
2 E ⎠ ⎦ ⎥<br />
where<br />
P′ = adjusted compression capacity<br />
determined per M3.6, lbs<br />
P = compressive force determined per<br />
M3.6, lbs<br />
M 1 ′ = adjusted moment capacity (strong<br />
axis) determined per M3.3, in.-lbs<br />
M 1 = bending moment (strong axis)<br />
determined per M3.3, in.-lbs<br />
M 2 ′ = adjusted moment capacity (weak<br />
axis) determined per M3.3, in.-lbs<br />
M 2 = bending moment (weak axis)<br />
determined per M3.3, in.-lbs<br />
P E1 = F cE1 A = critical column buckling<br />
capacity (strong axis) determined per<br />
NDS 3.9.2, lbs<br />
P E2 = F cE2 A = critical column buckling<br />
capacity (weak axis) determined per<br />
NDS 3.9.2, lbs<br />
M E = F bE S = critical beam buckling capacity<br />
determined per NDS 3.9.2, in.-lbs<br />
A key to understanding design of members under<br />
combined bending and axial loads is that components<br />
of the design equation are simple ratios of compressive<br />
force (or moment) to compression capacity (or moment<br />
capacity). Note that the compression term in this equation<br />
is squared. This is the result of empirical test data.<br />
Moderate compressive forces do not have as large an<br />
impact on capacity (under combined loads) as previously<br />
thought. It is believed that this is the result of compressive<br />
“reinforcing” of what would otherwise be a tensile failure<br />
mode in bending.<br />
M3: DESIGN PROVISIONS AND EQUATIONS<br />
<strong>American</strong> Forest & paper association
10 M3: Design Provisions and Equations<br />
M3.10 Design for Bearing<br />
Columns often transfer large forces within a structural<br />
system. While satisfaction of column strength criteria is<br />
usually the primary concern, the designer should also<br />
check force transfer at the column bearing.<br />
For cases in which the column is bearing on another<br />
wood member, especially if bearing is perpendicular to<br />
grain, this calculation will often control the design.<br />
The basic equation for bearing design is:<br />
R′ ≥ R (M3.10-1)<br />
where:<br />
R′ = adjusted compression perpendicular<br />
to grain capacity, lbs<br />
R = compressive force or reaction, lbs<br />
The equation for calculation of adjusted compression<br />
perpendicular to grain capacity is:<br />
R′ = F c ′ A (M3.10-2)<br />
where:<br />
A = area, in. 2<br />
F c ′ = adjusted compression perpendicular<br />
to grain design value, psi. See product<br />
chapters for applicable adjustment<br />
factors.<br />
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M4: SAWN<br />
LUMBER<br />
4<br />
M4.1 General 12<br />
M4.2 Reference Design Values 12<br />
M4.3 Adjustment of Reference<br />
Design Values 13<br />
M4.4 Special Design Considerations 14<br />
M4.5 Member Selection Tables 17<br />
M4.6 Examples of Capacity Table<br />
Development 25<br />
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12 M4: SAWN LUMBER<br />
M4.1 General<br />
Product Information<br />
Structural lumber products are well-known throughout<br />
the construction industry. The economic advantages<br />
of lumber often dictate its choice as a preferred building<br />
material.<br />
Lumber is available in a wide range of species, grades,<br />
sizes, and moisture contents. Structural lumber products<br />
are typically specified by either the stress level required<br />
or by the species, grade, and size required.<br />
This Chapter provides information for designing structural<br />
lumber products in accordance with the NDS.<br />
Common Uses<br />
Structural lumber and timbers have been a primary<br />
construction material throughout the world for many centuries.<br />
They are the most widely used framing material for<br />
housing in North America.<br />
In addition to use in housing, structural lumber finds<br />
broad use in commercial and industrial construction. Its<br />
high strength, universal availability, and cost saving attributes<br />
make it a viable option in most low- and mid-rise<br />
construction projects.<br />
Structural lumber is used as beams, columns, headers,<br />
joists, rafters, studs, and plates in conventional construction.<br />
In addition to its use in lumber form, structural lumber<br />
is used to manufacture structural glued laminated beams,<br />
trusses, and wood I-joists.<br />
Availability<br />
Structural lumber is a widely available construction<br />
material. However, to efficiently specify structural lumber<br />
for individual construction projects, the specifier should be<br />
aware of the species, grades, and sizes available locally.<br />
The best source of this information is your local lumber<br />
supplier.<br />
M4.2 Reference Design Values<br />
General<br />
The NDS Supplement provides reference design values<br />
for design of sawn lumber members. These design values<br />
are used when manual calculation of member capacity is<br />
required and must be used in conjunction with the adjustment<br />
factors specified in NDS 4.3.<br />
Reference Design Values<br />
Reference design values are provided in the NDS<br />
Supplement as follows:<br />
NDS<br />
Supplement<br />
Table Number<br />
4A and 4B<br />
4C<br />
4D<br />
4E<br />
4F<br />
Visually graded dimension lumber<br />
Mechanically graded dimension lumber<br />
Visually graded timbers<br />
Visually graded decking<br />
Non-North <strong>American</strong> visually graded<br />
dimension lumber<br />
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M4.3 Adjustment of Reference Design Values<br />
To generate member design capacities, reference design<br />
values for sawn lumber are multiplied by adjustment<br />
factors and section properties per Chapter M3. Applicable<br />
adjustment factors for sawn lumber are defined in NDS<br />
4.3. Table M4.3-1 shows the applicability of adjustment<br />
factors for sawn lumber in a slightly different format for<br />
the designer.<br />
Table M4.3-1<br />
Applicability of Adjustment Factors for Sawn Lumber<br />
4<br />
Allowable Stress Design<br />
F b ′ = F b C D C M C t C L C F C fu C i C r<br />
F t ′ = F t C D C M C t C F C i<br />
F v ′ = F v C D C M C t C i<br />
F c⊥ ′ = F c⊥ C M C t C i C b<br />
F c ′ = F c C D C M C t C F C i C P<br />
Load and Resistance Factor Design<br />
F b ′ = F b C M C t C L C F C fu C i C r K F φ b λ<br />
F t ′ = F t C M C t C F C i K F φ t λ<br />
F v ′ = F v C M C t C i K F φ v λ<br />
F c⊥ ′ = F c⊥ C M C t C i C b K F φ c λ<br />
F c ′ = F c C M C t C F C i C P K F φ c λ<br />
M4: SAWN LUMBER<br />
E′ = E C M C t C i E′ = E C M C t C i<br />
E min ′ = E min C M C t C i C T<br />
E min ′ = E min C M C t C i C T K F φ s<br />
Bending Member Example<br />
For unincised, straight, laterally supported bending<br />
members stressed in edgewise bending in single member<br />
use and used in a normal building environment (meeting<br />
the reference conditions of NDS 2.3 and 4.3), the adjusted<br />
design values reduce to:<br />
For <strong>ASD</strong>:<br />
F b ′ = F b C D C F<br />
F v ′ = F v C D<br />
F c⊥ ′ = F c⊥ C b<br />
E′ = E<br />
E min ′ = E min<br />
For <strong>LRFD</strong>:<br />
F b ′ = F b C F K F φ b λ<br />
Axially Loaded Member Example<br />
For unincised axially loaded members used in a normal<br />
building environment (meeting the reference conditions of<br />
NDS 2.3 and 4.3) designed to resist tension or compression<br />
loads, the adjusted tension or compression design values<br />
reduce to:<br />
For <strong>ASD</strong>:<br />
F c ′ = F c C D C F C P<br />
F t ′ = F t C D C F<br />
E min ′ = E min<br />
For <strong>LRFD</strong>:<br />
F c ′ = F c C F C P K F φ c λ<br />
F t ′ = F t C F K F φ t λ<br />
E min ′ = E min K F φ s<br />
F v ′ = F v K F φ v λ<br />
F c⊥ ′ = F c⊥ C b K F φ c λ<br />
E′ = E<br />
E min ′ = E min K F φ s<br />
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14 M4: SAWN LUMBER<br />
M4.4 Special Design Considerations<br />
General<br />
With proper detailing and protection, structural lumber<br />
can perform well in a variety of environments. One key to<br />
proper detailing is planning for the natural shrinkage and<br />
swelling of wood members as they are subjected to various<br />
drying and wetting cycles. While moisture changes have<br />
the largest impact on lumber dimensions, some designs<br />
must also check the effects of temperature on dimensions<br />
as well.<br />
Dimensional Changes<br />
Table M4.4-1 is extracted from more precise scientific<br />
and research reports on these topics. The coefficients are<br />
conservative (yielding more shrinkage and expansion<br />
than one might expect for most species). This level of<br />
information should be adequate for common structural applications.<br />
Equations are provided in this section for those<br />
designers who require more precise calculations.<br />
Design of wood members and assemblies for fire<br />
resistance is discussed in Chapter M16.<br />
Table M4.4-1<br />
Approximate Moisture and Thermal Dimensional Changes<br />
Description<br />
Dimensional change due to moisture content change 1<br />
Dimensional change due to temperature change 2<br />
Radial or Tangential Direction<br />
1% change in dimension per 4% change in MC<br />
20 × 10 -6 in./in. per degree F<br />
1. Corresponding longitudinal direction shrinkage/expansion is about 1% to 5% of that in radial and tangential directions.<br />
2. Corresponding longitudinal direction coefficient is about 1/10 as large as radial and tangential.<br />
Equations for Computing Moisture<br />
and Thermal Shrinkage/Expansion<br />
Due to Moisture Changes<br />
For more precise computation of dimensional changes<br />
due to changes in moisture, the change in radial (R), tangential<br />
(T), and volumetric (V) dimensions due to changes<br />
in moisture content can be calculated as:<br />
X X ∆ MC e<br />
(M4.4-1)<br />
= ( )<br />
o<br />
ME<br />
where:<br />
X 0 = initial dimension or volume<br />
Due to Temperature Changes<br />
For more precise calculation of dimensional changes<br />
due to changes in temperature, the shrinkage/expansion<br />
of solid wood including lumber and timbers can be calculated<br />
as:<br />
X X ∆ T e<br />
(M4.4-3)<br />
= ( )<br />
o<br />
TE<br />
where:<br />
X 0 = reference dimension at T 0<br />
X = computed dimension at T<br />
T 0 = reference temperature (°F)<br />
X = new dimension or volume<br />
∆MC = moisture content change (%)<br />
e ME = coefficient of moisture expansion:<br />
linear (in./in./%MC) or<br />
volumetric (in. 3 /in. 3 /%MC)<br />
and:<br />
T = temperature at which the new<br />
dimension is calculated (°F)<br />
e TE = coefficient of thermal expansion<br />
(in./in./°F)<br />
and:<br />
∆MC = M − M o<br />
(M4.4-2)<br />
where:<br />
M o = initial moisture content % (M o ≤ FSP)<br />
M = new moisture content % (M ≤ FSP)<br />
FSP = fiber saturation point<br />
∆T = T − T o<br />
(M4.4-4)<br />
where:<br />
−60°F ≤ T o ≤ 130°F<br />
The coefficient of thermal expansion of ovendry wood<br />
parallel to grain ranges from about 1.7 × 10 -6 to 2.5 × 10 -6<br />
per °F.<br />
Values for e ME and FSP are shown in Table M4.4-2.<br />
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The linear expansion coefficients across the grain<br />
(radial and tangential) are proportional to wood density.<br />
These coefficients are about five to ten times greater than<br />
the parallel-to-the-grain coefficients and are given as:<br />
Radial:<br />
e ⎡ −<br />
⎣18 G 5. 5⎤ ⎦ 10 6 in./in. / ° F (M4.4-5)<br />
TE = ( ) +<br />
Tangential:<br />
( )<br />
e ⎡ −<br />
⎣18 G 10. 2⎤ ⎦ 10 6 in./in. / ° F (M4.4-6)<br />
where:<br />
TE = ( ) +<br />
( )<br />
4<br />
G = tabulated specific gravity for the species.<br />
Table M4.4-2<br />
Species<br />
Coefficient of Moisture Expansion, e ME , and Fiber Saturation<br />
Point, FSP, for Solid <strong>Wood</strong>s<br />
Radial<br />
(in./in./%)<br />
Tangential<br />
(in./in./%)<br />
e ME<br />
Volumetric<br />
(in. 3 /in. 3 /%)<br />
Alaska Cedar 0.0010 0.0021 0.0033 28<br />
Douglas Fir-Larch 0.0018 0.0033 0.0050 28<br />
Englemann Spruce 0.0013 0.0024 0.0037 30<br />
Redwood 0.0012 0.0022 0.0032 22<br />
Red Oak 0.0017 0.0038 0.0063 30<br />
Southern Pine 0.0020 0.0030 0.0047 26<br />
Western Hemlock 0.0015 0.0028 0.0044 28<br />
Yellow Poplar 0.0015 0.0026 0.0041 31<br />
FSP<br />
(%)<br />
M4: SAWN LUMBER<br />
Table M4.4-3 provides the numerical values for e TE<br />
for the most commonly used commercial species or species<br />
groups.<br />
<strong>Wood</strong> that contains moisture reacts to varying temperature<br />
differently than does dry wood. When moist wood<br />
is heated, it tends to expand because of normal thermal<br />
expansion and to shrink because of loss in moisture content.<br />
Unless the wood is very dry initially (perhaps 3%<br />
or 4% MC or less), the shrinkage due to moisture loss<br />
on heating will be greater than the thermal expansion, so<br />
the net dimensional change on heating will be negative.<br />
<strong>Wood</strong> at intermediate moisture levels (about 8% to 20%)<br />
will expand when first heated, then gradually shrink to a<br />
volume smaller than the initial volume, as the wood gradually<br />
loses water while in the heated condition.<br />
Even in the longitudinal (grain) direction, where dimensional<br />
change due to moisture change is very small,<br />
such changes will still predominate over corresponding<br />
dimensional changes due to thermal expansion unless<br />
the wood is very dry initially. For wood at usual moisture<br />
levels, net dimensional changes will generally be negative<br />
after prolonged heating.<br />
Calculation of actual changes in dimensions can be<br />
accomplished by determining the equilibrium moisture<br />
content of wood at the temperature value and relative humidity<br />
of interest. Then the relative dimensional changes<br />
due to temperature change alone and moisture content<br />
change alone are calculated. By combining these two<br />
changes the final dimension of lumber and timber can be<br />
established.<br />
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Table M4.4-3<br />
Coefficient of Thermal Expansion, e TE , for Solid <strong>Wood</strong>s<br />
Durability<br />
e TE<br />
Species Radial (10 -6 in./in./°F) Tangential (10 -6 in./in./°F)<br />
California Redwood 13 18<br />
Douglas Fir-Larch 1 15 19<br />
Douglas Fir, South 14 19<br />
Eastern Spruce 13 18<br />
Hem-Fir 1 13 18<br />
Red Oak 18 22<br />
Southern Pine 15 20<br />
Spruce-Pine-Fir 13 18<br />
Yellow Poplar 14 18<br />
1. Also applies when species name includes the designation “North.”<br />
Designing for durability is a key part of the architectural<br />
and engineering design of the building. This issue is<br />
particularly important in the design of buildings that use<br />
poles and piles. Many design conditions can be detailed<br />
to minimize the potential for decay; for other problem<br />
conditions, preservative-treated wood or naturally durable<br />
species should be specified.<br />
This section does not cover the topic of designing for<br />
durability in detail. There are many excellent texts on the<br />
topic, including AF&PA’s Design of <strong>Wood</strong> Structures for<br />
Permanence, WCD No. 6. Designers are advised to use this<br />
type of information to assist in designing for “difficult”<br />
design areas, such as:<br />
• structures in moist or humid conditions<br />
• where wood comes in contact with concrete<br />
or masonry<br />
• where wood members are supported in steel<br />
hangers or connectors in which condensation<br />
could collect<br />
• anywhere that wood is directly or indirectly<br />
exposed to the elements<br />
• where wood, if it should ever become wet,<br />
could not naturally dry out.<br />
This list is not intended to be all-inclusive – it is<br />
merely an attempt to alert designers to special conditions<br />
that may cause problems when durability is not considered<br />
in the design.<br />
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M4.5 Member Selection Tables<br />
General<br />
<strong>ASD</strong> Capacity Tables<br />
Member selection tables provide <strong>ASD</strong> capacities for<br />
many common designs. Before using the selection tables,<br />
refer to the footnotes to be certain that the tables are appropriate<br />
for the application.<br />
The tables in this section provide design capacity<br />
values for structural lumber and timbers. Moment capacity,<br />
M′, shear capacity, V′, and bending stiffness, EI, are<br />
provided for strong-axis bending. Tension capacity, T′,<br />
and compression capacity, P′, are also tabulated. The applicable<br />
load duration factor, C D , is indicated in each of<br />
the tables.<br />
Footnotes are provided to allow conversion to load<br />
and resistance factor design (<strong>LRFD</strong>) capacities. See NDS<br />
Appendix N for more details on <strong>LRFD</strong>.<br />
For manual calculation, two approaches are possible:<br />
1) review the design equations in the chapter and modify<br />
the tabulated values as necessary; or 2) compute design<br />
capacity directly from the reference design values and<br />
adjustment factors.<br />
To compute the design capacity for a specific condition,<br />
apply the design equations directly. Reference design<br />
values are provided in Chapter 4 of the NDS Supplement<br />
and design adjustment factors are provided in NDS 4.3.<br />
<strong>ASD</strong> capacity tables are provided as follows:<br />
Table M4.5-1 = tension members<br />
Table M4.5-2 = compression members (timbers)<br />
Table M4.5-3 = bending members (lumber)<br />
Table M4.5-4 = bending members (timber)<br />
Refer to the selection table checklist to see whether<br />
your design condition meets the assumptions built into the<br />
tabulated values. Note that the load duration factor, C D ,<br />
is shown at the top of the table. Thus, the member design<br />
capacity can be used directly to select a member that meets<br />
the design requirement.<br />
Examples of the development of the capacity table<br />
values are shown in M4.6.<br />
Compression member tables are based on concentric<br />
axial loads only and pin-pin end conditions. Bending<br />
member tables are based on uniformly distributed loads<br />
on a simple span beam. Values from the compression or<br />
tension member tables and bending member tables cannot<br />
be combined in an interaction equation to determine<br />
combined bending and axial loads. See NDS 3.9 for more<br />
information.<br />
4<br />
M4: SAWN LUMBER<br />
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Table M4.5-1a <strong>ASD</strong> Tension Member Capacity (T'), Structural Lumber 1,2<br />
2-inch nominal thickness Visually Graded Lumber (1.5 inch dry dressed size), C D = 1.0.<br />
4-inch nominal thickness Visually Graded Lumber (3.5 inch dry dressed size), C D = 1.0.<br />
Tension Member Capacity, T' (lbs)<br />
Visually Graded Lumber<br />
Width 2" nominal thickness 4" nominal thickness<br />
Nominal Actual Select Select<br />
Species in. in. Structural No. 1 No. 2 No. 3 Structural No. 1 No. 2<br />
4 3.5 7,870 5,310 4,520 2,550 18,300 12,400 10,500<br />
6 5.5 10,700 7,230 6,160 3,480 25,000 16,800 14,300<br />
Douglas Fir-Larch 8 7.25 13,000 8,000 7,500 4,240 30,400 20,500 17,500<br />
10 9.25 15,260 10,300 8,770 4,960 35,600 24,000 20,400<br />
12 11.25 16,800 11,900 9,700 5,480 39,300 26,500 22,600<br />
4 3.5 7,280 4,920 4,130 2,360 16,900 11,400 9,640<br />
6 5.5 9,900 6,700 5,630 3,210 23,100 15,600 13,100<br />
Hem-Fir 8 7.25 12,000 8,150 6,850 3,910 28,100 19,000 15,900<br />
10 9.25 14,100 9,530 8,010 4,570 32,900 22,200 18,600<br />
12 11.25 15,600 10,500 8,850 5,060 36,400 24,600 20,600<br />
4 3.5 8,400 5,510 4,330 2,490 19,600 12,800 10,100<br />
6 5.5 11,500 7,420 5,980 3,500 26,900 17,300 13,900<br />
Southern Pine 8 7.25 14,100 8,970 7,060 4,350 32,900 20,900 16,400<br />
10 9.25 15,200 10,000 9,280 4,500 35,600 23,400 18,600<br />
12 11.25 17,700 11,300 9,280 5,480 41,300 26,500 21,600<br />
4 3.5 5,510 3,540 3,540 1,960 12,800 8,260 8,260<br />
6 5.5 7,510 4,820 4,280 2,680 17,500 11,200 11,200<br />
Spruce-Pine-Fir 8 7.25 9,130 5,870 5,870 3,260 21,300 13,700 13,700<br />
10 9.25 10,600 6,860 6,860 3,810 24,900 16,000 16,000<br />
12 11.25 11,800 7,590 7,590 4,210 27,500 17,700 17,700<br />
2" nominal thickness 4" nominal thickness<br />
Construction Standard Utility Stud Construction Standard Stud<br />
Douglas Fir-Larch 4 3.5 3,410 1,960 919 2,590 7,960 4,590 6,060<br />
Hem-Fir 4 3.5 3,150 1,700 788 2,310 7,350 3,980 5,390<br />
Southern Pine 4 3.5 3,280 1,830 919 2,490 7,560 4,280 5,810<br />
Spruce-Pine-Fir 4 3.5 2,620 1,440 656 2,020 6,120 3,360 4,710<br />
Table M4.5-1b <strong>ASD</strong> Tension Member Capacity (T'), Structural Lumber 1,2<br />
2-inch nominal thickness MSR Lumber (1.5 inch dry dressed size), C D = 1.0.<br />
Width<br />
Tension Member Capacity, T' (lbs)<br />
Machine Stress Rated Lumber<br />
Nominal Actual 2" nominal thickness<br />
Species in. in. 1200f-1.2E 1350f-1.3E 1450f-1.3E 1650f-1.5E 2100f-1.8E 2250f-1.9E 2400f-2.0E<br />
4 3.5 3,150 3,938 4,200 5,355 8,269 9,188 10,106<br />
6 5.5 4,950 6,188 6,600 8,415 12,994 14,438 15,881<br />
All Species 8 7.25 6,525 8,156 8,700 11,093 17,128 19,031 20,934<br />
10 9.25 8,325 10,406 11,100 14,153 21,853 24,281 26,709<br />
12 11.25 10,125 12,656 13,500 17,213 26,578 29,531 32,484<br />
1. Multiply tabulated <strong>ASD</strong> capacity by 1.728 to obtain <strong>LRFD</strong> capacity (λ = 0.8). See NDS Appendix N for more information.<br />
2. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0.<br />
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Table M4.5-2a <strong>ASD</strong> Column Capacity 1,2,3,4,5 (P', P' x , P' y ), Timbers<br />
6-inch nominal thickness (5.5 inch dry dressed size), C D = 1.0.<br />
Column Capacity (lbs)<br />
Select Structural No. 1 No. 2<br />
6 x 6 6 x 8 6 x 6 6 x 8 6 x 6 6 x 8<br />
6" width 8" width 6" width 8" width 6" width 8" width<br />
Column (=5.5") (=7.5") (=5.5") (=7.5") (=5.5") (=7.5")<br />
Species Length (ft) P' P'x P'y P' P'x P'y P' P'x P'y<br />
Douglas Fir-<br />
Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
2 34,500 47,200 47,000 30,000 41,100 40,900 21,000 28,800 28,700<br />
4 33,400 46,400 45,500 29,200 40,500 39,800 20,500 28,400 28,000<br />
6 31,100 45,000 42,500 27,600 39,500 37,600 19,600 27,800 26,700<br />
8 27,300 42,700 37,300 24,800 37,800 33,800 18,000 26,800 24,500<br />
10 22,300 39,200 30,400 20,900 35,300 28,500 15,700 25,400 21,400<br />
12 17,500 34,600 23,900 16,800 31,800 22,900 13,000 23,400 17,700<br />
14 13,700 29,500 18,700 13,300 27,800 18,200 10,500 20,900 14,300<br />
16 10,900 24,700 14,800 10,700 23,700 14,600 8,500 18,200 11,500<br />
2 29,200 40,000 39,800 25,500 34,900 34,800 17,300 23,600 23,600<br />
4 28,200 39,300 38,500 24,800 34,400 33,800 16,900 23,400 23,000<br />
6 26,200 38,100 35,800 23,300 33,500 31,800 16,100 22,900 22,000<br />
8 22,800 36,000 31,100 20,800 31,900 28,400 14,900 22,100 20,300<br />
10 18,400 32,900 25,100 17,400 29,700 23,700 13,100 21,000 17,800<br />
12 14,300 28,800 19,600 13,800 26,600 18,900 10,900 19,400 14,800<br />
14 11,200 24,300 15,200 10,900 23,000 14,900 8,800 17,400 12,000<br />
16 8,800 20,200 12,000 8,700 19,500 11,900 7,200 15,200 9,800<br />
2 28,500 39,000 38,900 24,800 33,900 33,800 15,800 21,600 21,500<br />
4 27,700 38,500 37,800 24,200 33,500 33,000 15,500 21,400 21,100<br />
6 26,200 37,500 35,700 23,100 32,800 31,500 15,000 21,000 20,400<br />
8 23,500 35,900 32,100 21,200 31,600 28,900 14,100 20,500 19,200<br />
10 19,900 33,500 27,100 18,400 29,900 25,100 12,700 19,700 17,400<br />
12 16,000 30,200 21,800 15,200 27,500 20,700 11,000 18,500 15,000<br />
14 12,700 26,400 17,300 12,300 24,500 16,700 9,200 17,100 12,500<br />
16 10,100 22,400 13,800 9,900 21,300 13,500 7,600 15,300 10,300<br />
2 24,000 32,900 32,700 21,000 28,800 28,700 15,000 20,600 20,500<br />
4 23,400 32,400 31,900 20,500 28,400 28,000 14,700 20,300 20,100<br />
6 22,100 31,600 30,100 19,600 27,800 26,700 14,100 19,900 19,300<br />
8 19,900 30,300 27,100 18,000 26,800 24,500 13,100 19,300 17,900<br />
10 16,800 28,300 23,000 15,700 25,400 21,400 11,600 18,400 15,800<br />
12 13,600 25,600 18,500 13,000 23,400 17,700 9,800 17,100 13,400<br />
14 10,800 22,400 14,700 10,500 20,900 14,300 8,000 15,500 11,000<br />
16 8,600 19,100 11,800 8,500 18,200 11,500 6,500 13,700 8,900<br />
4<br />
M4: SAWN LUMBER<br />
1. P' x values are based on a column continuously braced against weak axis buckling.<br />
2. P' y values are based on a column continuously braced against strong axis buckling.<br />
3. To obtain <strong>LRFD</strong> capacity, see NDS Appendix N.<br />
4. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0.<br />
5. Column capacities are based on concentric axial loads only and pin-pin end conditions (K e = 1.0 per NDS Appendix Table G1).<br />
<strong>American</strong> Forest & paper association
20 M4: SAWN LUMBER<br />
Table M4.5-2b <strong>ASD</strong> Column Capacity (P', P' x , P' y ), Timbers 1,2,3,4,5<br />
8-inch nominal thickness (7.5 inch dry dressed size), C D = 1.0.<br />
Column Capacity (lbs)<br />
Select Structural No. 1 No. 2<br />
8 x 8 8 x 10 8 x 8 8 x 10 8 x 8 8 x 10<br />
8" width 10" width 8" width 10" width 8" width 10" width<br />
Column (=7.5") (=9.5") (=7.5") (=9.5") (=7.5") (=9.5")<br />
Species Length (ft) P' P'x P'y P' P'x P'y P' P'x P'y<br />
Douglas Fir-<br />
Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
2 64,400 81,700 81,500 56,000 71,100 70,900 39,200 49,800 49,700<br />
4 63,300 80,900 80,200 55,200 70,500 70,000 38,800 49,400 49,100<br />
6 61,400 79,500 77,800 53,800 69,400 68,200 37,900 48,800 48,000<br />
8 58,300 77,300 73,800 51,500 67,800 65,300 36,600 47,800 46,300<br />
10 53,500 74,000 67,800 48,100 65,400 60,900 34,600 46,500 43,800<br />
12 47,200 69,600 59,800 43,400 62,200 55,000 31,900 44,600 40,400<br />
14 40,200 63,800 50,900 37,900 58,000 48,000 28,500 42,100 36,100<br />
16 33,600 57,000 42,600 32,300 52,800 40,900 24,800 39,100 31,400<br />
2 54,600 69,200 69,100 47,600 60,400 60,300 32,200 40,900 40,800<br />
4 53,600 68,500 67,900 46,900 59,900 59,400 31,900 40,600 40,400<br />
6 51,900 67,300 65,800 45,600 58,900 57,800 31,200 40,100 39,500<br />
8 49,100 65,300 62,200 43,600 57,500 55,200 30,100 39,300 38,200<br />
10 44,800 62,400 56,800 40,400 55,300 51,200 28,600 38,300 36,200<br />
12 39,200 58,400 49,700 36,200 52,400 45,900 26,400 36,800 33,500<br />
14 33,200 53,200 42,000 31,400 48,600 39,700 23,700 34,900 30,100<br />
16 27,600 47,300 34,900 26,500 44,000 33,600 20,800 32,500 26,300<br />
2 53,200 67,500 67,400 46,200 58,600 58,600 29,400 37,300 37,300<br />
4 52,500 66,900 66,500 45,700 58,200 57,900 29,200 37,100 36,900<br />
6 51,100 65,900 64,700 44,700 57,500 56,600 28,700 36,800 36,300<br />
8 48,900 64,400 62,000 43,100 56,300 54,600 27,900 36,200 35,400<br />
10 45,700 62,200 57,800 40,700 54,700 51,600 26,800 35,400 34,000<br />
12 41,200 59,100 52,200 37,500 52,500 47,500 25,300 34,400 32,000<br />
14 35,900 55,000 45,500 33,400 49,600 42,400 23,300 33,000 29,500<br />
16 30,600 50,200 38,800 29,100 46,000 36,800 20,900 31,300 26,500<br />
2 44,800 56,800 56,800 39,200 49,800 49,700 28,000 35,500 35,500<br />
4 44,200 56,400 56,000 38,800 49,400 49,100 27,700 35,300 35,100<br />
6 43,100 55,500 54,600 37,900 48,800 48,000 27,200 34,900 34,400<br />
8 41,300 54,300 52,300 36,600 47,800 46,300 26,300 34,300 33,400<br />
10 38,600 52,400 48,900 34,600 46,500 43,800 25,100 33,400 31,800<br />
12 34,900 49,900 44,200 31,900 44,600 40,400 23,400 32,300 29,600<br />
14 30,500 46,500 38,600 28,500 42,100 36,100 21,200 30,700 26,800<br />
16 26,000 42,500 33,000 24,800 39,100 31,400 18,700 28,800 23,700<br />
1. P' x values are based on a column continuously braced against weak axis buckling.<br />
2. P' y values are based on a column continuously braced against strong axis buckling.<br />
3. To obtain <strong>LRFD</strong> capacity, see NDS Appendix N.<br />
4. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0.<br />
5. Column capacities are based on concentric axial loads only and pin-pin end conditions (K e = 1.0 per NDS Appendix Table G1).<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
21<br />
Table M4.5-2c <strong>ASD</strong> Column Capacity (P', P' x , P' y ), Timbers 1,2,3,4,5<br />
10-inch nominal thickness (9.5 inch dry dressed size), C D = 1.0.<br />
Column Capacity (lbs)<br />
Select Structural No. 1 No. 2<br />
10 x 10 10 x 12 10 x 10 10 x 12 10 x 10 10 x 12<br />
10" width 12 width 10" width 12 width 10" width 12 width<br />
Column (=9.5") (=11.5") (=9.5") (=11.5") (=9.5") (=11.5")<br />
Species Length (ft) P' P'x P'y P' P'x P'y P' P'x P'y<br />
Douglas Fir-<br />
Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
2 103,500 125,400 125,200 90,000 109,000 109,000 63,000 76,400 76,300<br />
4 102,500 124,600 124,000 89,300 108,400 108,000 62,600 76,000 75,700<br />
6 100,700 123,100 121,900 87,900 107,400 106,400 61,800 75,300 74,800<br />
8 97,900 121,000 118,500 85,900 105,800 103,900 60,600 74,400 73,300<br />
10 93,800 117,900 113,500 82,900 103,500 100,300 58,800 73,100 71,200<br />
12 88,100 113,800 106,700 78,800 100,500 95,400 56,500 71,300 68,400<br />
14 80,800 108,300 97,800 73,400 96,600 88,900 53,400 69,100 64,600<br />
16 72,200 101,500 87,500 66,900 91,600 81,000 49,500 66,200 59,900<br />
2 87,700 106,300 106,200 76,500 92,700 92,600 51,800 62,700 62,700<br />
4 86,800 105,600 105,100 75,800 92,100 91,800 51,400 62,400 62,200<br />
6 85,200 104,300 103,100 74,600 91,200 90,300 50,800 61,900 61,500<br />
8 82,700 102,400 100,100 72,800 89,700 88,100 49,800 61,200 60,300<br />
10 79,000 99,600 95,700 70,100 87,700 84,800 48,500 60,100 58,700<br />
12 73,900 95,900 89,500 66,400 85,000 80,400 46,600 58,800 56,400<br />
14 67,400 91,000 81,600 61,500 81,500 74,500 44,200 57,000 53,500<br />
16 59,900 84,900 72,500 55,700 77,000 67,500 41,100 54,700 49,800<br />
2 85,500 103,600 103,500 74,300 90,000 89,900 47,300 57,300 57,200<br />
4 84,800 103,000 102,600 73,700 89,500 89,300 47,000 57,100 56,900<br />
6 83,500 102,000 101,100 72,800 88,800 88,100 46,600 56,700 56,400<br />
8 81,600 100,500 98,700 71,400 87,700 86,400 45,800 56,100 55,500<br />
10 78,700 98,300 95,300 69,300 86,100 83,900 44,900 55,400 54,300<br />
12 74,800 95,500 90,600 66,500 84,000 80,500 43,500 54,400 52,700<br />
14 69,700 91,700 84,400 62,800 81,300 76,000 41,800 53,100 50,600<br />
16 63,500 87,000 76,900 58,200 77,900 70,500 39,600 51,500 47,900<br />
2 72,000 87,200 87,200 63,000 76,400 76,300 45,000 54,500 54,500<br />
4 71,400 86,800 86,400 62,600 76,000 75,700 44,700 54,300 54,200<br />
6 70,400 85,900 85,200 61,800 75,300 74,800 44,200 53,900 53,500<br />
8 68,700 84,600 83,200 60,600 74,400 73,300 43,400 53,300 52,600<br />
10 66,400 82,900 80,400 58,800 73,100 71,200 42,400 52,400 51,300<br />
12 63,200 80,500 76,500 56,500 71,300 68,400 40,900 51,300 49,500<br />
14 59,000 77,400 71,400 53,400 69,100 64,600 38,900 49,900 47,100<br />
16 53,800 73,500 65,200 49,500 66,200 59,900 36,500 48,100 44,100<br />
4<br />
M4: SAWN LUMBER<br />
1. P' x values are based on a column continuously braced against weak axis buckling.<br />
2. P' y values are based on a column continuously braced against strong axis buckling.<br />
3 . To obtain <strong>LRFD</strong> capacity, see NDS Appendix N.<br />
4. Tabulated values apply to members in a dry service condition, C M =1.0; normal temperature range, C t =1.0; and unincised members, C i =1.0.<br />
5. Column capacities are based on concentric axial loads only and pin-pin end conditions (K e = 1.0 per NDS Appendix Table G1).<br />
<strong>American</strong> Forest & paper association
22 M4: SAWN LUMBER<br />
Table M4.5-3a <strong>ASD</strong> Bending Member Capacity (M', C r M', V', and EI), Structural<br />
Lumber 1,2<br />
2-inch nominal thickness (1.5 inch dry dressed size), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' Cr M' V' x 10 6 EI M' Cr M' V' x 10 6 EI<br />
Nominal Actual (Single) (Repetitive) (Repetitive)<br />
Species (in.) (in.) lb-in. lb-in. lbs lb-in. 2 lb-in. lb-in. lbs lb-in. 2<br />
2 x 4 1.5 x 3.5 6,890 7,920 630 10 4,130 4,750 630 9<br />
Douglas Fir-Larch<br />
2 x 6 1.5 x 5.5 14,700 17,000 990 40 8,850 10,200 990 33<br />
2 x 8 1.5 x 7.25 23,700 27,200 1,310 91 14,200 16,300 1,310 76<br />
2 x 10 1.5 x 9.25 35,300 40,600 1,670 188 21,200 24,400 1,670 158<br />
2 x 12 1.5 x 11.25 47,500 54,600 2,030 338 28,500 32,700 2,030 285<br />
2 x 4 1.5 x 3.5 6,430 7,400 525 9 3,900 4,490 525 7<br />
2 x 6 1.5 x 5.5 13,800 15,900 825 33 8,360 9,610 825 27<br />
Hem-Fir<br />
2 x 8 1.5 x 7.25 22,100 25,400 1,090 76 13,400 15,400 1,090 62<br />
2 x 10 1.5 x 9.25 32,900 37,900 1,390 158 20,000 23,000 1,390 129<br />
2 x 12 1.5 x 11.25 44,300 50,900 1,690 285 26,900 30,900 1,690 231<br />
2 x 4 1.5 x 3.5 8,730 10,000 613 10 4,590 5,280 613 9<br />
2 x 6 1.5 x 5.5 19,300 22,200 963 37 9,450 10,900 963 33<br />
Southern Pine 2 x 8 1.5 x 7.25 30,200 34,800 1,270 86 15,800 18,100 1,270 76<br />
2 x 10 1.5 x 9.25 43,900 50,400 1,620 178 22,500 25,800 1,620 158<br />
2 x 12 1.5 x 11.25 60,100 69,100 1,970 320 30,800 35,500 1,970 285<br />
2 x 4 1.5 x 3.5 5,740 6,600 473 8 4,020 4,620 473 8<br />
2 x 6 1.5 x 5.5 12,300 14,100 743 31 8,600 9,890 743 29<br />
Spruce-Pine-Fir 2 x 8 1.5 x 7.25 19,700 22,700 979 71 13,800 15,900 979 67<br />
2 x 10 1.5 x 9.25 29,400 33,800 1,250 148 20,600 23,700 1,250 139<br />
2 x 12 1.5 x 11.25 39,600 45,500 1,520 267 27,700 31,800 1,520 249<br />
Table M4.5-3b <strong>ASD</strong> Bending Member Capacity (M', C r M', V', and EI), Structural<br />
Lumber 1,2<br />
4-inch nominal thickness (3.5 inch dry dressed size), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' Cr M' V' x 10 6 EI M' Cr M' V' x 10 6 EI<br />
Nominal Actual (Single) (Repetitive) (Repetitive)<br />
Species (in.) (in.) lb-in. lb-in. lbs lb-in. 2 lb-in. lb-in. lbs lb-in. 2<br />
4 x 4 3.5 x 3.5 16,100 18,500 1,470 24 9,650 11,100 1,470 20<br />
Douglas Fir-Larch<br />
4 x 6 3.5 x 5.5 34,400 39,600 2,310 92 20,600 23,700 2,310 78<br />
4 x 8 3.5 x 7.25 59,800 68,800 3,050 211 35,900 41,300 3,050 178<br />
4 x 10 3.5 x 9.25 89,800 103,000 3,890 439 53,900 62,000 3,890 370<br />
4 x 12 3.5 x 11.25 122,000 140,000 4,730 789 73,100 84,100 4,730 664<br />
4 x 4 3.5 x 3.5 15,000 17,300 1,230 20 9,110 10,500 1,230 16<br />
4 x 6 3.5 x 5.5 32,100 36,900 1,930 78 19,500 22,400 1,930 63<br />
Hem-Fir<br />
4 x 8 3.5 x 7.25 55,800 64,200 2,540 178 33,900 39,000 2,540 144<br />
4 x 10 3.5 x 9.25 83,900 96,400 3,240 369 50,900 58,500 3,240 300<br />
4 x 12 3.5 x 11.25 114,000 131,000 3,940 664 69,000 79,400 3,940 540<br />
4 x 4 3.5 x 3.5 20,400 23,400 1,430 23 10,700 12,300 1,430 20<br />
4 x 6 3.5 x 5.5 45,000 51,700 2,250 87 22,100 25,400 2,250 78<br />
Southern Pine 4 x 8 3.5 x 7.25 77,600 89,200 2,960 200 40,500 46,600 2,960 178<br />
4 x 10 3.5 x 9.25 113,000 129,000 3,780 416 57,600 66,300 3,780 369<br />
4 x 12 3.5 x 11.25 154,000 177,000 4,590 748 79,200 91,100 4,590 664<br />
4 x 4 3.5 x 3.5 13,400 15,400 1,100 19 9,380 10,800 1,100 18<br />
4 x 6 3.5 x 5.5 28,700 33,000 1,730 73 20,100 23,100 1,730 68<br />
Spruce-Pine-Fir 4 x 8 3.5 x 7.25 49,800 57,300 2,280 167 34,900 40,100 2,280 156<br />
4 x 10 3.5 x 9.25 74,900 86,100 2,910 346 52,400 60,300 2,910 323<br />
4 x 12 3.5 x 11.25 102,000 117,000 3,540 623 71,100 81,700 3,540 581<br />
1. Multiply tabulated M', C r M', and V' capacity by 1.728 to obtain <strong>LRFD</strong> capacity (λ = 0.8). Tabulated EI is applicable for both <strong>ASD</strong> and <strong>LRFD</strong>. See NDS Appendix<br />
N for more information.<br />
2. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0; members braced<br />
against buckling, C L = 1.0.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
23<br />
Table M4.5-4a <strong>ASD</strong> Bending Member Capacity (M', V', and EI), Timbers 1,2<br />
6-inch nominal thickness (5.5 inch dry dressed size), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' V' x 10 6 EI M' V' x 10 6 EI<br />
Nominal Actual (Single)<br />
Species (in.) (in.) lb-in. lbs lb-in. 2 lb-in. lbs lb-in. 2<br />
Douglas Fir-Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
6 x 6 5.5 x 5.5 41,600 3,430 122 20,800 3,430 99<br />
6 x 8 5.5 x 7.5 77,300 4,680 309 38,700 4,680 251<br />
6 x 10 5.5 x 9.5 132,000 5,920 629 72,400 5,920 511<br />
6 x 12 5.5 x 11.5 194,000 7,170 1,120 106,000 7,170 906<br />
6 x 14 5.5 x 13.5 264,000 8,420 1,800 144,000 8,420 1,470<br />
6 x 16 5.5 x 15.5 342,000 9,660 2,730 187,000 9,660 2,220<br />
6 x 6 5.5 x 5.5 33,300 2,820 99 15,900 2,820 84<br />
6 x 8 5.5 x 7.5 61,900 3,850 251 29,600 3,850 213<br />
6 x 10 5.5 x 9.5 10,800 4,880 511 55,800 4,880 432<br />
6 x 12 5.5 x 11.5 15,800 5,900 906 81,800 5,900 767<br />
6 x 14 5.5 x 13.5 214,000 6,930 1,470 111,000 6,930 1,240<br />
6 x 16 5.5 x 15.5 278,000 7,960 2,220 144,000 7,960 1,880<br />
6 x 6 5.5 x 5.5 41,600 3,330 114 23,600 3,330 92<br />
6 x 8 5.5 x 7.5 77,300 4,540 290 43,800 4,540 232<br />
6 x 10 5.5 x 9.5 124,000 5,750 589 70,300 5,750 472<br />
6 x 6 5.5 x 5.5 29,100 2,520 99 13,900 2,520 76<br />
6 x 8 5.5 x 7.5 54,100 3,440 251 25,800 3,440 193<br />
6 x 10 5.5 x 9.5 91,000 4,350 511 49,600 4,350 393<br />
4<br />
M4: SAWN LUMBER<br />
Table M4.5-4b <strong>ASD</strong> Bending Member Capacity (M', V', and EI), Timbers 1,2<br />
8-inch nominal thickness (7.5 inch dry dressed size), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' V' x 10 6 EI M' V' x 10 6 EI<br />
Nominal Actual (Single)<br />
Species (in.) (in.) lb-in. lbs lb-in. 2 lb-in. lbs lb-in. 2<br />
Douglas Fir-Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
8 x 8 7.5 x 7.5 105,000 6,380 422 52,700 6,380 343<br />
8 x 10 7.5 x 9.5 169,000 8,080 857 84,600 8,080 697<br />
8 x 12 7.5 x 11.5 265,000 9,780 1,520 145,000 9,780 1,240<br />
8 x 14 7.5 x 13.5 360,000 11,500 2,460 197,000 11,500 2,000<br />
8 x 16 7.5 x 15.5 467,000 13,200 3,720 255,000 13,200 3,030<br />
8 x 8 7.5 x 7.5 84,400 5,250 343 40,400 5,250 290<br />
8 x 10 7.5 x 9.5 135,000 6,650 697 64,900 6,650 589<br />
8 x 12 7.5 x 11.5 215,000 8,050 1,240 112,000 8,050 1,050<br />
8 x 14 7.5 x 13.5 292,000 9,450 2,000 152,000 9,450 1,690<br />
8 x 16 7.5 x 15.5 379,000 10,900 3,030 197,000 10,900 2,560<br />
8 x 8 7.5 x 7.5 105,000 6,190 396 59,800 6,190 316<br />
8 x 10 7.5 x 9.5 169,000 7,840 804 95,900 7,840 643<br />
8 x 8 7.5 x 7.5 73,800 4,690 343 35,200 4,690 264<br />
8 x 10 7.5 x 9.5 118,000 5,940 697 56,400 5,940 536<br />
1. Multiply tabulated M' and V' capacity by 1.728 to obtain <strong>LRFD</strong> capacity (λ = 0.8). Tabulated EI is applicable for both <strong>ASD</strong> and <strong>LRFD</strong>. See NDS Appendix N for<br />
more information.<br />
2. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0; members braced<br />
against buckling, C L = 1.0.<br />
<strong>American</strong> Forest & paper association
24 M4: SAWN LUMBER<br />
Table M4.5-4c <strong>ASD</strong> Bending Member Capacity (M', V', and EI), Timbers 1,2<br />
10-inch nominal thickness (9.5 inch dry dressed size), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' V' x 10 6 EI M' V' x 10 6 EI<br />
Nominal Actual (Single)<br />
Species (in.) (in.) lb-in. lbs lb-in. 2 lb-in. lbs lb-in. 2<br />
Douglas Fir-Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
10 x 10 9.5 x 9.5 214,000 10,200 1,090 107,000 10,200 882<br />
10 x 12 9.5 x 11.5 314,000 12,400 1,930 157,000 12,400 1,570<br />
10 x 14 9.5 x 13.5 456,000 14,500 3,120 249,000 14,500 2,530<br />
10 x 16 9.5 x 15.5 592,000 16,700 4,720 324,000 16,700 3,830<br />
10 x 18 9.5 x 17.5 744,000 18,800 6,790 407,000 18,800 5,520<br />
10 x 20 9.5 x 19.5 913,000 21,000 9,390 499,000 21,000 7,630<br />
10 x 10 9.5 x 9.5 171,000 8,420 882 82,200 8,420 747<br />
10 x 12 9.5 x 11.5 251,000 10,200 1,570 120,000 10,200 1,320<br />
10 x 14 9.5 x 13.5 370,000 12,000 2,530 192,000 12,000 2,140<br />
10 x 16 9.5 x 15.5 418,000 13,700 3,830 250,000 13,700 3,240<br />
10 x 18 9.5 x 17.5 604,000 15,500 5,520 314,000 15,500 4,670<br />
10 x 20 9.5 x 19.5 742,000 17,300 7,630 385,000 17,300 6,460<br />
10 x 10 9.5 x 9.5 214,000 9,930 1,020 121,000 9,930 815<br />
10 x 12 9.5 x 11.5 314,000 12,000 1,810 178,000 12,000 1,440<br />
10 x 14 9.5 x 13.5 427,000 14,100 2,920 242,000 14,100 2,340<br />
10 x 10 9.5 x 9.5 150,000 7,520 882 71,000 7,520 679<br />
10 x 12 9.5 x 11.5 220,000 9,100 1,570 105,000 9,100 1,200<br />
10 x 14 9.5 x 13.5 313,000 10,700 2,530 171,000 10,700 1,950<br />
Table M4.5-4d <strong>ASD</strong> Bending Member Capacity (M', V', and EI), Timbers 1,2<br />
nominal dimensions > 10 inch (actual = nominal – 1/2 inch), C D = 1.0, C L = 1.0.<br />
Select Structural No. 2<br />
Size (b x d) M' V' x 10 6 EI M' V' x 10 6 EI<br />
Nominal Actual (Single)<br />
Species (in.) (in.) lb-in. lbs lb-in. 2 lb-in. lbs lb-in. 2<br />
Douglas Fir-Larch<br />
Hem-Fir<br />
Southern Pine<br />
Spruce-Pine-Fir<br />
12 x 12 11.5 x 11.5 380,000 15,000 2,330 190,000 15,000 1,890<br />
14 x 14 13.5 x 13.5 607,000 20,700 4,430 304,000 20,700 3,600<br />
16 x 16 15.5 x 15.5 905,000 27,200 7,700 452,000 27,200 6,250<br />
18 x 18 17.5 x 17.5 1,280,000 34,700 12,500 642,000 34,700 10,200<br />
20 x 20 19.5 x 19.5 1,760,000 43,100 19,300 878,000 43,100 15,700<br />
12 x 12 11.5 x 11.5 304,000 12,300 1,890 146,000 12,300 1,600<br />
14 x 14 13.5 x 13.5 486,000 17,000 3,600 233,000 17,000 3,040<br />
16 x 16 15.5 x 15.5 724,000 22,400 6,250 347,000 22,400 5,290<br />
18 x 18 17.5 x 17.5 1,030,000 28,600 10,200 493,000 28,600 8,600<br />
20 x 20 19.5 x 19.5 1,410,000 35,500 15,700 673,000 35,500 13,300<br />
12 x 12 11.5 x 11.5 380,000 14,500 2,190 215,000 14,500 1,750<br />
14 x 14 13.5 x 13.5 607,000 20,000 4,150 344,000 20,000 3,320<br />
12 x 12 11.5 x 11.5 266,000 11,000 1,890 127,000 11,000 1,460<br />
14 x 14 13.5 x 13.5 425,000 15,200 3,600 202,000 15,200 2,770<br />
1 . Multiply tabulated M' and V' capacity by 1.728 to obtain <strong>LRFD</strong> capacity (λ = 0.8). Tabulated EI is applicable for both <strong>ASD</strong> and <strong>LRFD</strong>. See NDS Appendix N for<br />
more information.<br />
2. Tabulated values apply to members in a dry service condition, C M = 1.0; normal temperature range, C t = 1.0; and unincised members, C i = 1.0; members braced<br />
against buckling, C L = 1.0.<br />
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25<br />
M4.6 Examples of Capacity Table Development<br />
Tension Capacity Tables<br />
and:<br />
F * c = reference compression design value<br />
The general design equation for tension members is:<br />
multiplied by all applicable adjustment<br />
T ′ ≥ T<br />
factors except C p<br />
A = area<br />
where:<br />
C<br />
T = tension force due to design loads<br />
P = column stability factor<br />
F<br />
T′ = allowable tension capacity<br />
c ′ = adjusted parallel-to-grain compression<br />
design value<br />
Example M4.6-1: Application – tension<br />
E min ′ = adjusted modulus of elasticity for column<br />
member<br />
stability calculations<br />
Species: Hem-Fir<br />
c = 0.8 for solid sawn members<br />
Size: 2 x 6 (1.5 in. by 5.5 in.)<br />
Grade: 1650f-1.5E MSR<br />
Example M4.6-2: Application – simple column<br />
F t : 1,020 psi<br />
Species: Douglas Fir-Larch<br />
A: 8.25 in. 2<br />
Size: 6 x 8 (5.5 in. by 7.5 in.) by 12 ft.<br />
Grade: No. 1 (dry) Posts and Timbers<br />
Tension Capacity<br />
F * c: 1,000 psi<br />
T′ = F′<br />
t<br />
A<br />
E min : 580,000 psi<br />
= ( 1,020)( 8.25)<br />
A: 41.25 in 2<br />
= 8, 415 lbs<br />
Column Capacity – x-axis<br />
Column Capacity Tables<br />
0.822E<br />
′<br />
min<br />
FcE =<br />
2<br />
( <br />
e<br />
/ dx<br />
)<br />
The general design equation is:<br />
0.822( 580,000)<br />
P′ ≥ P<br />
=<br />
( 144/7.5) 2<br />
where:<br />
= 1, 293 psi<br />
P = compressive force due to design loads<br />
P′ = allowable compression capacity<br />
1+ ( 1, 293/1,000)<br />
Axial Capacity<br />
C<br />
Px<br />
=<br />
2( 0.8)<br />
P′ = C p AF * c<br />
2<br />
⎛1+ ( 1, 293/1,000)<br />
⎞ 1, 293/1,000<br />
where:<br />
−<br />
⎜<br />
2( 0.8)<br />
⎟<br />
−<br />
⎝<br />
⎠ 0.8<br />
* *<br />
1+ ( F ) ( ) 2<br />
*<br />
cE<br />
/ F ⎛<br />
c<br />
1+<br />
F<br />
cE<br />
/ F ⎞<br />
= 0.772<br />
c F<br />
cE<br />
/ Fc<br />
C<br />
P<br />
= − −<br />
2c ⎜ 2c ⎟ c<br />
⎝<br />
⎠<br />
P′<br />
x<br />
= ( 0.772)( 41.25)( 1,000)<br />
0.822E′<br />
= 31,845 lb.<br />
FcE =<br />
2<br />
/ d<br />
( )<br />
e<br />
4<br />
M4: SAWN LUMBER<br />
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26 M4: SAWN LUMBER<br />
Column Capacity – y-axis<br />
F<br />
0.822E<br />
=<br />
min<br />
cE 2<br />
( <br />
e<br />
/ d<br />
y)<br />
( )<br />
( 144/5.5) 2<br />
0.822 580,000<br />
=<br />
= 696 psi<br />
′<br />
( )<br />
2( 0.8)<br />
1+ 696/1,000<br />
C =<br />
x<br />
Py<br />
P′ =<br />
( )<br />
( )<br />
⎛1+ 696/1,000 ⎞ 696/1,000<br />
−<br />
⎜<br />
−<br />
2 0.8 ⎟<br />
⎝<br />
⎠ 0.8<br />
= 0.556<br />
( 0.556)( 41.25)( 1,000)<br />
= 22,952 lb<br />
Bending Member Capacity Tables<br />
where:<br />
where:<br />
The general design equation for flexural bending is:<br />
M′ ≥ M<br />
M = moment due to design loads<br />
M′ = allowable moment capacity<br />
The general design equation for flexural shear is:<br />
V′ ≥ V<br />
V = shear force due to design loads<br />
V′ = allowable shear capacity<br />
2<br />
Example M4.6-3: Application – structural<br />
lumber<br />
Species: Douglas Fir-Larch<br />
Size: 2 x 6 (1.5 in. by 5.5 in.)<br />
Grade: No. 2<br />
C F : 1.3 (size factor)<br />
C r : 1.15 (repetitive member factor)<br />
F b : 900 psi<br />
F v : 180 psi<br />
E: 1,600,000 psi<br />
A: 8.25 in. 2<br />
S: 7.56 in. 3<br />
I: 20.80 in. 4<br />
Moment Capacity<br />
C M ′ = F C C S<br />
r b F r<br />
Shear Capacity<br />
= ( 900)( 1.3)( 1.15)( 7.56)<br />
= 10,172 lb -in.<br />
2<br />
V ′ = F′<br />
v<br />
A ⎛ ⎜ ⎞<br />
⎟<br />
⎝ 3 ⎠<br />
⎛ 2 ⎞<br />
= ( 180)( 8.25)<br />
⎜ ⎟<br />
⎝ 3 ⎠<br />
= 990 lb<br />
Flexural Stiffness<br />
EI = (1,600,000)(20.80) = 33 × 10 6 lb - in. 2<br />
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27<br />
M5: STRUCTURAL<br />
GLUED<br />
LAMINATED<br />
TIMBER<br />
5<br />
M5.1 General 28<br />
M5.2 Reference Design Values 30<br />
M5.3 Adjustment of Reference<br />
Design Values 31<br />
M5.4 Special Design Considerations 32<br />
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28 M5: structural glued laminated timber<br />
M5.1 General<br />
Products Description<br />
Structural glued laminated timber (glulam) is a structural<br />
member glued up from suitably selected and prepared<br />
pieces of wood either in a straight or curved form with the<br />
grain of all of the pieces parallel to the longitudinal axis<br />
of the member. The reference design values given in the<br />
NDS Supplement are applicable only to structural glued<br />
laminated timber members produced in accordance with<br />
<strong>American</strong> National Standard for <strong>Wood</strong> Products — Structural<br />
Glued Laminated Timber, ANSI/AITC A190.1.<br />
Structural glued laminated timber members are produced<br />
in laminating plants by gluing together dry lumber,<br />
normally of 2-inch or 1-inch nominal thickness, under<br />
controlled temperature and pressure conditions. Members<br />
with a wide variety of sizes, profiles, and lengths can<br />
be produced having superior characteristics of strength,<br />
serviceability, and appearance. Structural glued laminated<br />
timber beams are manufactured with the strongest<br />
laminations on the bottom and top of the beam, where the<br />
greatest tension and compression stresses occur in bending.<br />
This allows a more efficient use of the lumber resource<br />
by placing higher grade lumber in zones that have higher<br />
stresses and lumber with less structural quality in lower<br />
stressed zones.<br />
Structural glued laminated timber members are manufactured<br />
from several softwood species, primarily Douglas<br />
fir-larch, southern pine, hem-fir, spruce-pine-fir, eastern<br />
spruce, western woods, Alaska cedar, Durango pine, and<br />
California redwood. In addition, several hardwood species,<br />
including red oak, red maple, and yellow poplar, are also<br />
used. Standard structural glued laminated timber sizes<br />
are given in the NDS Supplement. Any length, up to the<br />
maximum length permitted by transportation and handling<br />
restrictions, is available.<br />
A structural glued laminated timber member can be<br />
manufactured using a single grade or multiple grades of<br />
lumber, depending on intended use. In addition, a mixedspecies<br />
structural glued laminated timber member is also<br />
possible. When the member is intended to be primarily<br />
loaded either axially or in bending with the loads acting<br />
parallel to the wide faces of the laminations, a single<br />
grade combination is recommended. On the other hand,<br />
a multiple grade combination provides better cost-effectiveness<br />
when the member is primarily loaded in bending<br />
due to loads applied perpendicular to the wide faces of<br />
the laminations.<br />
On a multiple grade combination, a structural glued<br />
laminated timber member can be produced as either a<br />
balanced or unbalanced combination, depending on the<br />
geometrical arrangement of the laminations about the<br />
mid-depth of the member. As shown in Figure M5.1-1, a<br />
balanced combination is symmetrical about the mid-depth,<br />
so both faces have the same reference bending design<br />
value. Unbalanced combinations are asymmetrical and<br />
when used as a beam, the face with a lower allowable<br />
bending stress is stamped as TOP. The balanced combination<br />
is intended for use in continuous or cantilevered over<br />
supports to provide equal capacity in both positive and<br />
negative bending. Whereas the unbalanced combination<br />
is primarily for use in simple span applications, they can<br />
also be used for short cantilever applications (cantilever<br />
less than 20% of the back span) or for continuous span<br />
applications when the design is controlled by shear or<br />
deflection.<br />
Figure M5.1-1<br />
No. 2D<br />
Unbalanced and<br />
Balanced Layup<br />
Combinations<br />
Tension Lam<br />
No. 2 No. 1<br />
No. 2 No. 2<br />
No. 3 No. 3<br />
No. 3 No. 3<br />
No. 3 No. 3<br />
No. 2 No. 2<br />
No. 1 No. 1<br />
Tension Lam<br />
Unbalanced<br />
Tension Lam<br />
Balanced<br />
Structural glued laminated timber members can be<br />
used as primary or secondary load-carrying components<br />
in structures. Table M5.1-1 lists economical spans for<br />
selected timber framing systems using structural glued<br />
laminated timber members in buildings. Other common<br />
uses of structural glued laminated timber members are<br />
for utility structures, pedestrian bridges, highway bridges,<br />
railroad bridges, marine structures, noise barriers, and<br />
towers. Table M5.1-1 may be used for preliminary design<br />
purposes to determine the economical span ranges for the<br />
selected framing systems. However, all systems require a<br />
more extensive analysis for final design.<br />
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29<br />
Table M5.1-1<br />
Economical Spans<br />
for Structural Glued<br />
Laminated Timber<br />
Framing Systems<br />
Type of Framing System<br />
Economical<br />
Spans (ft)<br />
ROOF<br />
Simple Span Beams<br />
Straight or slightly cambered 10 to 100<br />
Tapered, double tapered-pitched, or 25 to 105<br />
curved<br />
Cantilevered Beams (Main span) up to 90<br />
Continuous Beams (Interior spans) 10 to 50<br />
Girders 40 to 100<br />
Three-Hinged Arches<br />
Gothic 40 to 100<br />
Tudor 40 to 140<br />
A-Frame 20 to 100<br />
Three-centered, Parabolic, or Radial 40 to 250<br />
Two-Hinged Arches<br />
Radial or Parabolic 50 to 200<br />
Trusses (Four or more ply chords)<br />
Flat or parallel chord 50 to 150<br />
Triangular or pitched 50 to 150<br />
Bowstring (Continuous chord) 50 to 200<br />
Trusses (Two or three ply chords)<br />
Flat or parallel chord 20 to 75<br />
Triangular or pitched 20 to 75<br />
Tied arches 50 to 200<br />
Dome structures 200 to 500+<br />
FLOOR<br />
Simple Span Beams 10 to 40<br />
Continuous Beams (Individual spans) 10 to 40<br />
Headers<br />
Windows and Doors < 10<br />
Garage Doors 9 to 18<br />
Appearance Classifications<br />
Structural glued laminated timber members are<br />
typically produced in four appearance classifications:<br />
Premium, Architectural, Industrial, and Framing. Premium<br />
and Architectural beams are higher in appearance qualities<br />
and are surfaced for a smooth finish ready for staining or<br />
painting. Industrial classification beams are normally used<br />
in concealed applications or in construction where appearance<br />
is not important. Framing classification beams are<br />
typically used for headers and other concealed applications<br />
in residential construction. Design values for structural<br />
glued laminated timber members are independent of the<br />
appearance classifications.<br />
For more information and detailed descriptions of these<br />
appearance classifications and their typical uses, refer to<br />
APA EWS Technical Note Y110 or AITC Standard 110.<br />
Availability<br />
Structural glued laminated timber members are available<br />
in both custom and stock sizes. Custom beams are<br />
manufactured to the specifications of a specific project,<br />
while stock beams are made in common dimensions,<br />
shipped to distribution yards, and cut to length when the<br />
beam is ordered. Stock beams are available in virtually<br />
every major metropolitan area. Although structural glued<br />
laminated timber members can be custom fabricated to<br />
provide a nearly infinite variety of forms and sizes, the<br />
best economy is generally realized by using standard-size<br />
members as noted in the NDS Supplement. When in doubt,<br />
the designer is advised to check with the structural glued<br />
laminated timber supplier or manufacturer concerning the<br />
availability of a specific size prior to specification.<br />
5<br />
M5: STRUCTURAL GLUED LAMINATED TIMBER<br />
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30 M5: structural glued laminated timber<br />
M5.2 Reference Design Values<br />
Reference design values of structural glued laminated<br />
timber are affected by the layup of members composed of<br />
various grades of lumber as well as the direction of applied<br />
bending forces. As a result, different design values<br />
are assigned for structural glued laminated timber used<br />
primarily in bending (NDS Supplement Table 5A) and<br />
primarily in axial loading (NDS Supplement Table 5B).<br />
The reference design values are used in conjunction with<br />
the dimensions provided in Table 1C (western species) and<br />
Table 1D (southern pine) of the NDS Supplement, but are<br />
applicable to any size of structural glued laminated timber<br />
when the appropriate modification factors discussed in<br />
M5.3 are applied.<br />
Reference design values are given in NDS Supplement<br />
Table 5A for bending about the X-X axis (see Figure<br />
M5.2‐1). Although permitted, axial loading or bending<br />
about the Y-Y axis (also see Figure M5.2-1) is not efficient<br />
in using the structural glued laminated timber combinations<br />
given in NDS Supplement Table 5A. In such cases, the<br />
designer should select structural glued laminated timber<br />
from NDS Supplement Table 5B. Similarly, structural glued<br />
laminated timber combinations in NDS Supplement Table<br />
5B are inefficiently utilized if the primary use is bending<br />
about the X-X axis.<br />
The reference design values given in NDS Supplement<br />
Tables 5A and 5B are based on use under normal duration<br />
of load (10 years) and dry conditions (less than 16%<br />
moisture content). When used under other conditions,<br />
see NDS Chapter 5 for adjustment factors. The reference<br />
bending design values are based on members loaded as<br />
simple beams. When structural glued laminated timber is<br />
used in continuous or cantilevered beams, the reference<br />
bending design values given in NDS Supplement Table 5A<br />
for compression zone stressed in tension should be used<br />
for the design of stress reversal.<br />
Figure M5.2-1<br />
X<br />
Y<br />
Y<br />
X-X Axis Loading<br />
Loading in the X-X<br />
and Y-Y Axes<br />
X<br />
Y<br />
X<br />
X<br />
Y-Y Axis Loading<br />
Y<br />
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31<br />
M5.3 Adjustment of Reference Design Values<br />
The adjustment factors provided in the NDS are for<br />
non-reference end-use conditions and material modification<br />
effects. These factors shall be used to modify the<br />
reference design values when one or more of the specific<br />
end uses or material modification conditions are beyond<br />
the limits of the reference conditions given in the NDS.<br />
Adjustment factors unique to structural glued laminated<br />
timber include the volume factor, C V , and the curvature<br />
factor, C c . Both are defined in Chapter 5 of the NDS.<br />
To generate member design capacities, reference<br />
design values for structural glued laminated timber are<br />
multiplied by adjustment factors and section properties per<br />
Chapter M3. Applicable adjustment factors for structural<br />
glued laminated timber are defined in NDS 5.3. Table<br />
M5.3-1 shows the applicability of adjustment factors for<br />
structural glued laminated timber in a slightly different<br />
format for the designer.<br />
Table M5.3-1<br />
Applicability of Adjustment Factors for Structural Glued<br />
Laminated Timber 1<br />
Allowable Stress Design<br />
Load and Resistance Factor Design<br />
F b ′ = F b C D C M C t C L C V C fu C c<br />
F b ′ = F b C M C t C L C V C fu C c K F φ b λ<br />
F t ′ = F t C D C M C t<br />
F t ′ = F t C M C t K F φ t λ<br />
F v ′ = F v C D C M C t<br />
F v ′ = F v C M C t K F φ v λ<br />
F c⊥ ′ = F c⊥ C M C t C b<br />
F c⊥ ′ = F c⊥ C M C t C b K F φ c λ<br />
F c ′ = F c C D C M C t C P<br />
F c ′ = F c C M C t C P K F φ c λ<br />
E′ = E C M C t E′ = E C M C t<br />
E min ′ = E min C M C t<br />
E min ′ = E min C M C t K F φ s<br />
1. The beam stability factor, C L , shall not apply simultaneously with the volume factor, C V , for structural glued laminated timber bending members (see NDS 5.3.6).<br />
Therefore, the lesser of these adjustment factors shall apply.<br />
Bending Member Example<br />
For straight, laterally supported bending members<br />
loaded perpendicular to the wide face of the laminations<br />
and used in a normal building environment (meeting the<br />
reference conditions of NDS 2.3 and 5.3), the adjusted<br />
design values reduce to:<br />
Axially Loaded Member Example<br />
For axially loaded members used in a normal building<br />
environment (meeting the reference conditions of NDS<br />
2.3 and 5.3) designed to resist tension or compression<br />
loads, the adjusted tension or compression design values<br />
reduce to:<br />
5<br />
M5: STRUCTURAL GLUED LAMINATED TIMBER<br />
For <strong>ASD</strong>:<br />
F b ′ = F b C D C V<br />
F v ′ = F v C D<br />
F c⊥ ′ = F c⊥ C b<br />
E′ = E<br />
E min ′ = E min<br />
For <strong>LRFD</strong>:<br />
F b ′ = F b C V K F φ b λ<br />
F v ′ = F v K F φ v λ<br />
F c⊥ ′ = F c⊥ C b K F φ c λ<br />
E′ = E<br />
For <strong>ASD</strong>:<br />
F c ′ = F c C D C P<br />
F t ′ = F t C D<br />
E min ′ = E min<br />
For <strong>LRFD</strong>:<br />
F c ′ = F c C P K F φ c λ<br />
F t ′ = F t K F φ t λ<br />
E min ′ = E min K F φ s<br />
E min ′ = E min K F φ s<br />
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32 M5: structural glued laminated timber<br />
M5.4 Special Design Considerations<br />
General<br />
The section contains information concerning physical<br />
properties of structural glued laminated timber members<br />
including specific gravity and response to moisture or<br />
temperature.<br />
In addition to designing to accommodate dimensional<br />
changes and detailing for durability, another significant<br />
issue in the planning of wood structures is that of fire<br />
performance, which is discussed in Chapter M16.<br />
Specific Gravity<br />
Table M5.4-1 provides specific gravity values for some<br />
of the most common wood species used for structural glued<br />
laminated timber. These values are used in determining<br />
various physical and connection properties. Further, weight<br />
factors are provided at four moisture contents. When the<br />
cross-sectional area (in. 2 ) is multiplied by the appropriate<br />
weight factor, it provides the weight of the structural glued<br />
laminated timber member per linear foot of length. For<br />
other moisture contents, the tabulated weight factors can<br />
be interpolated or extrapolated.<br />
Structural glued laminated timber members often are<br />
manufactured using different species at different portions<br />
of the cross section. In this case the weight of the structural<br />
glued laminated timber may be computed by the sum of<br />
the products of the cross-sectional area and the weight<br />
factor for each species.<br />
Dimensional Changes<br />
See M4.4 for information on calculating dimensional<br />
changes due to moisture or temperature.<br />
Durability<br />
See M4.4 for information on detailing for durability.<br />
Table M5.4-1<br />
Average Specific Gravity and Weight Factor<br />
Weight Factor 2<br />
Species Combination Specific Gravity 1 12% 15% 19% 25%<br />
California Redwood (close grain) 0.44 0.195 0.198 0.202 0.208<br />
Douglas Fir-Larch 0.50 0.235 0.238 0.242 0.248<br />
Douglas Fir (South) 0.46 0.221 0.225 0.229 0.235<br />
Eastern Spruce 0.41 0.191 0.194 0.198 0.203<br />
Hem-Fir 0.43 0.195 0.198 0.202 0.208<br />
Red Maple 0.58 0.261 0.264 0.268 0.274<br />
Red Oak 0.67 0.307 0.310 0.314 0.319<br />
Southern Pine 0.55 0.252 0.255 0.259 0.265<br />
Spruce-Pine-Fir (North) 0.42 0.195 0.198 0.202 0.208<br />
Yellow Poplar 0.43 0.213 0.216 0.220 0.226<br />
1. Specific gravity is based on weight and volume when ovendry.<br />
2. Weight factor shall be multiplied by net cross-sectional area in in. 2 to obtain weight in pounds per lineal foot.<br />
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33<br />
M6: ROUND<br />
TIMBER POLES<br />
AND PILES<br />
M6.1 General 34<br />
M6.2 Reference Design Values 34<br />
M6.3 Adjustment of Reference<br />
Design Values 35<br />
M6.4 Special Design Considerations 36<br />
6<br />
<strong>American</strong> Forest & paper association
34 M6: ROUND TIMBER POLES AND PILES<br />
M6.1 General<br />
Product Information<br />
Timber poles are used extensively in post-frame construction<br />
and are also used architecturally. This Chapter is<br />
not for use with poles used in the support of utility lines.<br />
Timber piles are generally used as part of foundation<br />
systems.<br />
Timber poles and piles offer many advantages relative<br />
to competing materials. As with other wood products,<br />
timber poles and piles offer the unique advantage of being<br />
the only major construction material that is a renewable<br />
resource.<br />
Common Uses<br />
Timber poles are used extensively in post-frame construction<br />
and are also used architecturally. This Chapter<br />
is not for use with poles used in the support of utility<br />
lines. Timber piles are generally used as part of foundation<br />
systems.<br />
Timber poles and piles offer many advantages relative<br />
to competing materials. As with other wood products,<br />
timber poles and piles offer the unique advantage of being<br />
the only major construction material that is a renewable<br />
resource.<br />
Availability<br />
Timber piles are typically available in four species:<br />
Pacific Coast Douglas-fir, southern pine, red oak, and red<br />
pine. However, local pile suppliers should be contacted<br />
because availability is dependent upon geographic location.<br />
Timber poles are supplied to the utility industry in<br />
a variety of grades and species. Because these poles are<br />
graded according to ANSI 05.1, Specifications and Dimensions<br />
for <strong>Wood</strong> Poles, they must be regraded according to<br />
ASTM D3200 if they are to be used with the NDS.<br />
M6.2 Reference Design Values<br />
General<br />
The tables in NDS Chapter 6 provide reference design<br />
values for timber pole and pile members. These reference<br />
design values are used when manual calculation of member<br />
strength is required and shall be used in conjunction with<br />
adjustment factors specified in NDS Chapter 6.<br />
Pole Reference Design Values<br />
Reference design values for poles are provided in<br />
NDS Table 6B. These values, with the exception of F c ,<br />
are applicable for all locations in the pole. The F c values<br />
are for the tip of the pole and can be increased for Pacific<br />
Coast Douglas-fir and southern pine poles in accordance<br />
with NDS 6.3.9.<br />
Reference design values are applicable for wet exposure<br />
and for poles treated with a steam conditioning or<br />
Boultonizing process. For poles that are not treated, or are<br />
air-dried or kiln-dried prior to treating, the factors in NDS<br />
6.3.5 shall be applied.<br />
Pile Reference Design Values<br />
Reference design values for piles are provided in<br />
NDS Table 6A. These values, with the exception of F c ,<br />
are applicable at any location along the length of the pile.<br />
The tabulated F c values for Pacific Coast Douglas-fir and<br />
southern pine may be increased for locations other than<br />
the tip as provided by NDS 6.3.9.<br />
Reference design values are applicable for wet exposures.<br />
These tabulated values are given for air-dried piles<br />
treated with a preservative using a steam conditioning or<br />
Boultonizing process. For piles that are not treated, or are<br />
air-dried or kiln-dried prior to treating, the factors in NDS<br />
6.3.5 shall be applied.<br />
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35<br />
M6.3 Adjustment of Reference Design Values<br />
To generate member design capacities, reference<br />
design values are multiplied by adjustment factors and<br />
section properties. Adjustment factors unique to round<br />
timber poles and piles include the untreated factor, C u , the<br />
critical section factor, C cs , and the single pile factor, C sp .<br />
All are defined in Chapter 6 of the NDS.<br />
To generate member design capacities, reference design<br />
values for round timber poles and piles are multiplied<br />
by adjustment factors and section properties per Chapter<br />
M3. Applicable adjustment factors for round timber poles<br />
and piles are defined in NDS 6.3. Table M6.3-1 shows the<br />
applicability of adjustment factors for round timber poles<br />
and piles in a slightly different format for the designer.<br />
Table M6.3-1<br />
Applicability of Adjustment Factors for Round Timber Poles and<br />
Piles 1<br />
6<br />
Allowable Stress Design<br />
Load and Resistance Factor Design<br />
F c ′ = F c C D C t C u C P C cs C sp<br />
F c ′ = F c C t C u C P C cs C sp K F φ c λ<br />
F b ′ = F b C D C t C u C F C sp<br />
F t ′ = F t C t C u C F C sp K F φ b λ<br />
F v ′ = F v C D C t C u<br />
F v ′ = F v C t C u K F φ v λ<br />
1<br />
F c⊥ ′ = F c⊥ C D C t C u C b<br />
F c⊥ ′ = F c⊥ C t C u C b K F φ c λ<br />
E′ = E C t E′ = E C t<br />
E min ′ = E min C t<br />
E min ′ = E min C t K F φ s<br />
1. The C D factor shall not apply to compression perpendicular to grain for poles.<br />
Axially Loaded Pole or Pile<br />
Example<br />
For single, axially loaded, treated poles or piles, fully<br />
laterally supported in two orthogonal directions, used in<br />
a normal environment (meeting the reference conditions<br />
of NDS 2.3 and 6.3), designed to resist compression loads<br />
only, and less than 13.5" in diameter, the adjusted compression<br />
design values reduce to:<br />
M6: ROUND TIMBER POLES AND PILES<br />
For <strong>ASD</strong>:<br />
F c ′ = F c C D C sp<br />
For <strong>LRFD</strong>:<br />
F c ′ = F c C sp K F φ c λ<br />
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36 M6: ROUND TIMBER POLES AND PILES<br />
M6.4 Special Design Considerations<br />
With proper detailing and protection, timber poles and<br />
piles can perform well in a variety of environments. One<br />
key to proper detailing is planning for the natural shrinkage<br />
and swelling of wood products as they are subjected<br />
to various drying and wetting cycles. While moisture<br />
changes have the largest impact on product dimensions,<br />
some designs must also check the effects of temperature.<br />
See M4.4 for design information on dimensional changes<br />
due to moisture and temperature.<br />
Durability issues related to piles are generally both<br />
more critical and more easily accommodated. Since piles<br />
are in constant ground contact, they cannot be “insulated”<br />
from contact with moisture – thus, the standard reference<br />
condition for piles is preservatively treated. The importance<br />
of proper treatment processing of piles cannot be<br />
overemphasized. See M4.4 for more information about<br />
durability.<br />
In addition to designing to accommodate dimensional<br />
changes and detailing for durability, another significant<br />
issue in the planning of wood structures is that of fire<br />
performance, which is discussed in Chapter M16.<br />
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37<br />
M7:<br />
PREFABRICATED<br />
WOOD I-JOISTS<br />
M7.1 General 38<br />
M7.2 Reference Design Values 38<br />
M7.3 Adjustment of Reference<br />
Design Values 40<br />
M7.4 Special Design Considerations 41<br />
7<br />
<strong>American</strong> Forest & paper association
38 M7: PREFABRICATED WOOD I-JOISTS<br />
M7.1 General<br />
Product Information<br />
I-joists are exceptionally stiff, lightweight, and capable<br />
of long spans. Holes may be easily cut in the web<br />
according to manufacturer’s recommendations, allowing<br />
ducts and utilities to be run through the joist. I-joists are<br />
dimensionally stable and uniform in size, with no crown.<br />
This keeps floors quieter, reduces field modifications, and<br />
eliminates rejects in the field. I-joists may be field cut to<br />
proper length using conventional methods and tools.<br />
Manufacturing of I-joists utilizes the geometry of the<br />
cross section and high strength components to maximize<br />
the strength and stiffness of the wood fiber. Flanges are<br />
manufactured from solid sawn lumber or structural composite<br />
lumber, while webs typically consist of plywood<br />
or oriented strand board. The efficient utilization of raw<br />
materials, along with high-quality exterior adhesives and<br />
state of the art quality control procedures, result in an extremely<br />
consistent product that maximizes environmental<br />
benefits as well.<br />
<strong>Wood</strong> I-joists are produced as proprietary products<br />
which are covered by code acceptance reports by one or<br />
all of the model building codes. Acceptance reports and<br />
product literature should be consulted for current design<br />
information.<br />
Common Uses<br />
Prefabricated wood I-joists are widely used as a framing<br />
material for housing in North America. I-joists are<br />
made in different grades and with various processes and<br />
can be utilized in various applications. Proper design is<br />
required to optimize performance and economics.<br />
In addition to use in housing, I-joists find increasing<br />
use in commercial and industrial construction. The high<br />
strength, stiffness, wide availability, and cost saving attributes<br />
make them a viable alternative in most low-rise<br />
construction projects.<br />
Prefabricated wood I-joists are typically used as floor<br />
and roof joists in conventional construction. In addition,<br />
I-joists are used as studs where long lengths and high<br />
strengths are required.<br />
Availability<br />
To efficiently specify I-joists for individual construction<br />
projects, consideration should be given to the size and<br />
the required strength of the I-joist. Sizes vary with each<br />
individual product. The best source of this information is<br />
your local lumber supplier, distribution center, or I-joist<br />
manufacturer. Proper design is facilitated through the use<br />
of manufacturer’s literature and specification software<br />
available from I-joist manufacturers.<br />
M7.2 Reference Design Values<br />
Introduction to Design Values<br />
As stated in NDS 7.2, each wood I-joist manufacturer<br />
develops its own proprietary design values. The derivation<br />
of these values is reviewed by the applicable building<br />
code authority. Since materials, manufacturing processes,<br />
and product evaluations may differ between the various<br />
manufacturers, selected design values are only appropriate<br />
for the specific product and application.<br />
To generate the design capacity of a given product, the<br />
manufacturer of that product evaluates test data. The design<br />
capacity is then determined per ASTM D5055.<br />
The latest model building code agency evaluation reports<br />
are a reliable source for wood I-joist design values.<br />
These reports list accepted design values for shear, moment,<br />
stiffness, and reaction capacity based on minimum<br />
bearing. In addition, evaluation reports note the limitations<br />
on web holes, concentrated loads, and requirements for<br />
web stiffeners.<br />
Bearing/Reaction Design<br />
Tabulated design capacities reflect standard conditions<br />
and must be modified as discussed in NDS Chapter 7 to<br />
obtain adjusted capacity values.<br />
Bearing lengths at supports often control the design<br />
capacity of an I-joist. Typically minimum bearing lengths<br />
are used to establish design parameters. In some cases<br />
additional bearing is available and can be verified in an<br />
installation. Increased bearing length means that the joist<br />
can support additional loading, up to the value limited by<br />
the shear capacity of the web material and web joint. Both<br />
interior and exterior reactions must be evaluated.<br />
Use of web stiffeners may be required and typically<br />
increases the bearing capacity of the joist. Correct installation<br />
is required to obtain the specified capacities.<br />
Additional loading from walls above will load the joist in<br />
bearing, further limiting the capacity of the joist if proper<br />
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
39<br />
end detailing is not followed. Additional information on<br />
bearing specifics can be found in M7.4.<br />
Adjusted bearing capacities, R r ′, are determined in the<br />
same empirical fashion as is allowable shear.<br />
Shear Design<br />
At end bearing locations, critical shear is the vertical<br />
shear at the ends of the design span. The practice of<br />
neglecting all uniform loads within a distance from the<br />
end support equal to the joist depth, commonly used for<br />
other wood materials, is not applicable to end supports for<br />
wood I-joists. At locations of continuity, such as interior<br />
supports of multi-span I-joists, the critical shear location<br />
for several wood I-joist types is located a distance equal<br />
to the depth of the joist from the centerline of bearing<br />
(uniform loads only). A cantilevered portion of a wood<br />
I-joist is generally not considered a location of continuity<br />
(unless the cantilever length exceeds the joist depth) and<br />
vertical shear at the cantilever bearing is the critical shear.<br />
Individual manufacturers, or the appropriate evaluation<br />
reports, should be consulted for reference to shear design<br />
at locations of continuity.<br />
Often, the adjusted shear capacities, V r ', are based on<br />
other considerations such as bottom flange bearing length<br />
or the installation of web stiffeners or bearing blocks.<br />
Moment Design<br />
Adjusted moment capacities, M r ′, of I-joists are determined<br />
from empirical testing of a completely assembled<br />
joist or by engineering analysis supplemented by tension<br />
testing the flange component. If the flange contains end<br />
jointed material, the allowable tension value is the lesser<br />
of the joint capacity or the material capacity.<br />
Because flanges of a wood I-joist can be highly<br />
stressed, field notching of the flanges is not allowed. Similarly,<br />
excessive nailing or the use of improper nail sizes<br />
can cause flange splitting that will also reduce capacity.<br />
The manufacturer should be contacted when evaluating a<br />
damaged flange.<br />
Deflection = Bending Component + Shear Component<br />
5w<br />
w<br />
∆ = +<br />
384EI<br />
k<br />
4 2<br />
(M7.2-1)<br />
Individual manufacturers provide equations in a similar<br />
format. Values for use in the preceding equation can be<br />
found in the individual manufacturer’s evaluation reports.<br />
For other load and span conditions, an approximate answer<br />
can be found by using conventional bending deflection<br />
equations adjusted as follows:<br />
⎛<br />
Deflection = Bending Deflection 1+<br />
384 EI ⎞<br />
⎜ ⎟<br />
⎝ 5 2 k ⎠<br />
where:<br />
w = uniform load in pounds per lineal inch<br />
= design span, in.<br />
E I = joist moment of inertia times flange<br />
modulus of elasticity<br />
k = shear deflection coefficient<br />
Since wood I-joists can have long spans, the model<br />
building code maximum live load deflection criteria may<br />
not be appropriate for many floor applications. Many wood<br />
I-joist manufacturers recommend using stiffer criteria,<br />
such as L/480 for residential floor construction and L/600<br />
for public access commercial applications such as office<br />
floors. The minimum code required criteria for storage<br />
floors and roof applications is normally adequate.<br />
7<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
Deflection Design<br />
<strong>Wood</strong> I-joists, due to their optimized web materials,<br />
are susceptible to the effects of shear deflection. This component<br />
of deflection can account for as much as 15% to<br />
30% of the total deflection. For this reason, both bending<br />
and shear deflection are considered in deflection design. A<br />
typical deflection calculation for simple span wood I-joists<br />
under uniform load is shown in Equation M7.2-1.<br />
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40 M7: PREFABRICATED WOOD I-JOISTS<br />
M7.3 Adjustment of Reference Design Values<br />
General<br />
Member design capacity is the product of reference<br />
design values and adjustment factors. Reference design<br />
values for I-joists are discussed in M7.2.<br />
The design values listed in the evaluation reports are<br />
generally applicable to dry use conditions. Less typical<br />
conditions, such as high moisture, high temperatures, or<br />
pressure impregnated chemical treatments, typically result<br />
in strength and stiffness adjustments different from those<br />
used for sawn lumber. NDS 7.3 outlines adjustments to<br />
design values for I-joists; however, individual wood I-joist<br />
manufacturers should be consulted to verify appropriate<br />
adjustments. Table M7.3-1 shows the applicability of<br />
adjustment factors for prefabricated wood I-joists in a<br />
slightly different format for the designer.<br />
Table M7.3-1<br />
Applicability of Adjustment Factors for Prefabricated <strong>Wood</strong><br />
I-Joists<br />
Allowable Stress Design<br />
M r ′ = M r C D C M C t C L C r<br />
V r ′ = V r C D C M C t<br />
R r ′ = R r C D C M C t<br />
EI′ = EI C M C t<br />
EI min ′ = EI min C M C t<br />
Bending Member Example<br />
For fully laterally supported bending members loaded<br />
in strong axis bending and used in a normal building environment<br />
(meeting the reference conditions of NDS 2.3<br />
and 7.3), the adjusted design values reduce to:<br />
For <strong>ASD</strong>:<br />
M r ′ = M r C D<br />
V r ′ = V r C D<br />
R r ′ = R r C D<br />
E I ′ = E I<br />
K′ = K<br />
For <strong>LRFD</strong>:<br />
M r ′ = M r K F φ b λ<br />
V r ′ = V r K F φ v λ<br />
R r ′ = R r K F φ v λ<br />
EI′ = EI<br />
K′ = K<br />
Load and Resistance Factor Design<br />
M r ′ = M r C M C t C L C r K F φ b λ<br />
V r ′ = V r C D C M C t K F φ v λ<br />
R r ′ = R r C M C t K F φ v λ<br />
EI′ = EI C M C t<br />
EI min ′ = EI min C M C t K F φ s<br />
The user is cautioned that manufacturers may not<br />
permit the use of some applications and/or treatments.<br />
Unauthorized treatments can void a manufacturer’s warranty<br />
and may result in structural deficiencies.<br />
Lateral Stability<br />
The design values contained in the evaluation reports<br />
assume continuous lateral restraint of the joist’s compression<br />
edge and lateral torsional restraint at the support<br />
locations. Lateral restraint is generally provided by diaphragm<br />
sheathing or bracing spaced at 16" on center or<br />
less (based on 1½" width joist flanges) nailed to the joist’s<br />
compression flange.<br />
Applications without continuous lateral bracing will<br />
generally have reduced moment design capacities. The<br />
reduced capacity results from the increased potential for<br />
lateral buckling of the joist’s compression flange. Consultation<br />
with individual manufacturers is recommended for all<br />
applications without continuous lateral bracing.<br />
Special Loads or Applications<br />
<strong>Wood</strong> I-joists are configured and optimized to act<br />
primarily as joists to resist bending loads supported at<br />
the bearing by the bottom flange. Applications that result<br />
in significant axial tension or compression loads, require<br />
web holes, special connections, or other unusual conditions<br />
should be evaluated only with the assistance of the<br />
individual wood I-joist manufacturers.<br />
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
41<br />
M7.4 Special Design Considerations<br />
Introduction<br />
The wood I-joist is similar to conventional lumber in<br />
that it is based on the same raw materials, but differs in how<br />
the material is composed. For this reason, conventional<br />
lumber design practices are not always compatible with<br />
the unique configuration and wood fiber orientation of the<br />
wood I-joist. Designers using wood I-joists should develop<br />
solutions in accordance with the following guidelines.<br />
Durability issues cannot be overemphasized. See M4.4<br />
for more information about durability.<br />
In addition to detailing for durability, another significant<br />
issue in the planning of wood structures is that of fire<br />
performance, which is discussed in NDS Chapter 16.<br />
Design Span<br />
The design span used for determining critical shears<br />
and moments is defined as the clear span between the<br />
faces of support plus one-half the minimum required<br />
bearing on each end (see Figure M7.4-1). For most wood<br />
I-joists, the minimum required end bearing length varies<br />
from 1½" to 3½" (adding 2" to the clear span dimension<br />
is a good estimate for most applications). At locations of<br />
continuity over intermediate bearings, the design span is<br />
measured from the centerline of the intermediate support<br />
to the face of the bearing at the end support, plus one-half<br />
the minimum required bearing length. For interior spans of<br />
a continuous joist, the design span extends from centerline<br />
to centerline of the intermediate bearings.<br />
Figure M7.4-1<br />
Design Span Determination<br />
7<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
<strong>American</strong> Forest & paper association
42 M7: PREFABRICATED WOOD I-JOISTS<br />
Load Cases<br />
Most building codes require consideration of a<br />
critical distribution of loads. Due to the long length and<br />
continuous span capabilities of the wood I-joist, these<br />
code provisions have particular meaning. Considering a<br />
multiple span member, the following design load cases<br />
should be considered:<br />
• All spans with total loads<br />
• Alternate span loading<br />
• Adjacent span loading<br />
• Partial span loading (joists with holes)<br />
• Concentrated load provisions (as occurs)<br />
A basic description of each of these load cases follows:<br />
Total loads on all spans – This load case involves<br />
placing all live and dead design loads on all spans simultaneously.<br />
Alternate span loading – This load case places the<br />
L, L R , S, or R load portion of the design loads on every<br />
other span and can involve two loading patterns. The first<br />
pattern results in the removal of the live loads from all<br />
even numbered spans. The second pattern removes live<br />
loads from all odd numbered spans. For roof applications,<br />
some building codes require removal of only a portion<br />
of the live loads from odd or even numbered spans. The<br />
alternate span load case usually generates maximum end<br />
reactions, mid-span moments, and mid-span deflections.<br />
Illustrations of this type of loading are shown in Figure<br />
M7.4-2.<br />
Adjacent span loading – This load case (see Figure<br />
M7.4-2) removes L, L R , S or R loads from all but two<br />
adjoining spans. All other spans, if they exist, are loaded<br />
with dead loads only. Depending on the number of spans<br />
involved, this load case can lead to a number of load patterns.<br />
All combinations of adjacent spans become separate<br />
loadings. This load case is used to develop maximum<br />
shears and reactions at internal bearing locations.<br />
Partial span loading – This load case involves applying<br />
L, L R , S or R loads to less than the full length of<br />
a span (see Figure M7.4-2). For wood I-joists with web<br />
holes, this case is used to develop shear at hole locations.<br />
When this load case applies, uniform L, L R , S, R load is<br />
applied only from an adjacent bearing to the opposite edge<br />
of a rectangular hole (centerline of a circular hole). For<br />
each hole within a given span, there are two corresponding<br />
load cases. Live loads other than the uniform application<br />
load, located within the span containing the hole, are also<br />
applied simultaneously. This includes all special loads<br />
such as point or tapered loads.<br />
Concentrated load provisions – Most building codes<br />
have a concentrated load (live load) provision in addition<br />
to standard application design loads. This load case considers<br />
this concentrated load to act in combination with<br />
the system dead loads on an otherwise unloaded floor or<br />
roof. Usually, this provision applies to non-residential<br />
construction. An example is the “safe” load applied over<br />
a 2½ square foot area for office floors. This load case<br />
helps insure the product being evaluated has the required<br />
shear and moment capacity throughout it’s entire length<br />
and should be considered when analyzing the effect of<br />
web holes.<br />
A properly designed multiple span member requires<br />
numerous load case evaluations. Most wood I-joist manufacturers<br />
have developed computer programs, load and<br />
span tables, or both that take these various load cases into<br />
consideration.<br />
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43<br />
Figure M7.4-2<br />
Load Case Evaluations<br />
7<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
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44 M7: PREFABRICATED WOOD I-JOISTS<br />
Floor Performance<br />
Designing a floor system to meet the minimum requirements<br />
of a building code may not always provide<br />
acceptable performance to the end user. Although minimum<br />
criteria help assure a floor system can safely support<br />
the imposed loads, the system ultimately must perform to<br />
the satisfaction of the end user. Since expectancy levels<br />
may vary from one person to another, designing a floor<br />
system becomes a subjective issue requiring judgment as<br />
to the sensitivity of the intended occupant.<br />
Joist deflection is often used as the primary means<br />
for designing floor performance. Although deflection is a<br />
factor, there are other equally important variables that can<br />
influence the performance of a floor system. A glue-nailed<br />
floor system will generally have better deflection performance<br />
than a nailed only system. Selection of the decking<br />
material is also an important consideration. Deflection of<br />
the sheathing material between joists can be reduced by<br />
placing the joists at a closer on center spacing or increasing<br />
the sheathing thickness.<br />
Proper installation and job site storage are important<br />
considerations. All building materials, including wood<br />
I-joists, need to be kept dry and protected from exposure<br />
to the elements. Proper installation includes correct spacing<br />
of sheathing joints, care in fastening of the joists and<br />
sheathing, and providing adequate and level supports. All<br />
of these considerations are essential for proper system<br />
performance.<br />
Vibration may be a design consideration for floor<br />
systems that are stiff and where very little dead load (i.e.,<br />
partition walls, ceilings, furniture, etc.) exists. Vibration<br />
can generally be damped with a ceiling system directly<br />
attached to the bottom flange of the wood I-joists. Effective<br />
bridging or continuous bottom flange nailers (i.e., 2x4<br />
nailed flat-wise and perpendicular to the joist and tied off<br />
to the end walls) can also help minimize the potential for<br />
vibration in the absence of a direct applied ceiling. Limiting<br />
the span/depth ratio of the I-joist may also improve<br />
floor performance.<br />
Joist Bearing<br />
Bearing design for wood I-joists requires more than<br />
consideration of perpendicular to grain bearing values.<br />
Minimum required bearing lengths take into account a<br />
number of considerations. These include: cross grain<br />
bending and tensile forces in the flanges, web stiffener<br />
connection to the joist web, adhesive joint locations and<br />
strength, and perpendicular to grain bearing stresses. The<br />
model building code evaluation reports provide a source<br />
for bearing design information, usually in the form of<br />
minimum required bearing lengths.<br />
Usually, published bearing lengths are based on the<br />
maximum allowable shear capacity of the particular<br />
product and depth or allowable reactions are related to<br />
specific bearing lengths. Bearing lengths for wood I-joists<br />
are most often based on empirical test results rather than a<br />
calculated approach. Each specific manufacturer should be<br />
consulted for information when deviations from published<br />
criteria are desired.<br />
To better understand the variables involved in a wood<br />
I-joist bearing, it’s convenient to visualize the member as<br />
a composition of pieces, each serving a specific task. For<br />
a typical simple span joist, the top flange is a compression<br />
member, the bottom flange is a tension member, and the<br />
web resists the vertical shear forces. Using this concept,<br />
shear forces accumulate in the web member at the bearing<br />
locations and must be transferred through the flanges to<br />
the support structure. This transfer involves two critical<br />
interfaces: between the flange and support member and<br />
between the web and flange materials.<br />
Starting with the support member, flange to support<br />
bearing involves perpendicular to grain stresses. The lowest<br />
design value for either the support member or flange<br />
material is usually used to develop the minimum required<br />
bearing area.<br />
The second interface to be checked is between the<br />
lower joist flange and the bottom edge of the joist web,<br />
assuming a bottom flange bearing condition. This connection,<br />
usually a routed groove in the flange and a matching<br />
shaped profile on the web, is a glued joint secured with<br />
a waterproof structural adhesive. The contact surfaces<br />
include the sides and bottom of the routed flange.<br />
In most cases, the adhesive line stresses at this joint<br />
control the bearing length design. The effective bearing<br />
length of the web into the flange is approximately the<br />
length of flange bearing onto the support plus an incremental<br />
length related to the thickness and stiffness of the<br />
flange material.<br />
Since most wood I-joists have web shear capacity<br />
in excess of the flange to web joint strength, connection<br />
reinforcement is sometimes utilized. The most common<br />
method of reinforcement is the addition of web stiffeners<br />
(also commonly referred to as bearing blocks). Web<br />
stiffeners are vertically oriented wood blocks positioned<br />
on both sides of the web. Web stiffeners should be cut so<br />
that a gap of at least 1/8" is between the stiffener and the<br />
flange to avoid a force fit. Stiffeners are positioned tight<br />
to the bottom flange at bearing locations and snug to the<br />
bottom of the top flange beneath heavy point loads within<br />
a span. Figure M7.4-3 provides an illustration of a typical<br />
end bearing assembly.<br />
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Figure M7.4-3<br />
End Bearing Web Stiffeners (Bearing Block)<br />
7<br />
Web Stiffeners<br />
When correctly fastened to the joist web, web stiffeners<br />
transfer some of the load from the web into the top of<br />
the bottom flange. This reduces the loads on the web to<br />
flange joint. A pair of web stiffeners (one on each side)<br />
is usually mechanically connected to the web with nails<br />
or staples loaded in double shear. For some of the higher<br />
capacity wood I-joists, nailing and supplemental gluing<br />
with a structural adhesive is required. The added bearing<br />
capacity achievable with web stiffeners is limited by the<br />
allowable bearing stresses where the stiffeners contact<br />
the bearing flange and by their mechanical connection to<br />
the web.<br />
Web stiffeners also serve the implied function of<br />
reinforcing the web against buckling. Since shear capacity<br />
usually increases proportionately with the depth, web<br />
stiffeners are very important for deep wood I-joists. For<br />
example, a 30" deep wood I-joist may only develop 20%<br />
to 30% of its shear and bearing capacity without properly<br />
attached web stiffeners at the bearing locations. This is<br />
especially important at continuous span bearing locations,<br />
where reaction magnitudes can exceed simple span reactions<br />
by an additional 25%.<br />
Web stiffeners should be cut so that a gap of at least<br />
1/8" is between the stiffener and the top or bottom of the<br />
flange to avoid a force fit. Web stiffeners should be installed<br />
snug to the bottom flange for bearing reinforcement or snug<br />
to the top flange if under concentrated load from above.<br />
For shallow depth joists, where relatively low shear<br />
capacities are required, web stiffeners may not be needed.<br />
When larger reaction capacities are required, web stiffener<br />
reinforcement may be needed, especially where short<br />
bearing lengths are desired. Figure M7.4-4 illustrates the<br />
bearing interfaces.<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
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46 M7: PREFABRICATED WOOD I-JOISTS<br />
Figure M7.4-4<br />
Web Stiffener Bearing Interface<br />
Beveled End Cuts<br />
Beveled end cuts, where the end of the joist is cut on<br />
an angle (top flange does not project over the bearing,<br />
much like a fire cut), also requires special design consideration.<br />
Again the severity of the angle, web material,<br />
location of web section joints, and web stiffener application<br />
criteria effect the performance of this type of bearing<br />
condition. The specific wood I-joist manufacturers should<br />
be consulted for limits on this type of end cut.<br />
It is generally accepted that if a wood I-joist has the<br />
minimum required bearing length, and the top flange of<br />
the joist is not cut beyond the face of bearing (measured<br />
from a line perpendicular to the joist’s bottom flange),<br />
there is no reduction in shear or reaction capacity. This<br />
differs from the conventional lumber provision that suggests<br />
there is no decrease in shear strength for beveled<br />
cuts of up to an angle of 45 o . The reason involves the<br />
composite nature of the wood I-joist and how the member<br />
fails in shear and or bearing. Figure M7.4-5 provides<br />
an illustration of the beveled end cut limitation.<br />
Figure M7.4-5<br />
Beveled End Cut<br />
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47<br />
Sloped Bearing Conditions<br />
Sloped bearing conditions require design considerations<br />
different from conventional lumber. An example is<br />
a birdsmouth bearing cut (notches in the bottom flange, see<br />
Figure M7.4-6). This type of bearing should only be used<br />
on the low end bearing for wood I-joists. Another example<br />
is the use of metal joist support connectors that attach only<br />
to the web area of the joist and do not provide a bottom<br />
seat in which to bear. In general, this type of connector<br />
is not recommended for use with wood I-joists without<br />
consideration for the resulting reduced capacity.<br />
The birdsmouth cut is a good solution for the low end<br />
bearing when the slope is steep and the tangential loads<br />
are high (loads along the axis of the joist member). This<br />
assumes the quality of construction is good and the cuts<br />
are made correctly and at the right locations. This type of<br />
bearing cut requires some skill and is not easy to make,<br />
particularly with the wider flange joists. The bearing capacity,<br />
especially with high shear capacity members, may<br />
be reduced as a result of the cut since the effective flange<br />
bearing area is reduced. The notched cut will also reduce<br />
the member’s shear and moment capacity at a cantilever<br />
location.<br />
An alternative to a birdsmouth cut is a beveled bearing<br />
plate matching the joist slope or special sloped seat<br />
bearing hardware manufactured by some metal connector<br />
suppliers. These alternatives also have special design considerations<br />
with steep slope applications. As the member<br />
slope increases, so does the tangential component of<br />
reaction, sometimes requiring additional flange to bearing<br />
nailing or straps to provide resistance. Figure M7.4-6<br />
shows some examples of acceptable low end bearing<br />
conditions.<br />
Figure M7.4-6<br />
Sloped Bearing Conditions (Low End)<br />
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For the high end support, bottom flange bearing in a<br />
suitable connector or on a beveled plate is recommended.<br />
When slopes exceed 30°, straps or gussets may be needed<br />
to resist the tangential component of the reaction.<br />
Support connections only to the web area of a wood<br />
I-joist, especially at the high end of a sloped application,<br />
are not generally recommended. Since a wood I-joist is<br />
comprised of a number of pieces, joints between web sections<br />
occurring near the end of the member may reduce<br />
the joist’s shear capacity when not supported from the<br />
bottom flange.<br />
When a wood I-joist is supported from the web only,<br />
the closest web to web joint from the end may be stressed<br />
in tension. This could result in a joint failure with the<br />
web section pulling out of the bottom flange. Locating<br />
these internal joints away from the end of the member or<br />
applying joint reinforcements are potential remedies, but<br />
generally are not practical in the field.<br />
The best bearing solution is to provide direct support<br />
to the joist’s bottom flange to avoid reductions in<br />
capacity. Figure M7.4-7 shows typical high end bearing<br />
conditions.<br />
Figure M7.4-7<br />
Sloped Bearing Conditions (High End)<br />
Connector Design/Joist Hangers<br />
Although there are numerous hangers and connectors<br />
available that are compatible with wood I-joists, many are<br />
not. Hangers developed for conventional lumber or glulam<br />
beams often use large nails and space them in a pattern<br />
that will split the joist flanges and web stiffeners. Hanger<br />
selection considerations for wood I-joists should include<br />
nail length and diameter, nail location, wood I-joist bearing<br />
capacity, composition of the supporting member, physical<br />
fit, and load capacity. For example, hangers appropriate<br />
for a wood I-joist to glulam beam support may not be<br />
compatible for an I-joist to I-joist connection.<br />
In general, nails into the flanges should not exceed<br />
the diameter of a 10d common nail, with a recommended<br />
length no greater than 1½". Nails into web stiffeners should<br />
not exceed the diameter of a 16d common nail. Nails<br />
through the sides of the hanger, when used in combination<br />
with web stiffeners, can be used to reduce the joist’s<br />
minimum required bearing length. Nails help transfer loads<br />
directly from the I-joist web into the hanger, reducing<br />
the load transferred through direct bearing in the bottom<br />
hanger seat.<br />
Hangers should be capable of providing lateral support<br />
to the top flange of the joist. This is usually accomplished<br />
by a hanger flange that extends the full depth of the joist.<br />
As a minimum, hanger support should extend to at least<br />
mid-height of a joist used with web stiffeners. Some connector<br />
manufacturers have developed hangers specifically<br />
for use with wood I-joists that provide full lateral support<br />
without the use of web stiffeners. Figure M7.4-8 illustrates<br />
lateral joist support requirements for hangers.<br />
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Figure M7.4-8<br />
Lateral Support Requirements for Joists in Hangers<br />
When top flange style hangers are used to support one<br />
I-joist from another, especially the wider flange I-joists,<br />
web stiffeners need to be installed tight to the bottom<br />
side of the support joist’s top flanges. This prevents cross<br />
grain bending and rotation of the top flange (see Figure<br />
M7.4-9).<br />
When face-nail hangers are used for joist to joist<br />
connections, nails into the support joist should extend<br />
through and beyond the web element (Figure M7.4-10).<br />
Figure M7.4-9<br />
Top Flange Hanger Support<br />
Filler blocks should also be attached sufficiently to provide<br />
support for the hanger. Again, nail diameter should be<br />
considered to avoid splitting the filler block material.<br />
Multiple I-joists need to be adequately connected<br />
together to achieve desired performance. This requires<br />
proper selection of a nailing or bolting pattern and attention<br />
to web stiffener and blocking needs. Connections<br />
should be made through the webs of the I-joists and never<br />
through the flanges.<br />
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50 M7: PREFABRICATED WOOD I-JOISTS<br />
For a double I-joist member loaded from one side<br />
only, the minimum connection between members should<br />
be capable of transferring at least 50% of the applied<br />
load. Likewise, for a triple member loaded from one side<br />
only, the minimum connection between members must<br />
be capable of transferring at least 2/3 of the applied load.<br />
The actual connection design should consider the potential<br />
slip and differential member stiffness. Many manufacturers<br />
recommend limiting multiple members to three joists.<br />
Multiple I-joists with 3½" wide flanges may be further<br />
limited to two members.<br />
The low torsional resistance of most wood I-joists is<br />
also a design consideration for joist to joist connections.<br />
Eccentrically applied side loads, such as a top flange<br />
hanger hung from the side of a double joist, create the<br />
potential for joist rotation. Bottom flange restraining<br />
straps, blocking, or directly applied ceiling systems may<br />
be needed on heavily loaded eccentric connections to resist<br />
rotation. Figure M7.4-10 shows additional I-joist connection<br />
considerations for use with face nail hangers.<br />
Figure M7.4-10 Connection Requirements for Face Nail Hangers<br />
Vertical Load Transfer<br />
Bearing loads originating above the joists at the bearing<br />
location require blocking to transfer these loads around<br />
the wood I-joist to the supporting wall or foundation. This<br />
is typically the case in a multi-story structure where bearing<br />
walls stack and platform framing is used. Usually, the<br />
available bearing capacity of the joist is needed to support<br />
its reaction, leaving little if any excess capacity to support<br />
additional bearing wall loads from above.<br />
The most common type of blocking uses short pieces<br />
of wood I-joist, often referred to as blocking panels,<br />
positioned directly over the lower bearing and cut to fit<br />
in between the joists. These panels also provide lateral<br />
support for the joists and an easy means to transfer lateral<br />
diaphragm shears.<br />
The ability to transfer lateral loads (due to wind, seismic,<br />
construction loads, etc.) to shear walls or foundations<br />
below is important to the integrity of the building design.<br />
Compared with dimension lumber blocking, which usually<br />
is toe-nailed to the bearing below, wood I-joist blocking<br />
can develop higher diaphragm transfer values because of<br />
a wider member width and better nail values.<br />
Specialty products designed specifically for rim boards<br />
are pre-cut in strips equal to the joist depth and provide<br />
support for the loads from above. This solution may also<br />
provide diaphragm boundary nailing for lateral loads.<br />
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A third method uses vertically oriented short studs,<br />
often called squash blocks or cripple blocks, on each side<br />
of the joist and cut to a length slightly longer than the depth<br />
of the joist. This method should be used in combination<br />
with some type of rim joist or blocking material when<br />
lateral stability or diaphragm transfer is required.<br />
The use of horizontally oriented sawn lumber as a<br />
blocking material is unacceptable. <strong>Wood</strong> I-joists generally<br />
do not shrink in the vertical direction due to their panel<br />
type web, creating the potential for a mismatch in height<br />
as sawn lumber shrinks to achieve equilibrium. When<br />
conventional lumber is used in the vertical orientation,<br />
shrinkage problems are not a problem because changes in<br />
elongation due to moisture changes are minimal. Figure<br />
M7.4-11 shows a few common methods for developing<br />
vertical load transfer.<br />
Figure M7.4-11 Details for Vertical Load Transfer<br />
7<br />
Web Holes<br />
Holes cut in the web area of a wood I-joist affect the<br />
member’s shear capacity. Usually, the larger the hole, the<br />
greater the reduction in shear capacity. For this reason,<br />
holes are generally located in areas where shear stresses<br />
are low. This explains why the largest holes are generally<br />
permitted near mid-span of a member. The required<br />
spacing between holes and from the end of the member is<br />
dependent upon the specific materials and processes used<br />
during manufacturing.<br />
The allowable shear capacity of a wood I-joist at<br />
a hole location is influenced by a number of variables.<br />
These include: percentage of web removed, proximity to<br />
a vertical joint between web segments, the strength of the<br />
web to flange glue joint, the stiffness of the flange, and<br />
the shear strength of the web material. Since wood I-joists<br />
are manufactured using different processes and materials,<br />
each manufacturer should be consulted for the proper web<br />
hole design.<br />
The methodology used to analyze application loads is<br />
important in the evaluation of web holes. All load cases<br />
that will develop the highest shear at the hole location<br />
should be considered. Usually, for members resisting<br />
simple uniform design loads, the loading condition that<br />
develops the highest shear loads in the center area of a<br />
joist span involves partial span loading.<br />
Web holes contribute somewhat to increased deflection.<br />
The larger the hole the larger the contribution.<br />
Provided not too many holes are involved, the contribution<br />
is negligible. In most cases, if the manufacturer’s hole<br />
criteria are followed and the number of holes is limited to<br />
three or less per span, the additional deflection does not<br />
warrant consideration.<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
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52<br />
M7: PREFABRICATED WOOD I-JOISTS<br />
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53<br />
M8: STRUCTURAL<br />
COMPOSITE<br />
LUMBER<br />
M8.1 General 54<br />
M8.2 Reference Design Values 55<br />
M8.3 Adjustment of Reference<br />
Design Values 56<br />
M8.4 Special Design Considerations 57<br />
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54 M8: STRUCTURAL COMPOSITE LUMBER<br />
M8.1 General<br />
Product Information<br />
Structural composite lumber (SCL) products are well<br />
known throughout the construction industry. The advantages<br />
of SCL include environmental benefits from better<br />
wood fiber utilization along with higher strength, stiffness,<br />
and consistency from fiber orientation and manufacturing<br />
process control.<br />
SCL is manufactured from strips or full sheets of<br />
veneer. The process typically includes alignment of stress<br />
graded fiber, application of adhesive, and pressing the<br />
material together under heat and pressure. By redistributing<br />
natural defects and through state of the art quality<br />
control procedures, the resulting material is extremely<br />
consistent and maximizes the strength and stiffness of<br />
the wood fiber.<br />
The material is typically produced in a long length<br />
continuous or fixed press in a billet form. This is then<br />
resawn into required dimensions for use. Material is currently<br />
available in a variety of depths from 4-3/8" to 24"<br />
and thicknesses from 3/4" to 7".<br />
SCL is available in a wide range of sizes and grades.<br />
When specifying SCL products, a customer may specify<br />
on the basis of size, stress (strength), or appearance.<br />
SCL products are proprietary and are covered by<br />
code acceptance reports by one or all of the model building<br />
codes. Such reports should be consulted for current<br />
design information while manufacturer’s literature can<br />
be consulted for design information, sizing tables, and<br />
installation recommendations.<br />
Common Uses<br />
SCL is widely used as a framing material for housing.<br />
SCL is made in different grades and with various processes<br />
and can be utilized in numerous applications. Proper design<br />
is required to optimize performance and economics.<br />
In addition to use in housing, SCL finds increasing<br />
use in commercial and industrial construction. Its high<br />
strength, stiffness, universal availability, and cost saving<br />
attributes make it a viable alternative in most low-rise<br />
construction projects.<br />
SCL is used as beams, headers, joists, rafters, studs,<br />
and plates in conventional construction. In addition, SCL is<br />
used to fabricate structural glued laminated beams, trusses,<br />
and prefabricated wood I-joists.<br />
Availability<br />
SCL is regarded as a premium construction material<br />
and is widely available. To efficiently specify SCL for<br />
individual projects, the customer should be aware of the<br />
species and strength availability. Sizes vary with each<br />
individual product. The best source of this information<br />
is your local lumber supplier, distribution center, or SCL<br />
manufacturer. Proper design is facilitated through the use<br />
of manufacturer’s literature, code reports, and software<br />
available from SCL manufacturers.<br />
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55<br />
M8.2 Reference Design Values<br />
General<br />
Bending<br />
As stated in NDS 8.2, SCL products are proprietary<br />
and each manufacturer develops design values appropriate<br />
for their products. These values are reviewed by the<br />
model building codes and published in acceptance reports<br />
and manufacturer’s literature.<br />
Reference design values are used in conjunction with<br />
the adjustment factors in M8.3.<br />
Shear Design<br />
SCL is typically designed and installed as a rectangular<br />
section. Loads near supports may be reduced per NDS<br />
3.4.3.1. However, such load must be included in bearing<br />
calculations. Shear values for SCL products often change<br />
with member orientation.<br />
Bearing<br />
SCL typically has high F c and F c⊥ properties. With<br />
the higher shear and bending capacities, shorter or continuous<br />
spans are often controlled by bearing. The user is<br />
cautioned to ensure the design accounts for compression<br />
of the support material (i.e., plate) as well as the beam<br />
material. Often the plate material is of softer species and<br />
will control the design.<br />
Published bending capacities of SCL beams are determined<br />
from testing of production specimens. Adjustment<br />
for the size of the member is also determined by test.<br />
Field notching or drilling of holes is typically not allowed.<br />
Similarly, excessive nailing or the use of improper<br />
nail sizes can cause splitting that will also reduce capacity.<br />
The manufacturer should be contacted when evaluating a<br />
damaged beam.<br />
Deflection Design<br />
Deflection calculations for SCL typically are similar to<br />
provisions for other rectangular wood products (see M3.5).<br />
Values for use in deflection equations can be found in the<br />
individual manufacturer’s product literature or evaluation<br />
reports. Some manufacturers might publish “true” E values<br />
which would require additional calculations to account for<br />
shear deflection (see NDS Appendix F).<br />
8<br />
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56 M8: STRUCTURAL COMPOSITE LUMBER<br />
M8.3 Adjustment of Reference Design Values<br />
Member design capacity is the product of reference<br />
design values, adjustment factors, and section properties.<br />
Reference design values for SCL are discussed in M8.2.<br />
Adjustment factors are provided for applications<br />
outside the reference end-use conditions and for member<br />
configuration effects as specified in NDS 8.3. When one<br />
or more of the specific end use or member configuration<br />
conditions are beyond the range of the reference conditions,<br />
these adjustment factors shall be used to modify the<br />
appropriate property. Adjustment factors for the effects of<br />
moisture, temperature, member configuration, and size are<br />
provided in NDS 8.3. Additional adjustment factors can<br />
be found in the manufacturer’s product literature or code<br />
evaluation report. Table M8.3-1 shows the applicability of<br />
adjustment factors for SCL in a slightly different format<br />
for the designer.<br />
Certain products may not be suitable for use in some<br />
applications or with certain treatments. Such conditions<br />
can result in structural deficiencies and may void manufacturer<br />
warranties. The manufacturer or code evaluation<br />
report should be consulted for specific information.<br />
Table M8.3-1<br />
Applicability of Adjustment Factors for Structural Composite<br />
Lumber 1<br />
Allowable Stress Design<br />
F b ′ = F b C D C M C t C L C V C r<br />
F t ′ = F t C D C M C t<br />
F v ′ = F v C D C M C t<br />
F c⊥ ′ = F c⊥ C M C t C b<br />
F c ′ = F c C D C M C t C P<br />
Load and Resistance Factor Design<br />
F b ′ = F b C M C t C L C V C r K F φ b λ<br />
F t ′ = F t C M C t K F φ t λ<br />
F v ′ = F v C M C t K F φ v λ<br />
F c⊥ ′ = F c⊥ C M C t C b K F φ c λ<br />
F c ′ = F c C M C t C P K F φ c λ<br />
E′ = E C M C t E′ = E C M C t<br />
E min ′ = E min C M C t<br />
E min ′ = E min C M C t K F φ s<br />
1. See NDS 8.3.6 for information on simultaneous application of the volume factor, C V , and the beam stability factor, C L .<br />
Bending Member Example<br />
For fully laterally supported members stressed in<br />
strong axis bending and used in a normal building environment<br />
(meeting the reference conditions of NDS 2.3 and<br />
8.3), the adjusted design values reduce to:<br />
For <strong>ASD</strong>:<br />
F b ′ = F b C D C V<br />
F v ′ = F v C D<br />
F c⊥ ′ = F c⊥ C b<br />
E′ = E<br />
For <strong>LRFD</strong>:<br />
F b ′ = F b C V K F φ b λ<br />
F v ′ = F v K F φ v λ<br />
F c⊥ ′ = F c⊥ C b K F φ c λ<br />
Axially Loaded Member Example<br />
For axially loaded members used in a normal building<br />
environment (meeting the reference conditions of NDS 2.3<br />
and 8.3) designed to resist tension or compression loads,<br />
the adjusted tension or compression design values reduce<br />
to:<br />
For <strong>ASD</strong>:<br />
F c ′ = F c C D C P<br />
F t ′ = F t C D<br />
E min ′ = E min<br />
For <strong>LRFD</strong>:<br />
F c ′ = F c C P K F φ c λ<br />
F t ′ = F t K F φ t λ<br />
E min ′ = E min K F φ s<br />
E′ = E<br />
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57<br />
M8.4 Special Design Considerations<br />
General<br />
With proper detailing and protection, SCL can perform<br />
well in a variety of environments. One key to proper detailing<br />
is planning for the natural shrinkage and swelling<br />
of wood members as they are subjected to various drying<br />
and wetting cycles. While moisture changes have the largest<br />
impact on lumber dimensions, some designs must also<br />
check the effects of temperature. While SCL is typically<br />
produced using dry veneer, some moisture accumulation<br />
may occur during storage. If the product varies significantly<br />
from specified dimensions, the user is cautioned<br />
from using such product as it will “shrink” as it dries.<br />
In addition to designing to accommodate dimensional<br />
changes and detailing for durability, another significant<br />
issue in the planning of wood structures is that of fire<br />
performance, which is covered in Chapter M16.<br />
Dimensional Changes<br />
Durability<br />
Designing for durability is a key part of the architectural<br />
and engineering design of the building. <strong>Wood</strong><br />
exposed to high levels of moisture can decay over time.<br />
While there are exceptions – such as naturally durable species,<br />
preservative-treated wood, and those locations that<br />
can completely air-dry between moisture cycles – prudent<br />
design calls for a continuing awareness of the possibility of<br />
moisture accumulation. Awareness of the potential for decay<br />
is the key – many design conditions can be detailed to<br />
minimize the accumulation of moisture; for other problem<br />
conditions, preservative-treated wood or naturally durable<br />
species should be specified.<br />
This section cannot cover the topic of designing for<br />
durability in detail. There are many excellent texts that devote<br />
entire chapters to the topic, and designers are advised<br />
to use this information to assist in designing “difficult”<br />
design areas, such as:<br />
The dimensional stability and response to temperature<br />
effects of engineered lumber is similar to that of solid sawn<br />
lumber of the same species.<br />
Some densification of the wood fiber can occur in<br />
various manufacturing processes. SCL that is densified<br />
will result in a product that has more wood fiber in a given<br />
volume and can therefore hold more water than a solid<br />
sawn equivalent. When soaked these products expand and<br />
dimensional changes can occur.<br />
Adhesive applied during certain processes tends to<br />
form a barrier to moisture penetration. Therefore, the<br />
material will typically take longer to reach equilibrium<br />
than its solid sawn counterpart.<br />
For given temperatures and applications, different<br />
levels of relative humidity are present. This will cause the<br />
material to move toward an equilibrium moisture content<br />
(EMC). Eventually all wood products will reach their EMC<br />
for a given environment. SCL will typically equilibrate at<br />
a lower EMC (typically 3% to 4% lower) than solid sawn<br />
lumber and will take longer to reach an ambient EMC.<br />
Normal swings in humidity during the service life of<br />
the structure should not produce noticeable dimensional<br />
changes in SCL members.<br />
More information on designing for moisture and temperature<br />
change is included in M4.4.<br />
• structures in high moisture or humid conditions<br />
• where wood comes in contact with concrete<br />
or masonry<br />
• where wood members are supported in steel<br />
hangers or connectors in which condensation<br />
could collect<br />
• anywhere that wood is directly or indirectly<br />
exposed to the elements<br />
• where wood, if it should ever become wet,<br />
could not naturally dry out.<br />
This list is not intended to be all-inclusive – it is<br />
merely an attempt to alert designers to special conditions<br />
that may cause problems when durability is not considered<br />
in the design.<br />
More information on detailing for durability is included<br />
in M4.4.<br />
8<br />
M8: STRUCTURAL COMPOSITE LUMBER<br />
<strong>American</strong> Forest & paper association
58<br />
M8: STRUCTURAL COMPOSITE LUMBER<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> <strong>Manual</strong> for Engineered <strong>Wood</strong> Construction<br />
59<br />
M9: WOOD<br />
STRUCTURAL<br />
PANELS<br />
M9.1 General 60<br />
M9.2 Reference Design Values 60<br />
M9.3 Adjustment of Reference<br />
Design Values 66<br />
M9.4 Special Design Considerations 67<br />
9<br />
<strong>American</strong> Forest & paper association
60 M9: WOOD STRUCTURAL PANELS<br />
M9.1 General<br />
Product Description<br />
<strong>Wood</strong> structural panels are wood-based panel products<br />
that have been rated for use in structural applications. Common<br />
applications for wood structural panels include roof<br />
sheathing, wall sheathing, subflooring, and single-layer<br />
flooring (combination subfloor-underlayment). Plywood<br />
is also manufactured in various sanded grades.<br />
<strong>Wood</strong> structural panels are classified by span ratings.<br />
Panel span ratings identify the maximum recommended<br />
support spacings for specific end uses. Design capacities<br />
are provided on the basis of span ratings.<br />
Sanded grades are classed according to nominal thickness<br />
and design capacities are provided on that basis.<br />
Designers must specify wood structural panels by the<br />
span ratings, nominal thicknesses, grades, and constructions<br />
associated with tabulated design recommendations.<br />
Exposure durability classification must also be identified.<br />
Single Floor panels may have tongue-and-groove<br />
or square edges. If square edge Single Floor panels are<br />
specified, the specification shall require lumber blocking<br />
between supports.<br />
Table M9.1-1 provides descriptions and typical uses<br />
for various panel grades and types.<br />
M9.2 Reference Design Values<br />
General<br />
<strong>Wood</strong> structural panel design capacities listed in Tables<br />
M9.2-1 through M9.2-2 are minimum for grade and span<br />
rating. Multipliers shown in each table provide adjustments<br />
in capacity for Structural I panel grades. To take<br />
advantage of these multipliers, the specifier must insure<br />
that the correct panel is used in construction.<br />
The tabulated capacities and adjustment factors are<br />
based on data from tests of panels manufactured in accordance<br />
with industry standards and which bear the<br />
trademark of a qualified inspection and testing agency.<br />
Structural panels have a strength axis direction and<br />
a cross panel direction. The direction of the strength axis<br />
is defined as the axis parallel to the orientation of OSB<br />
face strands or plywood face veneer grain and is the long<br />
dimension of the panel unless otherwise indicated by the<br />
manufacturer. This is illustrated in Figure M9.2-1.<br />
Figure M9.2-1<br />
4-ft Typical<br />
Structural Panel with<br />
Strength Direction<br />
Across Supports<br />
Panel Stiffness and Strength<br />
Panel design capacities listed in Table M9.2-1 are based<br />
on flat panel bending (Figure M9.2-2) as measured by<br />
testing according to principles of ASTM D3043 Method<br />
C (large panel testing).<br />
Stiffness (EI)<br />
Panel bending stiffness is the capacity to resist deflection<br />
and is represented as EI. E is the reference modulus<br />
of elasticity of the material, and I is the moment of inertia<br />
of the cross section. The units of EI are lb-in. 2 per foot of<br />
panel width.<br />
Strength (F b S)<br />
Bending strength capacity is the design maximum<br />
moment, represented as F b S. F b is the reference extreme<br />
fiber bending stress of the material, and S is the section<br />
modulus of the cross section. The units of F b S are lb-in.<br />
per foot of panel width.<br />
Figure M9.2-2<br />
Example of Structural<br />
Panel in Bending<br />
8-ft Typical<br />
Strength<br />
Direction<br />
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61<br />
Table M9.1-1<br />
Guide to Panel Use<br />
Panel Grade Description & Use Common<br />
Nominal<br />
Thickness<br />
(in.)<br />
Sheathing<br />
EXP 1<br />
Structural I<br />
Sheathing<br />
EXP 1<br />
Single Floor<br />
EXP 1<br />
Underlayment<br />
EXP 1 or INT<br />
C-D-Plugged<br />
EXP 1<br />
Sanded Grades<br />
EXP 1 or INT<br />
Marine EXT<br />
Unsanded sheathing grade for wall, roof,<br />
subflooring, and industrial applications<br />
such as pallets and for engineering design<br />
with proper capacities. Manufactured with<br />
intermediate and exterior glue. For longterm<br />
exposure to weather or moisture, only<br />
Exterior type plywood is suitable.<br />
Panel grades to use where shear and crosspanel<br />
strength properties are of maximum<br />
importance. Made with exterior glue only.<br />
Plywood Structural I is made from all<br />
Group 1 woods.<br />
Combination subfloor-underlayment.<br />
Provides smooth surface for application<br />
of carpet and pad. Possesses high<br />
concentrated and impact load resistance<br />
during construction and occupancy.<br />
Manufactured with intermediate (plywood)<br />
and exterior glue. Touch-sanded. Available<br />
with tongue-and-groove edges.<br />
For underlayment under carpet and pad.<br />
Available with exterior glue. Touchsanded.<br />
Available with tongue-and-groove<br />
edges.<br />
For built-ins, wall and ceiling tile backing.<br />
Not for underlayment. Available with<br />
exterior glue. Touch-sanded.<br />
Generally applied where a high-quality<br />
surface is required. Includes APA N-N,<br />
N-A, N-B, N-D, A-A, A-D, B-B, and B-D<br />
INT grades.<br />
Superior Exterior-type plywood made only<br />
with Douglas-fir or western larch. Special<br />
solid-core construction. Available with<br />
medium density overlay (MDO) or high<br />
density overlay (HDO) face. Ideal for boat<br />
hull construction.<br />
5/16, 3/8,<br />
15/32, 1/2,<br />
19/32, 5/8,<br />
23/32, 3/4<br />
19/32, 5/8,<br />
23/32, 3/4<br />
19/32, 5/8,<br />
23/32, 3/4,<br />
7/8, 1, 1-3/32,<br />
1-1/8<br />
1/4, 11/32,<br />
3/8, 15/32,<br />
1/2, 19/32,<br />
5/8, 23/32,<br />
3/4<br />
1/2, 19/32,<br />
5/8, 23/32,<br />
3/4<br />
1/4, 11/32,<br />
3/8, 15/32,<br />
1/2, 19/32,<br />
5/8, 23/32,<br />
3/4<br />
1/4, 11/32,<br />
3/8, 15/32,<br />
1/2, 19/32,<br />
5/8, 23/32,<br />
3/4<br />
Panel Construction<br />
OSB COM-PLY Plywood<br />
& Veneer<br />
Grade<br />
Yes Yes Yes,<br />
face C,<br />
back D,<br />
inner D<br />
Yes Yes Yes,<br />
face C,<br />
back D,<br />
inner D<br />
Yes Yes Yes,<br />
face<br />
C-Plugged,<br />
back D,<br />
inner D<br />
No No Yes,<br />
face<br />
C-Plugged,<br />
back D,<br />
inner D<br />
No No Yes, face<br />
C-Plugged,<br />
back D,<br />
inner D<br />
No No Yes,<br />
face B or<br />
better, back<br />
D or better,<br />
inner C & D<br />
No No Yes,<br />
face A<br />
or face B,<br />
back A<br />
or inner B<br />
9<br />
M9: WOOD STRUCTURAL PANELS<br />
<strong>American</strong> Forest & paper association
62 M9: WOOD STRUCTURAL PANELS<br />
Table M9.2-1<br />
<strong>Wood</strong> Structural Panel Bending Stiffness and Strength<br />
Span<br />
Rating<br />
Stress Parallel to Strength Axis 1 Stress Perpendicular to Strength Axis 1<br />
Plywood<br />
Plywood<br />
3-ply 4-ply 5-ply OSB 3-ply 4-ply 5-ply OSB<br />
PANEL BENDING STIFFNESS, EI (lb-in. 2 /ft of panel width)<br />
24/0 66,000 66,000 66,000 60,000 3,600 7,900 11,000 11,000<br />
24/16 86,000 86,000 86,000 78,000 5,200 11,500 16,000 16,000<br />
32/16 125,000 125,000 125,000 115,000 8,100 18,000 25,000 25,000<br />
40/20 250,000 250,000 250,000 225,000 18,000 39,500 56,000 56,000<br />
48/24 440,000 440,000 440,000 400,000 29,500 65,000 91,500 91,500<br />
16oc 165,000 165,000 165,000 150,000 11,000 24,000 34,000 34,000<br />
20oc 230,000 230,000 230,000 210,000 13,000 28,500 40,500 40,500<br />
24oc 330,000 330,000 330,000 300,000 26,000 57,000 80,500 80,500<br />
32oc 715,000 715,000 715,000 650,000 75,000 165,000 235,000 235,000<br />
48oc 1,265,000 1,265,000 1,265,000 1,150,000 160,000 350,000 495,000 495,000<br />
Multiplier for<br />
Structural I Panels 1.0 1.0 1.0 1.0 1.5 1.5 1.6 1.6<br />
PANEL BENDING STRENGTH, F b S (lb-in./ft of panel width)<br />
24/0 250 275 300 300 54 65 97 97<br />
24/16 320 350 385 385 64 77 115 115<br />
32/16 370 405 445 445 92 110 165 165<br />
40/20 625 690 750 750 150 180 270 270<br />
48/24 845 930 1,000 1,000 225 270 405 405<br />
16oc 415 455 500 500 100 120 180 180<br />
20oc 480 530 575 575 140 170 250 250<br />
24oc 640 705 770 770 215 260 385 385<br />
32oc 870 955 1,050 1,050 380 455 685 685<br />
48oc 1,600 1,750 1,900 1,900 680 815 1,200 1,200<br />
Multiplier for<br />
Structural I Panels 1.0 1.0 1.0 1.0 1.3 1.4 1.5 1.5<br />
1. Strength axis is defined as the axis parallel to the face and back orientation of the flakes or the grain (veneer), which is generally the long panel direction, unless<br />
otherwise marked.<br />
Axial Capacities<br />
Axial Stiffness (EA)<br />
Panel axial stiffnesses listed in Table M9.2-2 are based<br />
on testing according to the principles of ASTM D3501<br />
Method B. Axial stiffness is the capacity to resist axial<br />
strain and is represented as EA. E is the reference axial<br />
modulus of elasticity of the material, and A is the area of<br />
the cross section. The units of EA are pounds per foot of<br />
panel width.<br />
Tension (F t A)<br />
Tension capacities listed in Table M9.2-2 are based<br />
on testing according to the principles of ASTM D3500<br />
Method B. Tension capacity is given as F t A. F t is the<br />
reference tensile stress of the material, and A is the area<br />
of the cross section. The units of F t A are pounds per foot<br />
of panel width.<br />
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63<br />
Table M9.2-2<br />
<strong>Wood</strong> Structural Panel Axial Stiffness, Tension, and<br />
Compression Capacities<br />
Span<br />
Rating<br />
Stress Parallel to Strength Axis 1 Stress Perpendicular to Strength Axis 1<br />
Plywood<br />
Plywood<br />
3-ply 4-ply 5-ply OSB 3-ply 4-ply 5-ply OSB<br />
PANEL TENSION, F t A (lb/ft of panel width)<br />
24/0 2,300 2,300 3,000 2,300 600 600 780 780<br />
24/16 2,600 2,600 3,400 2,600 990 990 1,300 1,300<br />
32/16 2,800 2,800 3,650 2,800 1,250 1,250 1,650 1,650<br />
40/20 2,900 2,900 3,750 2,900 1,600 1,600 2,100 2,100<br />
48/24 4,000 4,000 5,200 4,000 1,950 1,950 2,550 2,550<br />
16oc 2,600 2,600 3,400 2,600 1,450 1,450 1,900 1,900<br />
20oc 2,900 2,900 3,750 2,900 1,600 1,600 2,100 2,100<br />
24oc 3,350 3,350 4,350 3,350 1,950 1,950 2,550 2,550<br />
32oc 4,000 4,000 5,200 4,000 2,500 2,500 3,250 3,250<br />
48oc 5,600 5,600 7,300 5,600 3,650 3,650 4,750 4,750<br />
Multiplier for<br />
Structural I Panels 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0<br />
PANEL COMPRESSION, F c A (lb/ft of panel width)<br />
24/0 2,850 4,300 4,300 2,850 2,500 3,750 3,750 2,500<br />
24/16 3,250 4,900 4,900 3,250 2,500 3,750 3,750 2,500<br />
32/16 3,550 5,350 5,350 3,550 3,100 4,650 4,650 3,100<br />
40/20 4,200 6,300 6,300 4,200 4,000 6,000 6,000 4,000<br />
48/24 5,000 7,500 7,500 5,000 4,800 7,200 7,200 4,300<br />
16oc 4,000 6,000 6,000 4,000 3,600 5,400 5,400 3,600<br />
20oc 4,200 6,300 6,300 4,200 4,000 6,000 6,000 4,000<br />
24oc 5,000 7,500 7,500 5,000 4,800 7,200 7,200 4,300<br />
32oc 6,300 9,450 9,450 6,300 6,200 9,300 9,300 6,200<br />
48oc 8,100 12,150 12,150 8,100 6,750 10,800 10,800 6,750<br />
Multiplier for<br />
Structural I Panels 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0<br />
PANEL AXIAL STIFFNESS, EA (lb/ft of panel width)<br />
24/0 3,350,000 3,350,000 3,350,000 3,350,000 2,900,000 2,900,000 2,900,000 2,900,000<br />
24/16 3,800,000 3,800,000 3,800,000 3,800,000 2,900,000 2,900,000 2,900,000 2,900,000<br />
32/16 4,150,000 4,150,000 4,150,000 4,150,000 3,600,000 3,600,000 3,600,000 3,600,000<br />
40/20 5,000,000 5,000,000 5,000,000 5,000,000 4,500,000 4,500,000 4,500,000 4,500,000<br />
48/24 5,850,000 5,850,000 5,850,000 5,850,000 5,000,000 5,000,000 5,000,000 4,500,000<br />
16oc 4,500,000 4,500,000 4,500,000 4,500,000 4,200,000 4,200,000 4,200,000 4,200,000<br />
20oc 5,000,000 5,000,000 5,000,000 5,000,000 4,500,000 4,500,000 4,500,000 4,500,000<br />
24oc 5,850,000 5,850,000 5,850,000 5,850,000 5,000,000 5,000,000 5,000,000 4,500,000<br />
32oc 7,500,000 7,500,000 7,500,000 7,500,000 7,300,000 7,300,000 7,300,000 5,850,000<br />
48oc 8,200,000 8,200,000 8,200,000 8,200,000 7,300,000 7,300,000 7,300,000 7,300,000<br />
9<br />
M9: WOOD STRUCTURAL PANELS<br />
Multiplier for<br />
Structural I Panels 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0<br />
1. Strength axis is defined as the axis parallel to the face and back orientation of the flakes or the grain (veneer), which is generally the long panel direction, unless<br />
otherwise marked.<br />
<strong>American</strong> Forest & paper association
64 M9: WOOD STRUCTURAL PANELS<br />
Compression (F c A)<br />
Compression (Figure M9.2-3) capacities listed in<br />
Table M9.2-2 are based on testing according to the principles<br />
of ASTM D3501 Method B. Compressive properties<br />
are generally influenced by buckling; however, this effect<br />
was eliminated by restraining the edges of the specimens<br />
during testing. Compression capacity is given as F c A. F c is<br />
the reference compression stress of the material, and A is<br />
the area of the cross section. The units of F c A are pounds<br />
per foot of panel width.<br />
Shear Capacities<br />
Figure M9.2-3<br />
Structural Panel with<br />
Axial Compression<br />
Load in the Plane of<br />
the Panel<br />
Planar (Rolling) Shear (F s [Ib/Q])<br />
Shear-in-the-plane of the panel (rolling shear) capacities<br />
listed in Table M9.2-3 are based on testing according<br />
to the principles of ASTM D2718. Shear strength in the<br />
plane of the panel is the capacity to resist horizontal shear<br />
breaking loads when loads are applied or developed on opposite<br />
faces of the panel (Figure M9.2-4), as in flat panel<br />
bending. Planar shear capacity is given as F s [Ib/Q]. F s is<br />
the reference material stress, and Ib/Q is the panel crosssectional<br />
shear constant. The units of F s [Ib/Q] are pounds<br />
per foot of panel width.<br />
Figure M9.2-5 Through-the-Thickness<br />
Shear for <strong>Wood</strong><br />
Structural Panels<br />
Rigidity Through-the-Thickness (G v t v )<br />
Panel rigidities listed in Table M9.2-4 are based on<br />
testing according to the principles of ASTM D2719 Method<br />
C. Panel rigidity is the capacity to resist deformation<br />
under shear through the thickness stress (Figure M9.2-5).<br />
Rigidity is given as G v t v . G v is the reference modulus of<br />
rigidity, and t v is the effective panel thickness for shear.<br />
The units of G v t v are pounds per inch of panel depth (for<br />
vertical applications). Multiplication of G v t v by panel depth<br />
gives GA, used by designers for some applications.<br />
Through-the-Thickness Shear (F v t v )<br />
Through-the-thickness shear capacities listed in Table<br />
M9.2-4 are based on testing according to the principles of<br />
ASTM D2719 Method C. Allowable through the thickness<br />
shear is the capacity to resist horizontal shear breaking<br />
loads when loads are applied or developed on opposite<br />
edges of the panel (Figure M9.2-5), such as in an I-beam.<br />
Where additional support is not provided to prevent<br />
bucking, design capacities in Table M9.2-4 are limited to<br />
sections 2 ft or less in depth. Deeper sections may require<br />
additional reductions. F v is the reference stress of the<br />
material, and t v is the effective panel thickness for shear.<br />
The units of F v t v are pounds per inch of shear resisting<br />
panel length.<br />
Figure M9.2-4<br />
Planar (Rolling) Shear<br />
or Shear-in-the-Plane<br />
for <strong>Wood</strong> Structural<br />
Panels<br />
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
65<br />
Table M9.2-3<br />
<strong>Wood</strong> Structural Panel Planar (Rolling) Shear Capacities<br />
Stress Parallel to Strength Axis<br />
Stress Perpendicular to Strength Axis<br />
Span Plywood Plywood<br />
Rating 3-ply 4-ply 5-ply OSB 3-ply 4-ply 5-ply OSB<br />
PANEL SHEAR-IN-THE-PLANE, F s (Ib/Q) (lb/ft of panel width)<br />
24/0 155 155 170 130 275 375 130 130<br />
24/16 180 180 195 150 315 435 150 150<br />
32/16 200 200 215 165 345 480 165 165<br />
40/20 245 245 265 205 430 595 205 205<br />
48/24 300 300 325 250 525 725 250 250<br />
16oc 245 245 265 205 430 595 205 205<br />
20oc 245 245 265 205 430 595 205 205<br />
24oc 300 300 325 250 525 725 250 250<br />
32oc 360 360 390 300 630 870 300 300<br />
48oc 460 460 500 385 810 1,100 385 385<br />
Multiplier for<br />
Structural I Panels 1.4 1.4 1.4 1.0 1.4 1.4 1.0 1.0<br />
Table M9.2-4<br />
<strong>Wood</strong> Structural Panel Rigidity and Through-the-Thickness<br />
Shear Capacities<br />
Span<br />
Rating<br />
Stress Parallel to Strength Axis<br />
Plywood<br />
Stress Perpendicular to Strength Axis<br />
Plywood<br />
3-ply 4-ply 5-ply 1 OSB 3-ply 4-ply 5-ply 1<br />
PANEL RIGIDITY THROUGH-THE-THICKNESS, G v t v (lb/in. of panel depth)<br />
24/0 25,000 32,500 37,500 77,500 25,000 32,500 37,500 77,500<br />
24/16 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500<br />
32/16 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500<br />
40/20 28,500 37,000 43,000 88,500 28,500 37,000 43,000 88,500<br />
48/24 31,000 40,500 46,500 96,000 31,000 40,500 46,500 96,000<br />
16oc 27,000 35,000 40,500 83,500 27,000 35,000 40,500 83,500<br />
20oc 28,000 36,500 42,000 87,000 28,000 36,500 42,000 87,000<br />
24oc 30,000 39,000 45,000 93,000 30,000 39,000 45,000 93,000<br />
32oc 36,000 47,000 54,000 110,000 36,000 47,000 54,000 110,000<br />
48oc 50,500 65,500 76,000 155,000 50,500 65,500 76,000 155,000<br />
Multiplier for<br />
Structural I Panels 1.3 1.3 1.1 1.0 1.3 1.3 1.1 1.0<br />
PANEL THROUGH-THE-THICKNESS SHEAR, F v t v (lb/in. of shear-resisting panel length)<br />
24/0 53 69 80 155 53 69 80 155<br />
24/16 57 74 86 165 57 74 86 165<br />
32/16 62 81 93 180 62 81 93 180<br />
40/20 68 88 100 195 68 88 100 195<br />
48/24 75 98 115 220 75 98 115 220<br />
16oc 58 75 87 170 58 75 87 170<br />
20oc 67 87 100 195 67 87 100 195<br />
24oc 74 96 110 215 74 96 110 215<br />
32oc 80 105 120 230 80 105 120 230<br />
48oc 105 135 160 305 105 135 160 305<br />
Multiplier for<br />
Structural I Panels 1.3 1.3 1.1 1.0 1.3 1.3 1.1 1.0<br />
1. 5-ply applies to plywood with five or more layers. For 5-ply plywood with three layers, use G n t n values for 4-ply panels.<br />
OSB<br />
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M9: WOOD STRUCTURAL PANELS<br />
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66 M9: WOOD STRUCTURAL PANELS<br />
M9.3 Adjustment of Reference Design Values<br />
General<br />
Adjusted panel design capacities are determined by<br />
multiplying reference capacities, as given in Tables M9.2-<br />
1 through M9.2-4, by the adjustment factors in NDS 9.3.<br />
Some adjustment factors should be obtained from the<br />
manufacturer or other approved source. In the NDS Commentary,<br />
C9.3 provides additional information on typical<br />
adjustment factors.<br />
Tabulated capacities provided in this Chapter are<br />
suitable for reference end-use conditions. Reference<br />
end-use conditions are consistent with conditions typically<br />
associated with light-frame construction. For wood<br />
structural panels, these typical conditions involve the use<br />
of full-sized untreated panels in moderate temperature and<br />
moisture exposures.<br />
Appropriate adjustment factors are provided for applications<br />
in which the conditions of use are inconsistent<br />
with reference conditions. In addition to temperature and<br />
moisture, this includes consideration of panel treatment<br />
and size effects.<br />
NDS Table 9.3.1 lists applicability of adjustment factors<br />
for wood structural panels. Table M9.3-1 shows the<br />
applicability of adjustment factors for wood structural<br />
panels in a slightly different format for the designer.<br />
Table M9.3-1<br />
Applicability of Adjustment Factors for <strong>Wood</strong> Structural Panels<br />
Allowable Stress Design<br />
F b S′ = F b S C D C M C t C G C s<br />
F t A′ = F t A C D C M C t C G C s<br />
F v t v ′ = F v t v C D C M C t C G<br />
F s (Ib/Q)′ = F s (Ib/Q) C D C M C t C G<br />
F c A′ = F c A C D C M C t C G<br />
EI′ = EI C M C t C G<br />
EA′ = EA C M C t C G<br />
G v t v ′ = G v t v C M C t C G<br />
F c⊥ ′ = F c⊥ C M C t C G<br />
Bending Member Example<br />
For non-Structural I grade wood structural panels,<br />
greater than 24" in width, loaded in bending, and used<br />
in a normal building environment (meeting the reference<br />
conditions of NDS 2.3 and 9.3), the adjusted design values<br />
reduce to:<br />
For <strong>ASD</strong>:<br />
F b S′ = F b S C D<br />
EI′ = EI<br />
For <strong>LRFD</strong>:<br />
F b S′ = F b S K F φ b λ<br />
EI′ = EI<br />
Load and Resistance Factor Design<br />
F b S′ = F b S C M C t C G C s K F φ b λ<br />
F t A′ = F t A C M C t C G C s K F φ t λ<br />
F v t v ′ = F v t v C M C t C G K F φ v λ<br />
F s (Ib/Q)′ = F s (Ib/Q) C M C t C G K F φ v λ<br />
F c A′ = F c A C M C t C G K F φ c λ<br />
EI′ = EI C M C t C G<br />
EA′ = EA C M C t C G<br />
G v t v ′ = G v t v C M C t C G<br />
F c⊥ ′ = F c⊥ C M C t C G K F φ c λ<br />
Axially Loaded Member Example<br />
For non-Structural I grade wood structural panels,<br />
greater than 24" in width, axially loaded, and used in a<br />
normal building environment (meeting the reference conditions<br />
of NDS 2.3 and 4.3) designed to resist tension or<br />
compression loads, the adjusted tension or compression<br />
design values reduce to:<br />
For <strong>ASD</strong>:<br />
F c A′ = F c A C D<br />
F t A′ = F t A C D<br />
EA′ = EA<br />
For <strong>LRFD</strong>:<br />
F c A′ = F c A K F φ c λ<br />
F t A′ = F t A K F φ t λ<br />
EA′ = EA<br />
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Preservative Treatment<br />
Capacities given in Tables M9.2-1 through M9.2-4 apply<br />
without adjustment to plywood pressure-impregnated<br />
with preservatives and redried in accordance with <strong>American</strong><br />
<strong>Wood</strong>-Preservers’ Association (AWPA) Specification<br />
C-9 or Specification C-22. However, due to the absence<br />
of applicable treating industry standards, OSB and COM-<br />
PLY panels are not currently recommended for applications<br />
requiring pressure-preservative treating.<br />
Fire Retardant Treatment<br />
The information provided in this Chapter does not<br />
apply to fire-retardant-treated panels. All capacities and<br />
end-use conditions for fire-retardant-treated panels shall be<br />
in accordance with the recommendations of the company<br />
providing the treating and redrying service.<br />
M9.4 Special Design Considerations<br />
Panel Edge Support<br />
Panel Spacing<br />
For certain span ratings, the maximum recommended<br />
roof span for sheathing panels is dependent upon panel<br />
edge support. Although edge support may be provided<br />
by lumber blocking, panel clips are typically used when<br />
edge support is required. Table M9.4-1 summarizes the<br />
relationship between panel edge support and maximum<br />
recommended spans.<br />
Table M9.4-1<br />
Sheathing<br />
Span Rating<br />
Panel Edge Support<br />
Maximum Recommended Span (in.)<br />
With<br />
Edge Support<br />
Without<br />
Edge Support<br />
24/0 24 20 1<br />
24/16 24 24<br />
32/16 32 28<br />
40/20 40 32<br />
48/24 48 36<br />
1. 20 in. for 3/8-in. and 7/16-in. panels, 24 in. for 15/32-in. and 1/2-in.<br />
panels.<br />
Long-Term Loading<br />
<strong>Wood</strong>-based panels under constant load will creep<br />
(deflection will increase) over time. For typical construction<br />
applications, panels are not normally under constant<br />
load and, accordingly, creep need not be considered in<br />
design. When panels will sustain permanent loads which<br />
will stress the product to one-half or more of its design<br />
capacity, allowance should be made for creep. Appropriate<br />
adjustments should be obtained from the manufacturer or<br />
an approved source.<br />
<strong>Wood</strong>-based panel products expand and contract<br />
slightly as a natural response to changes in panel moisture<br />
content. To provide for in-plane dimensional changes,<br />
panels should be installed with a 1/8" spacing at all panel<br />
end and edge joints. A standard 10d box nail may be used<br />
to check panel edge and panel end spacing.<br />
Minimum Nailing<br />
Minimum nailing for wood structural panel applications<br />
is shown in Table M9.4-2.<br />
9<br />
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Table M9.4-2<br />
Minimum Nailing for <strong>Wood</strong> Structural Panel Applications<br />
Nail Spacing (in.)<br />
Recommended<br />
Panel Intermediate<br />
Application Nail Size & Type<br />
Edges Supports<br />
Single Floor–Glue-nailed installation 5<br />
Ring- or screw-shank<br />
16, 20, 24 oc, 3/4-in. thick or less 6d 1 12 12<br />
24 oc, 7/8-in. or 1-in. thick 8d 1 6 12<br />
32, 48 oc, 32-in. span (c-c) 8d 1 6 12<br />
48 oc, 48-in. span (c-c) 8d 2 6 6<br />
Single Floor–Nailed-only installation 5<br />
Ring- or screw-shank<br />
16, 20, 24 oc, 3/4-in. thick or less 6d 6 12<br />
24 oc, 7/8-in. or 1-in. thick 8d 6 12<br />
32, 48 oc, 32-in. span 8d 2 6 12<br />
48 oc, 48-in. span 8d 2 6 6<br />
Sheathing–Subflooring 3<br />
Common smooth, ring- or screw-shank<br />
7/16-in. to 1/2-in. thick 6d 6 12<br />
7/8-in. thick or less 8d 6 12<br />
Thicker panels 10d 6 6<br />
Sheathing–Wall sheathing Common smooth, ring- or screw-shank or galvanized box 3<br />
1/2-in. thick or less 6d 6 12<br />
Over 1/2-in. thick 8d 6 12<br />
Sheathing–Roof sheathing Common smooth, ring- or screw-shank 3<br />
5/16-in. to 1-in. thick 8d 6 12 4<br />
Thicker panels 8d ring- or screw-shank 6 12 4<br />
or 10d common smooth<br />
1. 8d common nails may be substituted if ring- or screw-shank nails are not available.<br />
2. 10d ring-shank, screw-shank, or common nails may be substituted if supports are well seasoned.<br />
3. Other code-approved fasteners may be used.<br />
4. For spans 48 in. or greater, space nails 6 in. at all supports.<br />
5. Where required by the authority having jurisdiction, increased nailing schedules may be required.<br />
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69<br />
M10:<br />
MECHANICAL<br />
CONNECTIONS<br />
M10.1 General 70<br />
M10.2 Reference Design Values 71<br />
M10.3 Design Adjustment Factors 71<br />
M10.4 Typical Connection Details 72<br />
M10.5 Pre-Engineered Metal Connectors 80<br />
10<br />
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70 M10: MECHANICAL CONNECTIONS<br />
M10.1 General<br />
This Chapter covers design of connections between<br />
wood members using metal fasteners. Several common<br />
connection types are outlined below.<br />
Dowel-Type (Nails, Bolts, Screws,<br />
Pins)<br />
These connectors rely on metal-to-wood bearing for<br />
transfer of lateral loads and on friction or mechanical<br />
interfaces for transfer of axial (withdrawal) loads. They<br />
are commonly available in a wide range of diameters and<br />
lengths. More information is provided in Chapter M11.<br />
Split Rings and Shear Plates<br />
These connectors rely on their geometry to provide<br />
larger metal-to-wood bearing areas per connector. Both<br />
are installed into precut grooves or daps in the members.<br />
More information is provided in Chapter M12.<br />
Timber Rivets<br />
Timber rivets are a dowel-type connection, however,<br />
because the ultimate load capacity of such connections<br />
are limited by rivet bending and localized crushing of<br />
wood at the rivets or by the tension or shear strength of the<br />
wood at the perimeter of the rivet group, a specific design<br />
procedure is required. Timber rivet design loads are based<br />
on the lower of the maximum rivet bending load and the<br />
maximum load based on wood strength. Chapter M13<br />
contains more information on timber rivet design.<br />
Structural Framing Connections<br />
Structural framing connections provide a single-piece<br />
connection between two framing members. They generally<br />
consist of bent or welded steel, carrying load from<br />
the supported member (through direct bearing) into the<br />
supporting member (by hanger flange bearing, fastener<br />
shear, or a combination of the two). Structural framing<br />
connections are proprietary connectors and are discussed<br />
in more detail in M10.4.<br />
Other Connectors<br />
Just as the number of possible building geometries<br />
is limitless, so too is the number of possible connection<br />
geometries. In addition to providing custom fabrication<br />
of connectors to meet virtually any geometry that can be<br />
designed, metal connector manufacturers have several<br />
categories of connectors that do not fit the categories<br />
above, including:<br />
• framing anchors<br />
• holddown devices<br />
• straps and ties<br />
These connectors are also generally proprietary connectors.<br />
See the manufacturer’s literature or M10.4 for<br />
more information regarding design.<br />
Connections are designed so that no applicable capacity<br />
is exceeded under loads. Strength criteria include<br />
lateral or withdrawal capacity of the connection, and<br />
tension or shear in the metal components. Some types of<br />
connections also include compression perpendicular to<br />
grain as a design criteria.<br />
Users should note that design of connections may also<br />
be controlled by serviceability limitations. These limitations<br />
are product specific and are discussed in specific<br />
product chapters.<br />
Stresses in Members at<br />
Connections<br />
Local stresses in connections using multiple fasteners<br />
can be evaluated in accordance with NDS Appendix E.<br />
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M10.2 Reference Design Values<br />
Reference design values for mechanical connections<br />
are provided in various sources. The NDS contains reference<br />
design values for dowel-type connections such as<br />
nails, bolts, lag screws, wood screws, split rings, shear<br />
plates, drift bolts, drift pins, and timber rivets.<br />
Pre-engineered metal connectors are proprietary and<br />
reference design values are provided in code evaluation<br />
reports. More information on their use is provided in<br />
M10.5.<br />
Metal connector plates are proprietary connectors for<br />
trusses, and reference design values are provided in code<br />
evaluation reports.<br />
Staples and many pneumatic fasteners are proprietary,<br />
and reference design values are provided in code evaluation<br />
reports.<br />
M10.3 Design Adjustment Factors<br />
To generate connection design capacities, reference<br />
design values for connections are multiplied by adjustment<br />
factors per NDS 10.3. Applicable adjustment factors<br />
for connections are defined in NDS Table 10.3.1. Table<br />
M10.3-1 shows the applicability of adjustment factors<br />
for connections in a slightly different format for the designer.<br />
Table M10.3-1 Applicability of Adjustment Factors for Mechanical Connections 1<br />
Allowable Stress Design<br />
The following connection product chapters contain<br />
examples of the application of adjustment factors to reference<br />
design values:<br />
Lateral Loads<br />
Load and Resistance Factor Design<br />
Dowel-Type Fasteners Z′ = Z C D C M C t C g C ∆ C eg C di C tn Z′ = Z C M C t C g C ∆ C eg C di C tn K F φ z λ<br />
Split Ring and Shear<br />
Plate Connectors<br />
Timber Rivets<br />
P′ = P C D C M C t C g C ∆ C d C st P′ = P C M C t C g C ∆ C d C st K F φ z λ<br />
Q′ = Q C D C M C t C g C ∆ C d Q′ = Q C M C t C g C ∆ C d K F φ z λ<br />
P′ = P C D C M C t C st P′ = P C M C t C st K F φ z λ<br />
Q′ = Q C D C M C t C ∆ C st Q′ = Q C M C t C ∆ C st K F φ z λ<br />
Metal Plate Connectors Z′ = Z C D C M C t Z′ = Z C M C t K F φ z λ<br />
Spike Grids Z′ = Z C D C M C t C ∆ Z′ = Z C M C t C ∆ K F φ z λ<br />
Nails, Spikes, Lag Screws,<br />
<strong>Wood</strong> Screws, and Drift Pins<br />
Withdrawal Loads<br />
W′ = W C D C M C t C eg C tn Z′ = Z C M C t C eg C tn K F φ z λ<br />
1. See NDS Table 10.3.1 footnotes for additional guidance on application of adjustment factors for mechanical connections.<br />
10<br />
M10: MECHANICAL CONNECTIONS<br />
Chapter M11 – dowel-type fasteners,<br />
Chapter M12 – split ring and shear plate connectors,<br />
Chapter M13 – timber rivets.<br />
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72 M10: MECHANICAL CONNECTIONS<br />
M10.4 Typical Connection Details<br />
General Concepts of Well-<br />
Designed Connections<br />
Connections must obviously provide the structural<br />
strength necessary to transfer loads. Well-designed connections<br />
hold the wood members in such a manner that<br />
shrinkage/swelling cycles do not induce splitting across<br />
the grain. Well-designed connections also minimize regions<br />
that might collect moisture – providing adequate<br />
clearance for air movement to keep the wood dry. Finally,<br />
well-designed connections minimize the potential for tension<br />
perpendicular to grain stresses – either under design<br />
conditions or under unusual loading conditions.<br />
The following connection details (courtesy of the Canadian<br />
<strong>Wood</strong> <strong>Council</strong>) are organized into nine groups:<br />
1. Beam to concrete or masonry wall connections<br />
2. Beam to column connections<br />
3. Column to base connections<br />
4. Beam to beam connections<br />
5. Cantilever beam connections<br />
6. Arch peak connections<br />
7. Arch base to support<br />
8. Moment splice<br />
9. Problem connections<br />
1. Beam on shelf in wall. The bearing plate distributes<br />
the load and keeps the beam from direct contact with the<br />
concrete. Steel angles provide uplift resistance and can<br />
also provide some lateral resistance. The end of the beam<br />
should not be in direct contact with the concrete.<br />
2. Similar to detail 1 with a steel bearing plate only under<br />
the beam.<br />
Many of the detail groups begin with a brief discussion<br />
of the design challenges pertinent to the specific type<br />
of connection. Focusing on the key design concepts of a<br />
broad class of connections often leads to insights regarding<br />
a specific detail of interest.<br />
Group 1. Beam to Concrete or Masonry Wall<br />
Connections<br />
Design concepts. Concrete is porous and “wicks”<br />
moisture. Good detailing never permits wood to be in<br />
direct contact with concrete.<br />
3. Similar to detail 1 with slotted holes to accommodate<br />
slight lateral movement of the beam under load. This detail<br />
is more commonly used when the beam is sloped, rather<br />
than flat.<br />
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73<br />
Group 2. Beam to Column Connections<br />
Design concepts. All connections in the group must<br />
hold the beam in place on top of the column. Shear transfer<br />
is reasonably easy to achieve. Some connections must also<br />
resist some beam uplift. Finally, for cases in which the<br />
beam is spliced, rather than continuous over the column,<br />
transfer of forces across the splice may be required.<br />
6. Custom welded column caps can be designed to transfer<br />
shear, uplift, and splice forces. Note design variations to<br />
provide sufficient bearing area for each of the beams and<br />
differing plate widths to accommodate differences between<br />
the column and the beam widths.<br />
4. Simple steel dowel for shear transfer.<br />
7. Combinations of steel angles and straps, bolted and<br />
screwed, to transfer forces.<br />
5. Concealed connection in which a steel plate is inserted<br />
into a kerf in both the beam and the column. Transverse<br />
pins or bolts complete the connection.<br />
10<br />
8. A very common connection – beam seat welded to the<br />
top of a steel column.<br />
M10: MECHANICAL CONNECTIONS<br />
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74 M10: MECHANICAL CONNECTIONS<br />
9. When both beams and columns are continuous and the<br />
connection must remain in-plane, either the beam or the<br />
column must be spliced at the connection. In this detail the<br />
column continuity is maintained. Optional shear plates may<br />
be used to transfer higher loads. Note that, unless the bolt<br />
heads are completely recessed into the back of the bracket,<br />
the beam end will likely require slotting. In a building with<br />
many bays, it may be difficult to maintain dimensions in<br />
the beam direction when using this connection.<br />
11A. Similar to details 1 and 2.<br />
11B. Alternate to detail 11A.<br />
Group 3. Column to Base Connections<br />
Design concepts. Since this is the bottom of the structure,<br />
it is conceivable that moisture from some source<br />
might run down the column. Experience has shown that<br />
base plate details in which a steel “shoe” is present can<br />
collect moisture that leads to decay in the column.<br />
12. Similar to detail 3.<br />
10. Similar to detail 4, with a bearing plate added.<br />
Group 4. Beam to Beam Connections<br />
Design concepts. Many variations of this type of connection<br />
are possible. When all members are flat and their<br />
tops are flush, the connection is fairly straightforward.<br />
Slopes and skews require special attention to fabrication<br />
dimensions – well-designed connections provide adequate<br />
clearance to insert bolts or other connectors and also provide<br />
room to grip and tighten with a wrench. Especially for<br />
sloped members, special attention is required to visualize<br />
the stresses induced as the members deflect under load<br />
– some connections will induce large perpendicular to<br />
grain stresses in this mode.<br />
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75<br />
13. Bucket-style welded bracket at a “cross” junction. The<br />
top of the support beam is sometimes dapped to accommodate<br />
the thickness of the steel.<br />
suspended beam, permitting plugging of the holes after the<br />
pin is installed. Note that the kerf in the suspended beam<br />
must accommodate not only the width of the steel plate,<br />
but also the increased width at the fillet welds.<br />
14. Face-mounted hangers are commonly used in beam to<br />
beam connections. In a “cross” junction special attention<br />
is required to fastener penetration length into the carrying<br />
beam (to avoid interference from other side).<br />
17. Similar to detail 13, with somewhat lower load<br />
capacity.<br />
18. Clip angle to connect crossing beam.<br />
15. Deep members may be supported by fairly shallow<br />
hangers – in this case, through-bolted with shear plates.<br />
Clip angles are used to prevent rotation of the top of the<br />
suspended beam. Note that the clip angles are not connected<br />
to the suspended beam – doing so would restrain a<br />
deep beam from its natural across-the-grain shrinking and<br />
swelling cycles and would lead to splits.<br />
19. Special detail to connect the ridge purlin to sloped<br />
members or to the peak of arch members.<br />
10<br />
M10: MECHANICAL CONNECTIONS<br />
16. Concealed connections similar to detail 5. The suspended<br />
beam may be dapped on the bottom for a flush<br />
connection. The pin may be slightly narrower than the<br />
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76 M10: MECHANICAL CONNECTIONS<br />
20A. Similar to detail 19, but with the segments of the<br />
ridge purlin set flush with the other framing.<br />
23. Similar to detail 22, with added shear plate.<br />
20B. Alternate to detail 20A.<br />
24. Similar to detail 22 for low slope arches. Side plates<br />
replace the threaded rod.<br />
Group 5. Cantilever Beam Connections<br />
21. Hinge connector transfers load without need to slope<br />
cut member ends. Beams are often dapped top and bottom<br />
for a flush fit.<br />
Group 6. Arch Peak Connections<br />
Group 7. Arch Base to Support<br />
Design concepts. Arches transmit thrust into the supporting<br />
structure. The foundation may be designed to resist<br />
this thrust or tie rods may be used. The base detail should<br />
be designed to accommodate the amount of rotation anticipated<br />
in the arch base under various loading conditions.<br />
Elastomeric bearing pads can assist somewhat in distributing<br />
stresses. As noted earlier, the connection should be<br />
designed to minimize any perpendicular to grain stresses<br />
during the deformation of the structure under load.<br />
25. Welded shoe transmits thrust from arch to support.<br />
Note that inside edge of shoe is left open to prevent collection<br />
of moisture.<br />
22. Steep arches connected with a rod and shear plates.<br />
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26. Arch base fastened directly to a steel tie beam in a<br />
shoe-type connection.<br />
Group 8. Moment Splice<br />
Design concepts. Moment splices must transmit axial<br />
tension, axial compression, and shear. They must serve<br />
these functions in an area of the structure where structural<br />
movement may be significant – thus, they must not introduce<br />
cross-grain forces if they are to function properly.<br />
29. Separate pieces of steel each provide a specific function.<br />
Top and bottom plate transfer axial force, pressure<br />
plates transfer direct thrust, and shear plates transmit<br />
shear.<br />
27. Similar to detail 25. This more rigid connection is<br />
suitable for spans where arch rotation at the base is small<br />
enough to not require the rotational movement permitted<br />
in detail 25. Note that, although the shoe is “boxed” a<br />
weep slot is provided at the inside face.<br />
30. Similar to detail 29. Connectors on side faces may be<br />
easier to install, but forces are higher because moment arm<br />
between steel straps is less than in detail 29.<br />
10<br />
28. For very long spans or other cases where large rotations<br />
must be accommodated, a true hinge connection<br />
may be required.<br />
Group 9. Problem Connections<br />
Hidden column base. It is sometimes preferable architecturally<br />
to conceal the connection at the base of the<br />
column. In any case it is crucial to detail this connection<br />
to minimize decay potential.<br />
M10: MECHANICAL CONNECTIONS<br />
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31A. Similar to detail 11, but with floor slab poured over<br />
the top of the connection. THIS WILL CAUSE DECAY<br />
AND IS NOT A RECOMMENDED DETAIL!<br />
32B. As an alternative to detail 32A, smaller plates will<br />
transmit forces, but they do not restrain the wood from its<br />
natural movements.<br />
31B. Alternate to detail 31A.<br />
Notched beam bearing. Depth limitations sometimes<br />
cause detailing difficulties at the beam supports. A simple<br />
solution is to notch the beam at the bearing. This induces<br />
large tension perpendicular to grain stresses and leads to<br />
splitting of the beam at the root of the notch.<br />
33A. Notching a beam at its bearing may cause splits.<br />
THIS DETAIL IS NOT RECOMMENDED!<br />
Full-depth side plates. It is sometimes easier to fabricate<br />
connections for deep beams from large steel plates<br />
rather than having to keep track of more pieces. Lack of<br />
attention to wood’s dimensional changes as it “breathes”<br />
may lead to splits.<br />
32A. Full-depth side plates may appear to be a good connection<br />
option. Unfortunately, the side plates will remain<br />
fastened while the wood shrinks over the first heating<br />
season. Since it is restrained by the side plates, the beam<br />
may split. THIS DETAIL IS NOT RECOMMENDED!<br />
33B. Alternate to detail 33A.<br />
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34A. This sloped bearing with a beam that is not fully<br />
supported may also split under load. THIS DETAIL IS<br />
NOT RECOMMENDED!<br />
35B. As an alternative to detail 35A, the plates may be<br />
extended and the connection made to the upper half of<br />
the beam.<br />
34B. Alternate to detail 34A.<br />
Hanger to side of beam. See full-depth side plates<br />
discussion.<br />
36A. Deep beam hangers that have fasteners installed<br />
in the side plates toward the top of the supported beam<br />
may promote splits at the fastener group should the wood<br />
member shrink and lift from the bottom of the beam hanger<br />
because of the support provided by the fastener group.<br />
THIS DETAIL IS NOT RECOMMENDED!<br />
Hanging to underside of beam. Sometimes it is advantageous<br />
to hang a load from the underside of a beam.<br />
This is acceptable as long as the hanger is fastened to the<br />
upper half of the beam. Fastening to the lower half of the<br />
beam may induce splits.<br />
35A. Connecting a hanger to the lower half of a beam that<br />
pulls downward may cause splits. THIS DETAIL IS NOT<br />
RECOMMENDED!<br />
36B. Alternate to detail 36A.<br />
10<br />
M10: MECHANICAL CONNECTIONS<br />
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80 M10: MECHANICAL CONNECTIONS<br />
M10.5 Pre-Engineered Metal Connectors<br />
Product Information<br />
Pre-engineered metal connectors for wood construction<br />
are commonly used in all types of wood construction.<br />
There are numerous reasons for their widespread use.<br />
Connectors often make wood members easier and faster<br />
to install. They increase the safety of wood construction,<br />
not only from normal loads, but also from natural disasters<br />
such as earthquakes and high winds. Connectors make<br />
wood structures easier to design by providing simpler<br />
connections of known load capacity. They also allow for<br />
the use of more cost-effective engineered wood members<br />
by providing the higher capacity connections often required<br />
by the use of such members. In certain locations,<br />
model building codes specifically require connectors or<br />
hangers.<br />
Metal connectors are usually manufactured by stamping<br />
sheets or strips of steel, although some heavy hangers<br />
are welded together. Different thicknesses and grades of<br />
steel are used, depending on the required capacity of the<br />
connector.<br />
Some metal connectors are produced as proprietary<br />
products which are covered by evaluation reports from one<br />
or all of the model building codes. Such reports should<br />
be consulted for current design information, while the<br />
manufacturer’s literature can be consulted for additional<br />
design information and detailed installation instructions.<br />
Common Uses<br />
Pre-engineered metal connectors for wood construction<br />
are used throughout the world. Connectors are used<br />
to resist vertical dead, live, and snow loads; uplift loads<br />
from wind; and lateral loads from ground motion or wind.<br />
Almost any type of wood member may be fastened to<br />
another using a connector. Connectors may also be used<br />
to fasten wood to other materials, such as concrete, masonry,<br />
or steel.<br />
Availability<br />
Connectors are manufactured in varying load capacities,<br />
sizes, and configurations to fit a wide range of<br />
applications. A variety of connectors are widely available<br />
through lumber suppliers.<br />
Because of the wide variety of available connectors, a<br />
generic design document such as this must be limited in its<br />
scope for simplicity’s sake. Design values for specific connectors<br />
are available from the connector manufacturer.<br />
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Types of Connectors<br />
There are many different types of connectors, due to<br />
the many different applications in which connectors may<br />
be used. The following sections list the most common<br />
types of connectors.<br />
Face Mount Joist Hangers<br />
Face mount joist hangers install on the face of the<br />
supporting member, and rely on the shear capacity of the<br />
nails to provide holding power. Although referred to as<br />
joist hangers, these connectors may support other horizontal<br />
members subject to vertical loads, such as beams<br />
or purlins.<br />
Top Flange Joist Hangers<br />
Top flange joist, beam, and purlin hangers rely on bearing<br />
of the top flange onto the top of the supporting member,<br />
along with the shear capacity of any fasteners that are<br />
present in the face. Although referred to as joist hangers,<br />
these connectors may support other horizontal members<br />
subject to vertical loads, such as beams or purlins.<br />
Bent-style Joist, Beam,<br />
and Purlin Hanger*<br />
top Flange<br />
i-joist Hanger*<br />
Face Mount<br />
Joist Hanger<br />
Heavy Face Mount<br />
Joist Hanger<br />
10<br />
S tr ong- Tie<br />
SIMPSON<br />
Slope- and Skew-<br />
Adjustable Joist Hanger<br />
Face Mount<br />
I-Joist Hanger*<br />
Welded-type Purlin,<br />
Beam, and Joist Hanger*<br />
Heavy Welded Beam<br />
Hanger (Saddle Type)<br />
M10: MECHANICAL CONNECTIONS<br />
* Hangers should be capable of providing lateral support to the top flange of the joist. This is usually accomplished by a hanger flange that extends the full depth of<br />
the joist. At a minimum, hanger support should extend to at least mid-height of a joist used with web stiffeners. Some connector manufacturers have developed<br />
hangers specifically for use with wood I-joists that provide full lateral support without the use of web stiffeners.<br />
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Adjustable Style Hanger<br />
Adjustable style joist and truss hangers have straps<br />
which can be either fastened to the face of a supporting<br />
member, similar to a face mount hanger, or wrapped over<br />
the top of a supporting member, similar to a top flange<br />
hanger.<br />
Seismic and Hurricane Ties<br />
Seismic and hurricane ties are typically used to connect<br />
two members that are oriented 90º from each other. These<br />
ties resist forces through the shear capacity of the nails in<br />
the members. These connectors may provide resistance in<br />
three dimensions.<br />
Adjustable Style Truss Hangers<br />
Seismic and Hurricane Ties<br />
Connecting Roof Framing to Top Plates<br />
Flat Straps<br />
Flat straps rely on the shear capacity of the nails in the<br />
wood members to transfer load.<br />
Holddowns and Tension Ties<br />
Holddowns and tension ties usually bolt to concrete<br />
or masonry, and connect wood members to the concrete<br />
or masonry through the shear resistance of either nails,<br />
screws, or bolts. They may also be used to connect two<br />
wood members together.<br />
Strap Used to<br />
Transfer Uplift Forces<br />
strap Used to<br />
Transfer Lateral Forces<br />
Holddown<br />
tension Tie<br />
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Embedded Type Anchors<br />
Embedded anchors connect a wood member to concrete<br />
or masonry. One end of the connector embeds in the<br />
concrete or masonry, and the other end connects to the<br />
wood through the shear resistance of the nails or bolts.<br />
• type of fasteners to be used<br />
• corrosion resistance desired<br />
• appearance desired<br />
Once the listed information is known, proper selection<br />
is facilitated through the use of manufacturer’s literature,<br />
code evaluation reports, and software available from connector<br />
manufacturers.<br />
This <strong>Manual</strong> provides guidance for specifying preengineered<br />
metal connectors to satisfy specific design<br />
criteria for a given application.<br />
Embedded Truss Anchor<br />
Embedded Nailed<br />
Holddown Strap<br />
Connection Details<br />
Connections, including pre-engineered metal connections,<br />
must provide the structural strength necessary<br />
to transfer loads. Well-designed connections hold wood<br />
members in such a manner that shrinkage/swelling cycles<br />
do not induce splitting across the grain. Well-designed connections<br />
also minimize collection of moisture – providing<br />
adequate clearance for air movement to keep the wood dry.<br />
Finally, well-designed connections minimize the potential<br />
for tension perpendicular to grain stresses – either under<br />
design conditions or under unusual loading conditions.<br />
Section M10.4 contains general concepts of well designed<br />
connections, including over 40 details showing acceptable<br />
and unacceptable practice.<br />
Product Selection<br />
Purlin Anchor<br />
Proper choice of connectors is required to optimize<br />
performance and economics. The selection of a connector<br />
will depend on several variables. These include the<br />
following:<br />
Other Considerations<br />
With proper selection and installation, structural connectors<br />
will perform as they were designed. However, proper<br />
selection and installation involves a variety of items that<br />
both the designer and the installer must consider including<br />
the general topics of: the wood members being connected;<br />
the fasteners used; and the connectors themselves. These<br />
items are discussed in the following sections. This <strong>Manual</strong><br />
does not purport to address these topics in an all-inclusive<br />
manner – it is merely an attempt to alert designers to the<br />
importance of selection and installation details for achieving<br />
the published capacity of the connector.<br />
<strong>Wood</strong> Members<br />
The wood members being connected have an impact<br />
on the capacity of the connection. The following are important<br />
items regarding the wood members themselves:<br />
10<br />
M10: MECHANICAL CONNECTIONS<br />
• capacity required<br />
• size and type of members being connected<br />
• species of wood being connected<br />
• slope and/or skew of member<br />
• connector type preference<br />
• The species of wood must be the same as that for which<br />
the connector was rated by the manufacturer. Manufacturers<br />
test and publish allowable design values only for<br />
certain species of wood. For other species, consult with<br />
the connector manufacturer.<br />
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• The wood must not split when the fastener is installed.<br />
A fastener that splits the wood will not take the design<br />
load. If wood tends to split, consider pre-boring holes<br />
using a diameter not exceeding 3/4 of the nail diameter.<br />
Pre-boring requirements for screws and bolts are provided<br />
in the NDS.<br />
• <strong>Wood</strong> can shrink and expand as it loses and gains moisture.<br />
Most connectors are manufactured to fit common<br />
dry lumber dimensions. Other dimensions may be available<br />
from the manufacturer.<br />
• Where built-up lumber (multiple members) is installed<br />
in a connector, the members must be fastened together<br />
prior to installation of the connector so that the members<br />
act as a single unit.<br />
• The dimensions of the supporting member must be<br />
sufficient to receive the specified fasteners. Most connectors<br />
are rated based on full penetration of all specified<br />
fasteners. Refer to the connector manufacturer for other<br />
situations.<br />
• Bearing capacity of the joist or beam should also be<br />
evaluated to ensure adequate capacity.<br />
Fasteners<br />
Most wood connectors rely on the fasteners to transfer<br />
the load from one member to the other. Therefore, the<br />
choice and installation of the fasteners is critical to the<br />
performance of the connector.<br />
The following are important items regarding the fasteners<br />
used in the connector:<br />
Connectors<br />
Finally, the condition of the connector itself is critical<br />
to how it will perform. The following are important items<br />
regarding the connector itself:<br />
• Connectors may not be modified in the field unless<br />
noted by the manufacturer. Bending steel in the field<br />
may cause fractures at the bend line, and fractured steel<br />
will not carry the rated load.<br />
• Modified connectors may be available from the manufacturer.<br />
Not all modifications are tested by all manufacturers.<br />
Contact the manufacturer to verify loads on<br />
modified connectors.<br />
• In general, all holes in connectors should be filled with<br />
the nails specified by the manufacturer. Contact the<br />
manufacturer regarding optional nail holes and optional<br />
loads.<br />
• Different environments can cause corrosion of steel<br />
connectors. Always evaluate the environment where<br />
the connector will be installed. Connectors are available<br />
with differing corrosion resistances. Contact the<br />
manufacturer for availability. Fasteners must be at least<br />
the same corrosion resistance as that chosen for the<br />
connector.<br />
• All fasteners specified by the manufacturer must be<br />
installed to achieve the published value.<br />
• The size of fastener specified by the manufacturer must<br />
be installed. Most manufacturers specify common nails,<br />
unless otherwise noted.<br />
• The fastener must have at least the same corrosion<br />
resistance as the connector.<br />
• Bolts must generally be structural quality bolts, equal<br />
to or better than ANSI/ASME Standard B18.2.1.<br />
• Bolt holes must be a minimum of 1/32" and a maximum<br />
of 1/16" larger than the bolt diameter.<br />
• Fasteners must be installed prior to loading the connection.<br />
• Pneumatic or powder-actuated fasteners may deflect and<br />
injure the operator or others. Nail guns may be used to<br />
install connectors, provided the correct quantity and type<br />
of nails are properly installed in the manufacturer’s nail<br />
holes. Guns with nail hole-locating mechanisms should<br />
be used. Follow the nail gun manufacturer’s instructions<br />
and use the appropriate safety equipment.<br />
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M11: DOWEL-<br />
TYPE FASTENERS<br />
M11.1 General 86<br />
M11.2 Reference Withdrawal Design Values 86<br />
M11.3 Reference Lateral Design Values 86<br />
M11.4 Combined Lateral and Withdrawal<br />
Loads 86<br />
M11.5 Adjustment of Reference<br />
Design Values 87<br />
M11.6 Multiple Fasteners 87<br />
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86 M11: DOWEL-TYPE FASTENERS<br />
M11.1 General<br />
This Chapter covers design of connections between<br />
wood members using metal dowel-type (nails, bolts, lag<br />
screws, wood screws, drift pins) fasteners.<br />
These connectors rely on metal-to-wood bearing<br />
for transfer of lateral loads and on friction or mechanical<br />
interfaces for transfer of axial (withdrawal) loads. They<br />
are commonly available in a wide range of diameters and<br />
lengths.<br />
M11.2 Reference Withdrawal Design Values<br />
The basic design equation for dowel-type fasteners<br />
under withdrawal loads is:<br />
W′p ≥ R W<br />
where:<br />
W′ = adjusted withdrawal design value<br />
R W = axial (withdrawal) force<br />
p = depth of fastener penetration into<br />
wood member<br />
Reference withdrawal design values are tabulated in<br />
NDS Chapter 11.<br />
M11.3 Reference Lateral Design Values<br />
The basic equation for design of dowel-type fasteners<br />
under lateral load is:<br />
Z′ ≥ R Z<br />
where:<br />
Z′ = adjusted lateral design value<br />
R Z = lateral force<br />
Reference lateral design values are tabulated in NDS<br />
Chapter 11.<br />
M11.4 Combined Lateral and Withdrawal Loads<br />
Lag screws, wood screws, nails, and spikes resisting<br />
combined lateral and withdrawal loads shall be designed<br />
in accordance with NDS 11.4.<br />
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M11.5 Adjustment of Reference Design Values<br />
Dowel-type connections must be designed by applying<br />
all applicable adjustment factors to the reference<br />
withdrawal design value or reference lateral design value<br />
for the connection. NDS Table 10.3-1 lists all applicable<br />
adjustment factors for dowel-type connectors. Table<br />
M11.3-1 shows the applicability of adjustment factors<br />
for dowel-type fasteners in a slightly different format for<br />
the designer.<br />
Table M11.3-1 Applicability of Adjustment Factors for Dowel-Type Fasteners 1<br />
Allowable Stress Design Load and Resistance Factor Design<br />
Lateral Loads<br />
Dowel-Type Fasteners Z′ = Z C D C M C t C g C ∆ C eg C di C tn Z′ = Z C M C t C g C ∆ C eg C di C tn K F φ z λ<br />
Withdrawal Loads<br />
Nails, Spikes, Lag Screws,<br />
<strong>Wood</strong> Screws, and Drift Pins<br />
W′ = W C D C M C t C eg C tn Z′ = Z C M C t C eg C tn K F φ z λ<br />
1. See NDS Table 10.3.1 footnotes for additional guidance on application of adjustment factors for dowel-type fasteners.<br />
Example of a Dowel-Type Fastener<br />
Loaded Laterally<br />
Example of a Dowel-Type Fastener<br />
Loaded in Withdrawal<br />
For a single dowel-type fastener installed in side grain<br />
perpendicular to the length of the wood member, meeting<br />
the end and edge distance and spacing requirements of NDS<br />
11.5.1, used in a normal building environment (meeting the<br />
reference conditions of NDS 2.3 and 10.3), and not a nail<br />
or spike in diaphragm construction, the general equation<br />
for Z′ reduces to:<br />
for <strong>ASD</strong>:<br />
Z′ = Z C D<br />
for <strong>LRFD</strong>:<br />
Z′ = Z K F φ z λ<br />
M11.6 Multiple Fasteners<br />
For a single dowel-type fastener installed in side grain<br />
perpendicular to the length of the wood member, used in<br />
a normal building environment (meeting the reference<br />
conditions of NDS 2.3 and 10.3), the general equation for<br />
W′ reduces to:<br />
for <strong>ASD</strong>:<br />
W′ = W C D<br />
for <strong>LRFD</strong>:<br />
W′ = W K F φ z λ<br />
Installation Requirements<br />
To achieve stated design values, connectors must<br />
comply with installation requirements such as spacing of<br />
connectors, minimum edge and end distances, proper drilling<br />
of lead holes, and minimum fastener penetration.<br />
11<br />
M11: DOWEL-TYPE FASTENERS<br />
Local stresses in connections using multiple fasteners<br />
can be evaluated in accordance with NDS Appendix E.<br />
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M11: DOWEL-TYPE FASTENERS<br />
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M12: SPLIT<br />
RING AND<br />
SHEAR PLATE<br />
CONNECTORS<br />
M12.1 General 90<br />
M12.2 Reference Design Values 90<br />
M12.3 Placement of Split Ring and<br />
Shear Plate Connectors 90<br />
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90 M12: SPLIT RING AND SHEAR PLATE CONNECTORS<br />
M12.1 General<br />
This Chapter covers design for split rings and shear<br />
plates. These connectors rely on their geometry to provide<br />
larger metal-to-wood bearing areas per connector. Both are<br />
installed into precut grooves or daps in the members.<br />
M12.2 Reference Design Values<br />
Reference lateral design values (P, Q) are tabulated in<br />
the split ring and shear plate tables in NDS 12.2.<br />
Design Adjustment Factors<br />
10.3.1 provides all applicable adjustment factors for split<br />
ring and shear plate connectors. Table M12.2-1 shows the<br />
applicability of adjustment factors for dowel-type fasteners<br />
in a slightly different format for the designer.<br />
Split ring and shear plate connections must be designed<br />
by applying all applicable adjustment factors to the reference<br />
lateral design value for the connection. NDS Table<br />
Table M12.2-1<br />
Applicability of Adjustment Factors for Split Ring and Shear<br />
Plate Connectors 1<br />
Split Ring and<br />
Shear Plate Connectors<br />
Allowable Stress Design Load and Resistance Factor Design<br />
P′ = P C D C M C t C g C ∆ C d C st P′ = P C M C t C g C ∆ C d C st K F φ z λ<br />
Q′ = Q C D C M C t C g C ∆ C d Q′ = Q C M C t C g C ∆ C d K F φ z λ<br />
1. See NDS Table 10.3.1 footnotes for additional guidance on application of adjustment factors for split ring and shear plate connectors.<br />
For a single split ring or shear plate connection installed<br />
in side grain perpendicular to the length of the wood<br />
members, meeting the end and edge distance and spacing<br />
requirements of NDS 12.3, used in a normal building environment<br />
(meeting the reference conditions of NDS 2.3 and<br />
10.3), and meeting the penetration requirements of NDS<br />
12.2.3, the general equations for P′ and Q′ reduce to:<br />
for <strong>ASD</strong>:<br />
P′ = P C D<br />
Q′ = Q C D<br />
for <strong>LRFD</strong>:<br />
P′ = P K F φ z λ<br />
Q′ = Q K F φ z λ<br />
M12.3 Placement of Split Ring and Shear Plate<br />
Connectors<br />
Installation Requirements<br />
To achieve stated design values, connectors must<br />
comply with installation requirements such as spacing<br />
of connectors, minimum edge and end distances, proper<br />
dapping and grooving, drilling of lead holes, and minimum<br />
fastener penetration as specified in NDS 12.3.<br />
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M13: TIMBER<br />
RIVETS<br />
M13.1 General 92<br />
M13.2 Reference Design Values 92<br />
M13.3 Placement of Timber Rivets 92<br />
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92 M13: TIMBER RIVETS<br />
M13.1 General<br />
This Chapter covers design for timber rivets. Timber<br />
rivets are hardened steel nails that are driven through predrilled<br />
holes in steel side plates (typically 1/4" thickness)<br />
to form an integrated connection where the plate and rivets<br />
work together to transfer load to the wood member.<br />
M13.2 Reference Design Values<br />
Reference wood capacity design values parallel to<br />
grain, P w , are tabulated in the timber rivet Tables 13.2.1A<br />
through 13.2.1F in the NDS.<br />
Reference design values perpendicular to grain are<br />
calculated per NDS 13.2.2.<br />
for the connection. NDS Table 10.3-1 lists all applicable<br />
adjustment factors for timber rivets. Table M13.2-1 shows<br />
the applicability of adjustment factors for timber rivets in<br />
a slightly different format for the designer.<br />
Design Adjustment Factors<br />
Connections must be designed by applying all applicable<br />
adjustment factors to the reference lateral design value<br />
Table M13.2-1 Applicability of Adjustment Factors for Timber Rivets 1<br />
Timber Rivets<br />
Allowable Stress Design Load and Resistance Factor Design<br />
P′ = P C D C M C t C st P′ = P C M C t C st K F φ z λ<br />
Q′ = Q C D C M C t C ∆ Q′ = Q C M C t C ∆ K F φ z λ<br />
1. See NDS Table 10.3.1 footnotes for additional guidance on application of adjustment factors for timber rivets.<br />
For a timber rivet connection installed in side grain<br />
perpendicular to the length of the wood members, with<br />
metal side plates 1/4" or greater, used in a normal building<br />
environment (meeting the reference conditions of NDS<br />
2.3 and 10.3), and where wood capacity perpendicular to<br />
grain, Q w , does not control, the general equations for P′<br />
and Q′ reduce to:<br />
for <strong>ASD</strong>:<br />
P′ = P C D<br />
Q′ = Q C D<br />
for <strong>LRFD</strong>:<br />
P′ = P K F φ z λ<br />
Q′ = Q K F φ z λ<br />
M13.3 Placement of Timber Rivets<br />
Installation Requirements<br />
To achieve stated design values, connectors must<br />
comply with installation requirements such as spacing of<br />
connectors, minimum edge and end distances per NDS<br />
13.3; and drilling of lead holes, minimum fastener penetration,<br />
and other fabrication requirements per NDS 13.1.2.<br />
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93<br />
M14: SHEAR<br />
WALLS AND<br />
DIAPHRAGMS<br />
M14.1 General 94<br />
M14.2 Design Principles 94<br />
M14.3 Shear Walls 97<br />
M14.4 Diaphragms 98<br />
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94 M14: SHEAR WALLS AND DIAPHRAGMS<br />
M14.1 General<br />
This Chapter pertains to design of shear walls and<br />
diaphragms. These assemblies, which transfer lateral<br />
forces (wind and seismic) within the structure, are commonly<br />
designed using panel products fastened to framing<br />
members. The use of bracing systems to transfer these<br />
forces is not within the scope of this Chapter.<br />
Shear wall/diaphragm shear capacity is tabulated in<br />
the ANSI/AF&PA Special Design Provisions for Wind and<br />
Seismic (SDPWS) Supplement.<br />
M14.2 Design Principles<br />
Drag Struts/Collectors<br />
The load path for a box-type structure is from the diaphragm<br />
into the shear walls running parallel to the direction<br />
of the load (i.e., the diaphragm loads the shear walls that<br />
support it). Because the diaphragm acts like a long, deep<br />
beam, it loads each of the supporting shear walls evenly<br />
along the length of the walls. However, a wall typically<br />
contains windows and doors.<br />
The traditional model used to analyze shear walls only<br />
recognizes full height wall segments as shear wall segments.<br />
This means that at locations with windows or doors,<br />
a structural element is needed to distribute diaphragm<br />
shear over the top of the opening and into the full height<br />
segments adjacent to it. This element is called a drag strut<br />
(see Figure M14.2-1).<br />
In residential construction, the double top-plates existing<br />
in most stud walls will serve as a drag strut. It may<br />
be necessary to detail the double top plate such that no<br />
splices occur in critical zones. Or, it may be necessary to<br />
specify the use of a tension strap at butt joints to transfer<br />
these forces.<br />
The maximum force seen by drag struts is generally<br />
equal to the diaphragm design shear in the direction of<br />
the shear wall multiplied by the distance between shear<br />
wall segments.<br />
Drag struts are also used to tie together different parts<br />
of an irregularly shaped building.<br />
To simplify design, irregularly shaped buildings (such<br />
as “L” or “T” shaped) are typically divided into simple<br />
rectangles. When the structure is “reassembled” after the<br />
individual designs have been completed, drag struts are<br />
used to provide the necessary continuity between these<br />
individual segments to insure that the building will act<br />
as a whole.<br />
Figures M14.2-1, M14.2-2, and M14.2-3 and the accompanying<br />
generalized equations provide methods to<br />
calculate drag strut forces.<br />
Figure M14.2-1 Shear Wall Drag Strut<br />
V<br />
Unit shear above opening = V = v a<br />
L<br />
Unit shear below opening =<br />
V<br />
L − L<br />
Max. force in drag strut = greater of<br />
or<br />
V<br />
L L L 0 1<br />
vaLo<br />
L1<br />
=<br />
( L − L ) ( L − L )<br />
0<br />
V<br />
L L L 0 2<br />
vaLo<br />
L2<br />
=<br />
( L − L ) ( L − L )<br />
0<br />
0<br />
0<br />
L<br />
L 1<br />
L O<br />
L 2<br />
Elevation<br />
0<br />
=<br />
v b<br />
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95<br />
Figure M14.2-2 Shear Wall Special<br />
Case Drag Strut<br />
V<br />
L O<br />
Elevation<br />
Unit shear above opening = V = v a<br />
L<br />
Unit shear below opening = V L<br />
Maximum force in drag strut = L v<br />
L<br />
1<br />
=<br />
o a Force in drag strut from L 4 structure = W L 2 2<br />
( L5<br />
)<br />
2L4<br />
Figure M14.2-3 Diaphragm Drag Strut<br />
(Drag strut parallel to loads)<br />
L 1<br />
W1 L1<br />
Unit shear along L3<br />
=<br />
2L3<br />
Force in drag strut from L 3 structure = W L 1 1<br />
(<br />
L<br />
L 5)<br />
2<br />
3<br />
v b<br />
W2L2<br />
Unit shear along L4<br />
=<br />
2L4<br />
Maximum force in drag strut = L<br />
2<br />
⎛<br />
⎜<br />
W L<br />
⎝ L3<br />
5 1 1<br />
W L ⎞<br />
2 2<br />
+ ⎟<br />
L4<br />
⎠<br />
M14: SHEAR WALLS AND DIAPHRAGMS<br />
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96 M14: SHEAR WALLS AND DIAPHRAGMS<br />
Chords<br />
Diaphragms are assumed to act like long deep beams.<br />
This model assumes that shear forces are accommodated<br />
by the structural-use panel web of the “beam” and that<br />
moment forces are carried by the tension or compression<br />
forces in the flanges, or chords of the “beam.” These<br />
chord forces are often assumed to be carried by the double<br />
top-plate of the supporting perimeter walls. Given the<br />
magnitude of forces involved in most light-frame wood<br />
construction projects, the double top-plate has sufficient<br />
capacity to resist tensile and compressive forces assuming<br />
adequate detailing at splice locations. However, offset<br />
wall lines and other factors sometimes make a continuous<br />
diaphragm chord impossible.<br />
Because shear walls act as blocked, cantilevered diaphragms,<br />
they too develop chord forces and require chords.<br />
The chords in a shear wall are the double studs that are<br />
required at the end of each shear wall. Just as chords need<br />
to be continuous in a diaphragm, chords in a shear wall also<br />
need to maintain their continuity. This is accomplished by<br />
tension ties (holddowns) that are required at each end of<br />
each shear wall and between chords of stacked shear walls<br />
to provide overturning restraint. Figure M14.2-4 and the<br />
accompanying generalized equations provide a method to<br />
calculate chord forces.<br />
Figure M14.2-4 Diaphragm Chord<br />
Forces<br />
L<br />
Unit Load (wind or seismic) w<br />
Plan<br />
F(x)<br />
F(x)<br />
x<br />
L 2<br />
Diaphragm reaction = Lw 2<br />
Diaphragm unit shear = Lw L 2 2<br />
Diaphragm moment = wL2<br />
8<br />
Maximum chord force = wL 8L<br />
Chord force at point x, F(x) = wLx wx<br />
−<br />
2L<br />
2L<br />
2<br />
2<br />
2<br />
2<br />
2<br />
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97<br />
M14.3 Shear Walls<br />
Overturning<br />
Overturning moments result from shear walls being<br />
loaded by horizontal forces. Overturning moments are<br />
resisted by force couples. The tension couple is typically<br />
achieved by a holddown. Figure M14.3-1 and the accompanying<br />
equations present a method for calculating<br />
overturning forces for a non-load-bearing wall. Figure<br />
M14.3-2 and the accompanying equations present a<br />
method for calculating overturning forces for a load-bearing<br />
wall. Overturning forces for load-bearing walls can<br />
utilize dead load as overturning restraint. To effectively<br />
resist uplift forces, holddown restraints are required to<br />
show very little slip relative to the chord (end post).<br />
Figure M14.3-2 Overturning Forces<br />
(with dead load)<br />
Unit shear = V L<br />
= v<br />
Elevation<br />
Overturning force = chord force = Vh L<br />
Figure M14.3-1 Overturning Forces<br />
(no dead load)<br />
Overturning moment = Ph<br />
Dead load restraining moment* = wL2<br />
2<br />
V<br />
T<br />
L<br />
C<br />
h<br />
Net overturning moment = Ph −<br />
wL<br />
2<br />
Net overturning force – chord force = Ph −<br />
wL<br />
2<br />
L<br />
2<br />
2<br />
Ph wL<br />
= −<br />
L 2<br />
* See building code for applicable reduction to the dead load restraining moment<br />
to insure an appropriate load factor for overturning.<br />
M14: SHEAR WALLS AND DIAPHRAGMS<br />
Elevation<br />
14<br />
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98 M14: SHEAR WALLS AND DIAPHRAGMS<br />
M14.4 Diaphragms<br />
Subdiaphragms<br />
The subdiaphragm (also known as the mini-diaphragm)<br />
concept has been recognized and extensively<br />
used to provide a method of meeting wall attachment and<br />
continuous cross-tie code requirements while minimizing<br />
the number and length of ties required to achieve continuity<br />
between chords. A formal definition of a subdiaphragm<br />
can be found in SDPWS, “SUBDIAPHRAGM portion of<br />
a larger wood diaphragm designed to anchor and transfer<br />
local forces to primary diaphragm struts and the main<br />
diaphragm.”<br />
In practice, the subdiaphragm approach is used to<br />
concentrate and transfer local lateral forces to the main<br />
structural members that support vertical loads. The subdiaphragm<br />
approach is often an economical solution to code<br />
required cross-ties for the following reasons:<br />
• Main structural members are already present<br />
• Main structural members generally span the<br />
full length and width of the buildings with few<br />
connectors.<br />
• Main structural members are large enough to<br />
easily accommodate loads.<br />
• Main structural members are large enough to<br />
allow “room” for requisite connections.<br />
Each subdiaphragm must meet all applicable diaphragm<br />
requirements provided in the applicable building<br />
code. As such, each subdiaphragm must have chords,<br />
continuous tension ties, and sufficient sheathing thickness<br />
and attachment to transfer shear stresses generated within<br />
the diaphragm sheathing by the subdiaphragm. In addition,<br />
building codes may contain aspect ratios that are specific<br />
to subdiaphragms.<br />
The subdiaphragm is actually the same structure as<br />
the main roof diaphragm, thus the subdiaphragm utilizes<br />
the same roof sheathing to transfer shear stresses as the<br />
main diaphragm. As such, sheathing nailing and thickness<br />
requirements of the roof diaphragm may not be sufficient<br />
for the subdiaphragm requirements. In this case, the subdiaphragm<br />
requirements would control and dictate roof<br />
sheathing and fastening requirements in subdiaphragm<br />
locations. Fortunately, the portion of the main diaphragm<br />
that is utilized as a subdiaphragm is a choice left to the<br />
designer; thus dimensions of the subdiaphragm can be<br />
chosen to minimize potential discontinuities in sheathing<br />
thicknesses or nail schedules. Similarly, the roof diaphragm<br />
requirements may be more stringent than those<br />
for the subdiaphragm.<br />
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M15: SPECIAL<br />
LOADING<br />
CONDITIONS<br />
M15.1 Lateral Distribution of<br />
Concentrated Loads 100<br />
M15.2 Spaced Columns 100<br />
M15.3 Built-Up Columns 100<br />
M15.4 <strong>Wood</strong> Columns with Side Loads<br />
and Eccentricity 100<br />
15<br />
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100 M15: SPECIAL LOADING CONDITIONS<br />
M15.1 Lateral Distribution of Concentrated Loads<br />
M15.1.1 Lateral Distribution of a<br />
Concentrated Load for Moment<br />
The lateral distribution factors for moment in NDS<br />
Table 15.1.1 are keyed to the nominal thickness of the<br />
flooring or decking involved (2" to 6" thick). Spacing of<br />
the stringers or beams is based on recommendations of the<br />
<strong>American</strong> Association of State Highway and Transportation<br />
Officials.<br />
Lateral distribution factors determined in accordance<br />
with NDS Table 15.1.1 can be used for any type of fixed<br />
or moving concentrated load.<br />
M15.1.2 Lateral Distribution of a<br />
Concentrated Load for Shear<br />
The lateral distribution factors for shear in NDS Table<br />
15.1.2 relate the lateral distribution of concentrated load<br />
at the center of the beam or stringer span as determined<br />
under NDS 15.1.1, or by other means, to the distribution<br />
of load at the quarter points of the span. The quarter points<br />
are considered to be near the points of maximum shear in<br />
the stringers for timber bridge design.<br />
M15.2 Spaced Columns<br />
As used in the NDS, spaced columns refer to two or<br />
more individual members oriented with their longitudinal<br />
axis parallel, separated at the ends and in the middle portion<br />
of their length by blocking and joined at the ends by<br />
split ring or shear plate connectors capable of developing<br />
required shear resistance.<br />
The end fixity developed by the connectors and end<br />
blocks increases the load-carrying capacity in compression<br />
parallel to grain of the individual members only in<br />
the direction perpendicular to their wide faces.<br />
AF&PA’s <strong>Wood</strong> Structural Design Data (WSDD)<br />
provides load tables for spaced columns.<br />
M15.3 Built-Up Columns<br />
As with spaced columns, built-up columns obtain<br />
their efficiency by increasing the buckling resistance of<br />
individual laminations. The closer the laminations of a<br />
mechanically fastened built-up column deform together<br />
(the smaller the amount of slip occurring between laminations)<br />
under compressive load, the greater the relative<br />
capacity of that column compared to a simple solid column<br />
of the same slenderness ratio made with the same quality<br />
of material.<br />
M15.4 <strong>Wood</strong> Columns with Side Loads and Eccentricity<br />
The eccentric load design provisions of NDS 15.4.1<br />
are not generally applied to columns supporting beam<br />
loads where the end of the beam bears on the entire cross<br />
section of the column. It is standard practice to consider<br />
such loads to be concentrically applied to the supporting<br />
column. This practice reflects the fact that the end fixity<br />
provided by the end of the column is ignored when the<br />
usual pinned end condition is assumed in column design.<br />
In applications where the end of the beam does not bear<br />
on the full cross section of the supporting column, or in<br />
special critical loading cases, use of the eccentric column<br />
loading provisions of NDS 15.4.1 may be considered appropriate<br />
by the designer.<br />
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101<br />
M16: FIRE<br />
DESIGN<br />
M16.1 General 102<br />
Lumber 103<br />
Structural Glued Laminated<br />
Timber 119<br />
Poles and Piles 120<br />
Structural Composite Lumber 121<br />
<strong>Wood</strong> I-Joists 122<br />
Metal Plate Connected <strong>Wood</strong><br />
Trusses 131<br />
M16.2 Design Procedures for Exposed<br />
<strong>Wood</strong> Members 145<br />
M16.3 <strong>Wood</strong> Connections 159<br />
16<br />
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102 M16: FIRE DESIGN<br />
M16.1 General<br />
This Chapter outlines fire considerations including<br />
design requirements and fire-rated assemblies for various<br />
wood products. Lumber, glued laminated timber, poles<br />
and piles, wood I-joists, structural composite lumber, and<br />
metal plate connected wood trusses are discussed.<br />
Planning<br />
As a first step, the authority having jurisdiction where<br />
a proposed building is to be constructed must be consulted<br />
for the requirements of the specific design project. This<br />
normally concerns the type of construction desired as well<br />
as allowable building areas and heights for each construction<br />
type.<br />
<strong>Wood</strong> building construction is generally classified into<br />
types such as wood frame (Type V), noncombustible or<br />
fire-retardant-treated wood wall-wood joist (Type III), and<br />
heavy timber (Type IV). Type V construction is defined<br />
as having exterior walls, bearing walls, partitions, floors<br />
and roofs of wood stud and joist framing of 2" nominal<br />
dimension. These are divided into two subclasses that are<br />
either protected or unprotected construction. Protected<br />
construction calls for having load‐bearing assemblies of<br />
1‐hour fire endurance.<br />
Type III construction has exterior walls of noncombustible<br />
materials and roofs, floors, and interior walls and<br />
partitions of wood frame. As in Type V construction, these<br />
are divided into two subclasses that are either protected<br />
or unprotected.<br />
Type IV construction includes exterior walls of noncombustible<br />
materials or fire-retardant-treated wood and<br />
columns, floors, roofs, and interior partitions of wood of<br />
a minimum size, as shown in Table M16.1-1.<br />
In addition to having protected and unprotected subclasses<br />
for each building type, increases in floor area and<br />
height of the building are allowed when active fire protection,<br />
such as sprinkler protection systems, are included. For<br />
example, protected wood-frame business occupancies can<br />
be increased from three to four stories in height because<br />
of the presence of sprinklers. Also, the floor area may<br />
be further increased under some conditions. Additional<br />
information is available at www.awc.org.<br />
Table M16.1-1<br />
Material<br />
Roof decking:<br />
Lumber or structuraluse<br />
panels<br />
Floor decking:<br />
Lumber<br />
or flooring<br />
or structural-use<br />
panels<br />
Roof framing:<br />
Floor framing:<br />
Columns:<br />
Minimum Sizes to<br />
Qualify as Heavy<br />
Timber Construction<br />
Minimum size<br />
(nominal size or thickness)<br />
2 in. thickness<br />
l-l/8 in. thickness<br />
3 in. thickness<br />
1 in. thickness<br />
1/2 in. thickness<br />
4 by 6 in.<br />
6 by 10 in.<br />
8 by 8 in. (supporting floors)<br />
6 by 8 in. (supporting roofs)<br />
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103<br />
Lumber<br />
Building Code Requirements<br />
For occupancies such as stores, apartments, offices,<br />
and other commercial and industrial uses, building codes<br />
commonly require floor/ceiling and wall assemblies to be<br />
fire-resistance rated in accordance with standard fire tests.<br />
Depending on the application, wall assemblies may<br />
need to be rated either from one side or both sides. For<br />
specific exterior wall applications, the International Building<br />
Code (IBC) allows wood-frame, wood-sided walls to be<br />
tested for exposure to fire from the inside only. Rating for<br />
both interior and exterior exposure is only required when the<br />
wall has a fire separation distance of less than 5 feet. Code<br />
recognition of 1- and 2-hour wood-frame wall systems is<br />
also predicated on successful fire and hose stream testing in<br />
accordance with ASTM E119, Standard Test Methods for<br />
Fire Tests of Building Construction Materials.<br />
Fire Tested Assemblies<br />
Fire-rated wood-frame assemblies can be found in a<br />
number of sources including the IBC, Underwriters Laboratories<br />
(UL) Fire Resistance Directory, Intertek Testing<br />
Services’ Directory of Listed Products, and the Gypsum<br />
Association’s Fire Resistance Design <strong>Manual</strong>. The <strong>American</strong><br />
Forest & Paper Association (AF&PA) and its members<br />
have tested a number of wood-frame fire-rated assemblies.<br />
Descriptions of these successfully tested assemblies are<br />
provided in Tables M16.1-2 through M16.1-5.<br />
Updates<br />
Additional tests are being conducted and the Tables<br />
will be updated periodically. AF&PA’s Design for Code<br />
Acceptance (DCA) No. 3, Fire Rated <strong>Wood</strong> Floor and Wall<br />
Assemblies incorporates many of these assemblies and is<br />
available at www.awc.org.<br />
Table M16.1-2<br />
One-Hour Fire-Rated Load-Bearing <strong>Wood</strong>-Frame Wall Assemblies<br />
Assemblies Rated From Both Sides<br />
Studs Insulation Sheathing on Both Sides Fasteners Details<br />
2x4 @ 16" o.c. 3½" mineral wool batts 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 12" o.c. Figure M16.1-1<br />
2x6 @ 16" o.c. (none) 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 7" o.c. Figure M16.1-2<br />
2x6 @ 16" o.c. 5½" mineral wool batts 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 12" o.c. Figure M16.1-3<br />
2x6 @ 16" o.c. R-19 fiberglass insulation 5/8" Type X Gypsum Wallboard (V) 2¼" #6 Type S drywall screws @ 12" o.c. Figure M16.1-4<br />
Assemblies Rated From One Side (Fire on Interior Only)<br />
Studs Insulation Sheathing Fasteners Details<br />
2x4 @ 16" o.c.<br />
3½" mineral wool batts<br />
I 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 12" o.c.<br />
E 3/8" wood structural panels (V) 6d common nails @ 6" edges/12" field<br />
Figure M16.1-5<br />
I 5/8" Type X Gypsum Wallboard (V) 6d cement coated box nails @ 7" o.c.<br />
4 mil polyethylene<br />
2x4 @ 16" o.c.<br />
½" fiberboard (V) 1½" roofing nails @ 3" edges/6" field Figure M16.1-6<br />
3½" mineral wool batts E<br />
3/8" hardboard shiplapped panel siding 8d galv. nails @ 4" edges/8" field<br />
2x6 @ 16" o.c. 5½" mineral wool batts<br />
I 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 12" o.c.<br />
E 7/16" wood structural panels (V) 6d common nails @ 6" edges/12" field<br />
Figure M16.1-7<br />
2x6 @ 16" o.c. R-19 fiberglass insulation<br />
I 5/8" Type X Gypsum Wallboard (V) 2¼" #6 Type S drywall screws @ 12" o.c.<br />
E 3/8" wood structural panels (V) 6d common nails @ 6" edges/12" field<br />
Figure M16.1-8<br />
H- applied horizontally with vertical joints over studs; I- Interior sheathing; V- applied vertically with vertical joints over studs; E- Exterior sheathing<br />
M16: FIRE DESIGN<br />
Table M16.1-3 Two-Hour Fire-Rated Load-Bearing <strong>Wood</strong>-Frame Wall Assemblies<br />
Assemblies Rated From Both Sides<br />
Studs Insulation Sheathing on Both Sides Fasteners Details<br />
B 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 24" o.c.<br />
2x4 @ 24" o.c. 5½" mineral wool batts<br />
Figure M16.1-9<br />
F 5/8" Type X Gypsum Wallboard (H) 2¼" #6 Type S drywall screws @ 8" o.c.<br />
16<br />
H- applied horizontally with vertical joints over studs; B- Base layer sheathing: F- Face layer sheathing<br />
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104 M16: FIRE DESIGN<br />
Table M16.1-4<br />
One-Hour Fire-Rated <strong>Wood</strong> Floor/Ceiling Assemblies<br />
Joists Insulation Furring Ceiling Sheathing Floor Sheathing Details<br />
2x10 @ 16" o.c. none Optional F<br />
2x10 @ 16" o.c. none (none) F<br />
2x10 @ 16" o.c. none<br />
2x10 @ 24" o.c. none<br />
F- Face layer sheat<br />
Resilient<br />
channels<br />
Resilient<br />
channels<br />
F<br />
F<br />
5/8" Type X Gypsum Wallboard<br />
or ½" Type X Gypsum Wallboard<br />
½" x 24" x 48" mineral acoustical<br />
ceiling panels (see grid details)<br />
5/8" Type X Gypsum Wallboard<br />
or ½" proprietary Type Gypsum<br />
Wallboard<br />
5/8" proprietary Type Gypsum<br />
Wallboard<br />
Nom. 1" wood flooring or 19/32" T&G plywood*<br />
underlayment (single floor); building<br />
paper, and Nom. 1" T&G boards or 15/32"<br />
plywood* subfloor<br />
Nom. 19/32" T&G plywood* underlayment<br />
(single floor); building paper, and 15/32" plywood*<br />
subfloor<br />
Nom. 19/32" T&G plywood* underlayment<br />
(single floor) or 15/32" plywood* subfloor<br />
Nom. 23/32" T&G plywood* underlayment<br />
(single floor) or 15/32" plywood* subfloor<br />
Figure M16.1-10<br />
Figure M16.1-11<br />
Figure M16.1-12<br />
Figure M16.1-13<br />
Table M16.1-5<br />
Two-Hour Fire-Rated <strong>Wood</strong> Floor/Ceiling Assemblies<br />
Joists Insulation Furring Ceiling Sheathing Floor Sheathing Details<br />
2x10 @ 16" o.c.<br />
none<br />
(none) B<br />
Resilient<br />
channels<br />
F<br />
5/8" proprietary Type X<br />
Gypsum Wallboard<br />
5/8" proprietary Type X<br />
Gypsum Wallboard<br />
Nom. 1" wood flooring or 19/32" T&G plywood*<br />
underlayment (single floor); building<br />
paper, and<br />
Nom. 1" T&G boards or 15/32" plywood*<br />
subfloor<br />
Figure M16.1-14<br />
B- Base layer sheathing (direct attached); F- Face layer sheathing; *Oriented strand board (OSB) panels are permitted for certain designs. Subfloors for certain<br />
designs may be nom. 7/16" OSB.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
105<br />
Figure M16.1-1<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS4-1.1)<br />
2x4 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x4 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Sheathing: 5/8 in. Type X gypsum wallboard, 4 ft.<br />
wide, applied horizontally, unblocked. Horizontal application<br />
of wallboard represents the direction of least<br />
fire resistance as opposed to vertical application.<br />
3. Insulation: 3-1/2 in. thick mineral wool insulation.<br />
4. Fasteners: 2-1/4 in. Type S drywall screws, spaced<br />
12 in. o.c.<br />
5. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No: WP-1248 (Fire Endurance), March 29,<br />
2000<br />
WP-1246 (Hose Stream), March 9, 2000<br />
Third-Party Witness: Intertek Testing Services<br />
Report J20-06170.1<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
106 M16: FIRE DESIGN<br />
Figure M16.1-2<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-1.1)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x6 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Sheathing: 5/8 in. Type X gypsum wallboard, 4 ft.<br />
wide, applied horizontally, unblocked. Horizontal application<br />
of wallboard represents the direction of least<br />
fire resistance as opposed to vertical application.<br />
3. Fasteners: 2-1/4 in. Type S drywall screws, spaced 7<br />
in. o.c.<br />
4. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No: WP-1232 (Fire Endurance), September 16,<br />
1999<br />
WP-1234 (Hose Stream), September 27, 1999<br />
Third-Party Witness: Intertek Testing Services<br />
Report J99-22441.2<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
107<br />
Figure M16.1-3<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-1.2)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x6 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Sheathing: 5/8 in. Type X gypsum wallboard, 4 ft.<br />
wide, applied horizontally, unblocked. Horizontal application<br />
of wallboard represents the direction of least<br />
fire resistance as opposed to vertical application.<br />
3. Insulation: 5-1/2 in. thick mineral wool insulation.<br />
4. Fasteners: 2-1/4 in. Type S drywall screws, spaced<br />
12 in. o.c.<br />
5. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No:WP-1231 (Fire Endurance), September 14,<br />
1999<br />
WP-1230 (Hose Stream), August 30, 1999<br />
Third-Party Witness: Intertek Testing Services<br />
Report J99-22441.1<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
108 M16: FIRE DESIGN<br />
Figure M16.1-4<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-1.4)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x6 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate<br />
2. Sheathing: 5/8 in. Type X gypsum wallboard, 4 ft.<br />
wide, applied vertically. All panel edges backed by<br />
framing or blocking.<br />
3. Insulation: R-19 fiberglass insulation.<br />
4. Fasteners: 2-1/4 in. Type S drywall screws, spaced<br />
12 in. o.c.<br />
5. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at NGC Testing Services<br />
Test No: WP-1346 (Fire Endurance), August 22,<br />
2003<br />
WP-1351 (Hose Stream), September 17, 2003<br />
Third-Party Witness: NGC Testing Services<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
109<br />
Figure M16.1-5<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS4-1.2)<br />
2x4 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x4 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Interior Sheathing: 5/8 in. Type X gypsum wallboard,<br />
4 ft. wide, applied horizontally, unblocked. Horizontal<br />
application of wallboard represents the direction of<br />
least fire resistance as opposed to vertical application.<br />
3. Exterior Sheathing: 3/8 in. wood structural panels<br />
(oriented strand board), applied vertically, horizontal<br />
joints blocked.<br />
4. Gypsum Fasteners: 2-1/4 in. Type S drywall screws,<br />
spaced 12 in. o.c.<br />
5. Panel Fasteners: 6d common nails (bright): 12 in.<br />
o.c. in the field, 6 in. o.c. panel edges.<br />
6. Insulation: 3-1/2 in. thick mineral wool insulation.<br />
7. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No: WP-1261 (Fire Endurance & Hose Stream),<br />
November 1, 2000<br />
Third-Party Witness: Intertek Testing Services<br />
Report J20-006170.2<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
110 M16: FIRE DESIGN<br />
Figure M16.1-6<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS4-1.3)<br />
2x4 <strong>Wood</strong> Stud Wall - 78% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x4 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Interior Sheathing: 5/8 in. Type X gypsum wallboard,<br />
4 ft. wide, applied vertically, unblocked.<br />
3. Exterior Sheathing: 1/2 in. fiberboard sheathing.<br />
Alternate construction: minimum 1/2 in. lumber siding<br />
or 1/2 in. wood-based sheathing.<br />
4. Exterior Siding: 3/8 in. hardboard shiplap edge panel<br />
siding. Alternate construction lumber or wood-based,<br />
vinyl, or aluminum siding.<br />
5. Vapor Barrier: 4-mil polyethylene sheeting.<br />
6. Insulation: 3-1/2 in. thick mineral wool insulation.<br />
7. Gypsum Fasteners: 6d cement coated box nails<br />
spaced 7 in. o.c.<br />
8. Fiberboard Fasteners: 1-1/2 in. galvanized roofing<br />
nails: 6 in. o.c. in the field, 3 in. o.c. panel edges.<br />
9. Hardboard Fasteners: 8d galvanized nails: 8 in. o.c.<br />
in the field, 4 in. o.c. panel edges.<br />
10. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Gold Bond Building Products<br />
Fire Testing Laboratory<br />
Test No: WP-584 (Fire Endurance & Hose<br />
Stream), March 19, 1981<br />
Third-Party Witness: Warnock Hersey International,<br />
Inc.<br />
Report WHI-690-003<br />
This assembly was tested at 78% design load using<br />
an < e /d of 33, calculated in accordance with the 1997<br />
National Design Specification® for <strong>Wood</strong> Construction.<br />
The authority having jurisdiction should be<br />
consulted to assure acceptance of this report.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
111<br />
Figure M16.1-7<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-1.3)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x6 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Interior Sheathing: 5/8 in. Type X gypsum wallboard,<br />
4 ft. wide, applied horizontally, unblocked. Horizontal<br />
application of wallboard represents the direction of<br />
least fire resistance as opposed to vertical application.<br />
3. Exterior Sheathing: 7/16 in. wood structural panels<br />
(oriented strand board), applied vertically, horizontal<br />
joints blocked.<br />
4. Gypsum Fasteners: 2-1/4 in. Type S drywall screws,<br />
spaced 12 in. o.c.<br />
5. Panel Fasteners: 6d common nails (bright): 12 in.<br />
o.c. in the field, 6 in. o.c. panel edges.<br />
6. Insulation: 5-1/2 in. thick mineral wool insulation.<br />
7. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No: WP-1244 (Fire Endurance & Hose<br />
Stream), February 25, 2000<br />
Third-Party Witness: Intertek Testing Services<br />
Report J99-27259.2<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
112 M16: FIRE DESIGN<br />
Figure M16.1-8<br />
One-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-1.5)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 25<br />
1. Framing: Nominal 2x6 wood studs, spaced 16 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Interior Sheathing: 5/8 in. Type X gypsum wallboard,<br />
4 ft. wide, applied vertically. All panel edges backed<br />
by framing or blocking.<br />
3. Exterior Sheathing: 3/8 in. wood structural panels<br />
(oriented strand board), applied vertically, horizontal<br />
joints blocked.<br />
4. Gypsum Fasteners: 2-1/4 in. Type S drywall screws,<br />
spaced 7 in. o.c.<br />
5. Panel Fasteners: 6d common nails (bright) - 12 in.<br />
o.c. in the field, 6 in. o.c. panel edges.<br />
6. Insulation: R-19 fiberglass insulation.<br />
7. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the NGC Testing Services<br />
Test No: WP-1408 (Fire Endurance & Hose Stream)<br />
August 13, 2004<br />
Third-Party Witness: NGC Testing Services<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
113<br />
Figure M16.1-9<br />
Two-Hour Fire-Resistive <strong>Wood</strong> Wall Assembly (WS6-2.1)<br />
2x6 <strong>Wood</strong> Stud Wall - 100% Design Load - ASTM E119/NFPA 251<br />
1. Framing: Nominal 2x6 wood studs, spaced 24 in. o.c.,<br />
double top plates, single bottom plate.<br />
2. Sheathing:<br />
Base Layer: 5/8 in. Type X gypsum wallboard, 4 ft. wide,<br />
applied horizontally, unblocked.<br />
Face Layer: 5/8 in. Type X gypsum wallboard, 4 ft. wide,<br />
applied horizontally, unblocked. Horizontal application<br />
of wallboard represents the direction of least fire<br />
resistance as opposed to vertical application.<br />
3. Insulation: 5-1/2 in. thick mineral wool insulation.<br />
4. Gypsum Fasteners: Base Layer: 2-1/4 in. Type S<br />
drywall screws, spaced 24 in. o.c.<br />
5. Gypsum Fasteners: Face Layer: 2-1/4 in. Type S<br />
drywall screws, spaced 8 in. o.c.<br />
6. Joints and Fastener Heads: Wallboard joints covered<br />
with paper tape and joint compound, fastener heads<br />
covered with joint compound.<br />
Tests conducted at the Fire Test Laboratory of National<br />
Gypsum Research Center<br />
Test No: WP-1262 (Fire Endurance), November 3,<br />
2000<br />
WP-1268 (Hose Stream), December 8, 2000<br />
Third-Party Witness: Intertek Testing Services<br />
Report J20-006170.3<br />
This assembly was tested at 100% design load,<br />
calculated in accordance with the National Design<br />
Specification for <strong>Wood</strong> Construction. The authority<br />
having jurisdiction should be consulted to assure<br />
acceptance of this report.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
114 M16: FIRE DESIGN<br />
Figure M16.1-10 One-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling Assembly<br />
(2x10 <strong>Wood</strong> Joists 16" o.c. – Gypsum Directly Applied or on Optional Resilient Channels)<br />
1. Nominal 1 in. wood flooring or 19/32 in. T&G plywood<br />
underlayment (single floor). Oriented strand<br />
board (OSB) panels are permitted for certain designs.<br />
2. Building paper.<br />
3. Nominal 1 in. T&G boards or 15/32 in. plywood subfloor.<br />
Subfloors for certain designs may be nominal<br />
7/16 in. OSB.<br />
4. 1/2 in. Type X gypsum wallboard (may be attached<br />
directly to joists or on resilient channels) or 5/8 in.<br />
Type X gypsum wallboard directly applied to joists.<br />
5. 2x10 wood joists spaced 16 in. o.c.<br />
Fire Tests:<br />
1/2 in. Type X gypsum directly applied<br />
UL R1319-66, 11-9-64, Design L512;<br />
UL R3501-45, 5-27-65, Design L522;<br />
UL R2717-38, 6-10-65, Design L503;<br />
UL R3543-6, 11-10-65, Design L519;<br />
ULC Design M502<br />
1/2 in. Type X gypsum on resilient channels<br />
UL R1319-65, 11-16-64, Design L514<br />
5/8 in. Type X Gypsum directly applied<br />
UL R3501-5, 9, 7-15-52;<br />
UL R1319-2, 3, 6-5-52, Design L 501;<br />
ULC Design M500<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
115<br />
Figure M16.1-11 One-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling Assembly<br />
(2x10 <strong>Wood</strong> Joists 16" o.c. – Suspended Acoustical Ceiling Panels)<br />
1. Nominal 19/32 in. T&G plywood underlayment (single<br />
floor). Oriented strand board (OSB) panels are permitted<br />
for certain designs.<br />
2. Building paper.<br />
3. 15/32 in. plywood subfloor. Subfloors for certain designs<br />
may be nom. 7/16 in. OSB.<br />
4. 2x10 wood joists spaced 16 in. o.c.<br />
5. T-bar grid ceiling system.<br />
6. Main runners spaced 48 in. o.c.<br />
7. Cross-tees spaced 24 in. o.c.<br />
8. 1/2 in. x 24 in. x 48 in. mineral acoustical ceiling panels<br />
installed with holddown clips.<br />
Fire Tests:<br />
UL L209<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
116 M16: FIRE DESIGN<br />
Figure M16.1-12 One-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling Assembly<br />
(2x10 <strong>Wood</strong> Joists 16" o.c. – Gypsum on Resilient Channels)<br />
1. 1-1/2 in. lightweight concrete or minimum 3/4 in.<br />
proprietary gypsum concrete floor topping. Building<br />
paper may be optional and is not shown.<br />
2. 15/32 in. plywood subfloor (subfloors for certain<br />
designs may be nominal 7/16 in. OSB) or nominal<br />
19/32 in. T&G plywood underlayment (single floor).<br />
Oriented strand board (OSB) panels are permitted for<br />
certain designs.<br />
3. 2x10 wood joists spaced 16 in. o.c.<br />
4. 5/8 in. Type X Gypsum Wallboard or 1/2 in. proprietary<br />
Type X Gypsum Wallboard ceiling attached to<br />
resilient channels.<br />
Fire Tests:<br />
UL R1319-65, 11-16-64, Design L514 5/8 in. Type X<br />
gypsum<br />
UL R6352, 4-21-71, Design L502 1/2 in. proprietary<br />
Type X gypsum<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
117<br />
Figure M16.1-13 One-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling Assembly<br />
(2x10 <strong>Wood</strong> Joists 24" o.c. – Gypsum on Resilient Channels)<br />
4<br />
1, 2 not shown<br />
3<br />
6<br />
5<br />
1. 1-1/2 in. lightweight concrete or minimum 3/4 in.<br />
proprietary gypsum concrete floor topping.<br />
2. Building paper (may be optional).<br />
3. Nominal 23/32 in. T&G plywood or Oriented strand<br />
board (OSB) underlayment (single floor).<br />
4. 2x10 wood joists spaced 24 in. o.c.<br />
5. Resilient channels.<br />
6. 5/8 in. Type X Gypsum Wallboard ceiling.<br />
Fire Tests:<br />
UL R5229-2, 5-25-73, Design L513<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
118 M16: FIRE DESIGN<br />
Figure M16.1-14 Two-Hour Fire-Resistive <strong>Wood</strong> Floor/Ceiling Assembly<br />
(2x10 <strong>Wood</strong> Joists 16" o.c. – Gypsum Directly Applied with Second Layer on Resilient<br />
Channels)<br />
1. Nominal 1 in. wood flooring or 19/32 in. T&G plywood<br />
underlayment (single floor). Oriented strand<br />
board (OSB) panels are permitted for certain designs.<br />
2. Building paper.<br />
3. Nominal 1x6 T&G boards or 15/32 in. plywood subfloor.<br />
Subfloors for certain designs may be nominal<br />
7/16 in. OSB.<br />
4. 5/8 in. proprietary Type X Gypsum Wallboard ceiling<br />
attached directly to joists.<br />
5. 2x10 wood joists space 16 in. o.c.<br />
6. Resilient channels.<br />
7. 5/8 in. proprietary Type X Gypsum Wallboard ceiling<br />
attached to resilient channels.<br />
Fire Tests:<br />
UL R1319-114, 7-21-67, Design L511<br />
UL R2717-35, 10-21-64, Design L505; ULC Design<br />
M503<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
119<br />
Structural Glued Laminated Timber<br />
Fires do not normally start in structural framing, but<br />
rather in the building’s contents. These fires generally<br />
reach temperatures of between 1,290°F and 1,650°F. Glued<br />
laminated timber members perform very well under these<br />
conditions. Unprotected steel members typically suffer<br />
severe buckling and twisting during fires, often collapsing<br />
catastrophically.<br />
<strong>Wood</strong> ignites at about 480°F, but charring may begin<br />
as low as 300°F. <strong>Wood</strong> typically chars at 1/40 in. per<br />
minute. Thus, after 30 minutes of fire exposure, only the<br />
outer 3/4 in. of the structural glued laminated timber will<br />
be damaged. Char insulates a wood member and hence<br />
raises the temperature it can withstand. Most of the cross<br />
section will remain intact, and the member will continue<br />
supporting loads during a typical building fire.<br />
It is important to note that neither building materials<br />
alone, nor building features alone, nor detection and<br />
fire extinguishing equipment alone can provide adequate<br />
safety from fire in buildings. To ensure a safe structure in<br />
the event of fire, authorities base fire and building code<br />
requirements on research and testing, as well as fire histories.<br />
The model building codes classify Heavy Timber<br />
as a specific type of construction and give minimum sizes<br />
for roof and floor beams.<br />
The requirements set out for Heavy Timber construction<br />
in model building codes do not constitute 1-hour fire<br />
resistance. However, procedures are available to calculate<br />
the structural glued laminated timber size required for<br />
projects in which 1-hour fire resistance is required (see<br />
NDS 16.2 and AF&PA’s Technical Report 10 available at<br />
www.awc.org). The minimum depths for selected structural<br />
glued laminated timber sizes that can be adopted for<br />
1-hour fire ratings are given in Table M16.1-6 for structural<br />
glued laminated timber beams.<br />
To achieve a 1-hour fire rating for beams whose dimensions<br />
qualify them for this rating, the basic layup must be<br />
modified – one core lamination must be removed from the<br />
center and the tension face augmented with the addition of<br />
a tension lamination. For more information concerning the<br />
effects of fire on structural glued laminated timber, refer to<br />
APA EWS Technical Note Y245 or AITC Technical Note<br />
7. For determining fire resistance other than 1 hour, see<br />
NDS 16.2 and AF&PA’s Technical Report 10 available at<br />
www.awc.org.<br />
Table M16.1-6<br />
Minimum Depths at Which Selected Beam Sizes Can Be Adopted<br />
for One-Hour Fire Ratings 1<br />
Beam Width (in.) 3 Sides Exposed 4 Sides Exposed<br />
6-3/4 13-1/2 or 13-3/4 27 or 27-1/2<br />
8-1/2 7-1/2 or 8-1/4 15 or 15-1/8<br />
8-3/4 6-7/8 or 7-1/2 13-1/2 or 13-3/4<br />
10-1/2 6 or 6-7/8 12 or 12-3/8<br />
10-3/4 6 or 6-7/8 12 or 12-3/8<br />
1. Assuming a load factor of 1.0 (design loads are equal to the capacity of the member). The minimum<br />
depths may be reduced when the design loads are less than the member capacity.<br />
M16: FIRE DESIGN<br />
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120 M16: FIRE DESIGN<br />
Poles and Piles<br />
Very few elements of modern structures can be called<br />
“fire proof.” Even in buildings where the major structural<br />
members are noncombustible, most of the furnishings are<br />
flammable. It is for this reason that much of the attention<br />
in modern building codes addresses issues related to<br />
containing and limiting fires, rather than simply calling<br />
materials combustible and noncombustible.<br />
While this topic is fairly complex for other types of<br />
products, fire performance is relatively straightforward<br />
for poles and piles. Poles are generally used in crosssectional<br />
sizes that qualify as heavy timber construction<br />
in the model building codes. On this basis, timber poles<br />
compare favorably with other construction materials in<br />
their performance under fire conditions. Piles are generally<br />
not exposed to fire conditions unless they extend<br />
substantially above the groundline.<br />
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121<br />
Structural Composite Lumber<br />
Engineered wood products have fire resistive characteristics<br />
very similar to conventional wood frame members.<br />
Since many engineered wood products are proprietary,<br />
they are usually recognized in a code evaluation report<br />
published by an evaluation service. Each evaluation report<br />
usually contains fire resistance information.<br />
Very few elements of modern structures can be called<br />
“fire proof.” Even in buildings where the major structural<br />
members are noncombustible, most of the furnishings are<br />
flammable. It is for this reason that much of the attention in<br />
model building codes addresses issues related to containing<br />
and limiting fires, rather than simply calling materials<br />
combustible and noncombustible. The primary intent of<br />
the building codes is to ensure structural stability to allow<br />
exiting, evacuation, and fire fighting.<br />
As with the previous topic of durability, this <strong>Manual</strong><br />
cannot cover the topic of designing for optimal structural<br />
performance in fire conditions in detail. There are many<br />
excellent texts on the topic, and designers are advised to<br />
use this information early in the design process. To assist<br />
the designer in understanding several ways in which fire<br />
performance can be addressed, the following overview is<br />
provided.<br />
Fire sprinklers are probably the most effective method<br />
to enhance fire resistance of engineered wood systems (as<br />
well as other systems). They are designed to control the<br />
fire while protecting the occupants and the building until<br />
the fire department arrives. They are the ultimate way to<br />
improve fire safety.<br />
Heavy timber construction has proven to be acceptable<br />
in many areas where fire safety is of utmost concern.<br />
These applications have proven to be not only reliable, but<br />
economical in certain structures – many wider width SCL<br />
products can be used in heavy timber construction. Consult<br />
manufacturer’s literature or code evaluation reports for<br />
specific information.<br />
The fire performance of wood structures can be enhanced<br />
in the same ways as that of structures of steel,<br />
concrete, or masonry:<br />
• Fire sprinkler systems have proven to be effective<br />
in a variety of structures, both large and small<br />
• Protection of the structural members with materials<br />
such as properly attached gypsum sheathing can<br />
provide greatly improved fire performance. Fire<br />
ratings, as established from test procedures specified<br />
in ASTM E-119, of up to 2 hours can be achieved<br />
through the use of gypsum sheathing<br />
• Where surface burning characteristics are critical,<br />
fire-retardant treatments can be used to reduce the<br />
flamespread for some products<br />
To reiterate, this <strong>Manual</strong> does not purport to address<br />
this topic in an all-inclusive manner – it is merely an<br />
attempt to alert designers to the need to address fire performance<br />
issues in the design of the structure.<br />
M16: FIRE DESIGN<br />
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122 M16: FIRE DESIGN<br />
<strong>Wood</strong> I-Joists<br />
The wood I-joist industry has actively supported the<br />
following projects to establish fire performance of systems<br />
using wood I-joist products:<br />
• ASTM E-119 fire tests have been conducted by<br />
the wood I-joist industry to establish fire resistance<br />
ratings for generic I-joist systems. Detailed<br />
descriptions of these systems are shown in Figures<br />
M16.1-15 through M16.1-21 and are summarized<br />
in Table M16.1-7. In addition, sound transmission<br />
class (STC) and impact insulation class (IIC) ratings<br />
for each of these assemblies are provided. Updates<br />
to this information will be posted on the <strong>American</strong><br />
<strong>Wood</strong> <strong>Council</strong>’s website at www.awc.org.<br />
• ASTM E-119 fire tests have been conducted by<br />
wood I-joist manufacturers to establish fire resistance<br />
ratings for proprietary I-joist systems. Detailed<br />
descriptions of these systems are available from the<br />
individual I‐joist manufacturer.<br />
• National Fire Protection Research Foundation<br />
Report titled “National Engineered Lightweight<br />
Construction Fire Research Project.” This report<br />
documents an extensive literature search of the fire<br />
performance of engineered lightweight construction.<br />
• A video, I-JOISTS:FACTS ABOUT PROGRESS, has<br />
been produced by the <strong>Wood</strong> I-Joist Manufacturer’s<br />
Association (WIJMA). This video describes some<br />
basic facts about changes taking place within the<br />
construction industry and the fire service. Along<br />
with this video is a document that provides greater<br />
details on fire performance issues.<br />
• Industry research in fire endurance modeling for<br />
I-joist systems.<br />
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123<br />
Table M16.1-7<br />
Fire-Resistive <strong>Wood</strong> I-Joist Floor/Ceiling Assemblies<br />
One-Hour Assemblies<br />
Joists Insulation Furring Ceiling Sheathing Fasteners Details<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-1/2"<br />
Min. flange area: 5.25 sq. in.<br />
Min. web thickness: 3/8"<br />
Min. I-joist depth: 9-1/4"<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-1/2"<br />
Min. flange area: 5.25 sq. in.<br />
Min. web thickness: 7/16"<br />
Min. I-joist depth: 9-1/4"<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-5/16"<br />
Min. flange area: 2.25 sq. in.<br />
Min. web thickness: 3/8"<br />
Min. I-joist depth: 9-1/4"<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-1/2"<br />
Min. flange area: 3.45 sq. in.<br />
Min. web thickness: 3/8"<br />
Min. I-joist depth: 9-1/4"<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-1/2"<br />
Min. flange area: 2.25 sq. in.<br />
Min. web thickness: 3/8"<br />
Min. I-joist depth: 9-1/4"<br />
I-joists @ 24" o.c.<br />
Min. flange thickness: 1-5/16"<br />
Min. flange area: 1.95 sq. in.<br />
Min. web thickness: 3/8"<br />
Min. I-joist depth: 9-1/2"<br />
1-1/2" mineral wool<br />
batts<br />
(2.5 pcf - nominal)<br />
Resting on hat-shaped<br />
channels<br />
1-1/2" mineral wool<br />
batts<br />
(2.5 pcf - nominal)<br />
Resting on resilient<br />
channels<br />
2" mineral wool batts<br />
(3.5 pcf - nominal)<br />
Resting on 1x4 setting<br />
strips<br />
1" mineral wool batts<br />
(6 pcf - nominal) Resting<br />
on hat-shaped channels<br />
under I-joist bottom<br />
flange<br />
(none)<br />
(optional)<br />
Hat-shaped<br />
channels<br />
Resilient<br />
channels<br />
Resilient<br />
channels<br />
Hat-shaped<br />
channels<br />
supported<br />
by CSC<br />
clips<br />
(none)<br />
Resilient<br />
channels<br />
F<br />
F<br />
F<br />
F<br />
B<br />
F<br />
B<br />
F<br />
5/8" Type C Gypsum<br />
Wallboard<br />
5/8" Type C Gypsum<br />
Wallboard<br />
5/8" Type C Gypsum<br />
Wallboard<br />
1/2" Type C Gypsum<br />
Wallboard<br />
1/2" Type X Gypsum<br />
Wallboard<br />
1/2" Type X Gypsum<br />
Wallboard<br />
1/2" Type X Gypsum<br />
Wallboard<br />
1/2" Type X Gypsum<br />
Wallboard<br />
1-1/8" Type S drywall screws @ 12" o.c.<br />
(see fastening details)<br />
1" Type S drywall screws @ 8" o.c.<br />
(see fastening details)<br />
1-1/8" Type S drywall screws @ 7" o.c.<br />
(see fastening details)<br />
1" Type S drywall screws @ 12" o.c.<br />
(see fastening details)<br />
1-5/8" Type S drywall screws @ 12" o.c.<br />
2" Type S drywall screws @ 12" o.c.<br />
1-1/2" Type G drywall screws @ 8" o.c.<br />
(see fastening details)<br />
1-1/4" Type S drywall screws @ 12" o.c.<br />
1-5/8" Type S drywall screws @ 12" o.c.<br />
1-1/2" Type G drywall screws @ 8" o.c.<br />
(see fastening details)<br />
Figure<br />
M16.1-15<br />
Figure<br />
M16.1-16<br />
Figure<br />
M16.1-17<br />
Figure<br />
M16.1-18<br />
Figure<br />
M16.1-19<br />
Figure<br />
M16.1-20<br />
Two-Hour Assembly<br />
Joists Insulation Furring Ceiling Sheathing Fasteners Details<br />
5/8" Type C Gypsum<br />
I-joists @ 24" o.c.<br />
(none) B 1-5/8" Type S drywall screws @ 12" o.c.<br />
Wallboard<br />
Min. flange thickness: 1-1/2" 3-1/2" fiberglass<br />
5/8" Type C Gypsum<br />
Figure<br />
Min. flange area: 2.25 sq. in. insulation supported by<br />
M<br />
1" Type S drywall screws @ 12" o.c.<br />
Hat-shaped Wallboard<br />
M16.1-21<br />
Min. web thickness: 3/8" stay wires spaced 12" o.c.<br />
channels 5/8" Type C Gypsum 1-5/8" Type S drywall screws @ 8" o.c.<br />
Min. I-joist depth: 9-1/4"<br />
F<br />
Wallboard<br />
(see fastening details)<br />
B- Base layer sheathing (direct attached) M- Middle layer sheathing F- Face layer sheathing<br />
M16: FIRE DESIGN<br />
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<strong>American</strong> Forest & paper association
124 M16: FIRE DESIGN<br />
Figure M16.1-15 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.1)<br />
Floor a /Ceiling - 100% Design Load - 1-Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements with minimum 8d common nails and glued to joist top flanges with AFG-01 construction adhesive.<br />
3. Insulation: Minimum 1-1/2-inch-thick mineral fiber insulation batts – 2.5 pcf (nominal), supported by furring channels.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-1/2 inches Minimum I-joist flange area: 5.25 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
Flange-to-Flange Endjoint Flange-to-Web Joint Web-to-Web Endjoint<br />
Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde<br />
5. Furring Channels: Minimum 0.026-inch-thick galvanized steel hat-shaped furring channels, attached perpendicular<br />
to I-joists using 1-5/8-inch-long drywall screws. Furring channels spaced 16 inches on center and doubled at each<br />
wallboard end joint extending to the next joist.<br />
6. Gypsum Wallboard: Minimum 5/8-inch-thick Type C gypsum wallboard installed with long dimension perpendicular<br />
to furring channels and fastened to each channel with minimum 1-1/8-inch-long Type S drywall screws. Fasteners<br />
spaced 12 inches on center in the field of the wallboard, 8 inches on center at wallboard end joints, and 3/4 inch from<br />
panel edges and ends. End joints of wallboard staggered.<br />
7. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at Gold Bond Building Products Research Center: February 9, 1990<br />
Third-Party Witness: Warnock Hersey International, Inc.<br />
Report No: WHI-651-0311.1<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
- - - - - - 49 b 59 b<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
125<br />
Figure M16.1-16 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.2)<br />
Floor a /Ceiling - 100% Design Load - 1 Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements with minimum 8d common nails, and glued to joist top flanges with AFG-01 construction adhesive.<br />
3. Insulation: Minimum 1-1/2-inch-thick mineral fiber insulation batts – 2.5 pcf (nominal), supported by resilient channels.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-1/2 inches Minimum I-joist flange area: 5.25 inches 2<br />
Minimum I-joist web thickness: 7/16 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
Flange-to-Flange Endjoint Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde<br />
5. Resilient Channels: Minimum 0.019-inch-thick galvanized steel resilient channels, attached perpendicular to I-joists<br />
using 1-5/8-inch-long drywall screws. Resilient channels spaced 16 inches on center and doubled at each wallboard<br />
end joint extending to the next joist.<br />
6. Gypsum Wallboard: Minimum 5/8-inch-thick Type C gypsum wallboard installed with long dimension perpendicular<br />
to resilient channels and fastened to each channel with minimum 1-inch-long Type S drywall screws. Fasteners spaced<br />
12 inches on center in the field of the wallboard, 8 inches on center at wallboard end joints, and 3/4 inch from panel<br />
edges and ends. End joints of wallboard staggered.<br />
7. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at Gold Bond Building Research Center: June 19, 1984<br />
Third-Party Witness: Warnock Hersey International, Inc.<br />
Report No: WHI-694-0159<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
51 b 46 b 51 b 64 b 60 b 50 b 60 b 65 b<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
126 M16: FIRE DESIGN<br />
Figure M16.1-17 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.3)<br />
Floor a /Ceiling - 100% Design Load - 1-Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements.<br />
3. Insulation: Minimum 2-inch-thick mineral fiber insulation batts – 3.5 pcf (nominal), supported by setting strips edges,<br />
friction-fitted between the sides of the I-joist flanges.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-5/16 inches Minimum I-joist flange area: 2.25 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
LVL Flange Adhesive Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Emulsion Polymer Isocyanate Polyurethane Emulsion Polymer<br />
5. Setting Strips: Nominal 1x4 wood setting strips attached with 1-1/2-inch-long drywall screws at 24 inches on center<br />
along the bottom flange of I-joist creating a ledge to support insulation.<br />
6. Resilient Channels: Minimum 0.019-inch-thick galvanized steel resilient channels, attached perpendicular to I-joists<br />
using 1-7/8-inch-long drywall screws. Resilient channels spaced 16 inches on center and doubled at each wallboard<br />
end joint extending to the next joist.<br />
7. Gypsum Wallboard: Minimum 5/8-inch-thick Type C gypsum wallboard installed with long dimension perpendicular<br />
to resilient channels and fastened to each channel with minimum 1-1/8-inch-long Type S drywall screws. Fasteners<br />
spaced 7 inches on center and 3/4 inch from panel edges and ends. End joints of wallboard staggered.<br />
8. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at National Gypsum Testing Services, Inc.: September 28, 2001<br />
Third-Party Witness: Underwriter’s Laboratories, Inc.<br />
Report No: NC3369<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
51 b 46 b 52 66 60 b 48 b 60 b 60 b<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
127<br />
Figure M16.1-18 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.4)<br />
Floor a /Ceiling - 100% Design Load - 1-Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements with minimum 8d common nails.<br />
3. Insulation: Minimum 1-inch-thick mineral fiber insulation batts – 6 pcf (nominal) with width equal to the on-center<br />
spacing of the I-joists. Batts installed on top of furring channels and under bottom flange of I-joists with the sides butted<br />
against support clips. Abutted ends of batts centered over furring channels with batts tightly butted at all joints.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-1/2 inches Minimum I-joist flange area: 3.45 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
Flange-to-Flange Endjoint Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde Resorcinol-Formaldehyde<br />
5. Furring Channels: Minimum 0.019-inch-thick galvanized steel hat-shaped furring channels, attached perpendicular<br />
to I-joists spaced 24 inches on center. At channel splices, adjacent pieces overlap a minimum of 6 inches and tied<br />
with a double strand of No. 18 gage galvanized steel wire at each end of the overlap. Channels secured to I-joists<br />
with Simpson Type CSC support clips at each intersection with the I-joists. Clips nailed to the side of I-joist bottom<br />
flange with one 1-1/2-inch-long No. 11 gage nail. A row of furring channel located on each side of wallboard end<br />
joints and spaced 2.25 inches from the end joint (4.5 inches on center).<br />
6. Gypsum Wallboard: Minimum 1/2-inch-thick Type C gypsum wallboard. Wallboard installed with long dimension<br />
perpendicular to furring channels and fastened to each channel with minimum 1-inch-long Type S drywall screws.<br />
Fasteners spaced 12 inches on center in the field of the wallboard, 6 inches on center at the end joints, and 3/4 inch<br />
from panel edges and ends. End joints of wallboard continuous or staggered. For staggered wallboard end joints, furring<br />
channels extend a minimum of 6 inches beyond each end of the joint.<br />
7. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at Underwriter’s Laboratories, Inc. May 11, 1983<br />
Third-Party Witness: Underwriter’s Laboratories, Inc. Report No: UL R1037-1<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
- - 46 68 51 47 50 73<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
M16: FIRE DESIGN<br />
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<strong>American</strong> Forest & paper association
128 M16: FIRE DESIGN<br />
Figure M16.1-19 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.5)<br />
Floor a /Ceiling - 100% Design Load - 1-Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements with minimum 8d common nails.<br />
3. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-1/2 inches Minimum I-joist flange area: 2.25 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
LVL Flange Adhesive Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde<br />
4. Gypsum Wallboard: Two layers of minimum 1/2- inch Type X gypsum wallboard attached with the long dimension<br />
perpendicular to the I-joists as follows:<br />
4a. Wallboard Base Layer: Base layer of wallboard attached to bottom flange of I-joists using 1-5/8-inch Type S<br />
drywall screws at 12 inches on center. End joints of wallboard centered on bottom flange of the I-joist and staggered.<br />
4b. Wallboard Face Layer: Face layer of wallboard attached to bottom flange of I-joists through base layer using 2-<br />
inch Type S drywall screws spaced 12 inches on center on intermediate joists and 8 inches on center at end joints. Edge<br />
joints of wallboard face layer offset 24 inches from those of base layer. End joints centered on bottom flange of I-joists<br />
and offset a minimum of one joist spacing from those of base layer. Additionally, face layer of wallboard attached to base<br />
layer with 1-1/2-inch Type G drywall screws spaced 8 inches on center, placed 6 inches from face layer end joints.<br />
5. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Tests conducted at Factory Mutual Research: September 29, 1978<br />
Third-Party Witness: Factory Mutual Research:<br />
Report No: FC-268<br />
PFS Test Report #86-09-1: July 28, 1986<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
- - - - - - 49 b 55 b<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
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129<br />
Figure M16.1-20 One-Hour Fire-Resistive Ceiling Assembly (WIJ-1.6)<br />
Floor a /Ceiling - 100% Design Load - 1-Hour Rating - ASTM E 119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements with minimum 8d common nails.<br />
3. Insulation (optional, not shown): Insulation fitted between I-joists supported by the resilient channels.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-5/16 inches Minimum I-joist flange area: 1.95 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/2 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
LVL Flange Adhesive Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Emulsion Polymer Isocyanate Emulsion Polymer Isocyanate<br />
5. Resilient Channels b : Minimum 0.019-inch-thick galvanized steel resilient channel attached perpendicular to the bottom<br />
flange of the I-joists with one 1-1/4-inch drywall screw. Channels spaced a maximum of 16 inches on center [24<br />
inches on center when I-joists are spaced a maximum of 16 inches on center].<br />
6. Gypsum Wallboard: Two layers of minimum 1/2-inch Type X gypsum wallboard attached with the long dimension<br />
perpendicular to the resilient channels as follows:<br />
6a. Wallboard Base Layer: Base layer of wallboard attached to resilient channels using 1-1/4-inch Type S drywall<br />
screws at 12 inches on center.<br />
6b. Wallboard Face Layer: Face layer of wallboard attached to resilient channels through base layer using 1-5/8-inch<br />
Type S drywall screws spaced 12 inches on center. Edge joints of wallboard face layer offset 24 inches from those of<br />
base layer. Additionally, face layer of wallboard attached to base layer with 1-1/2-inch Type G drywall screws spaced<br />
8 inches on center, placed 6 inches from face layer end joints.<br />
7. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at National Research <strong>Council</strong> of Canada: Report No: A-4440.1 June 24, 1997<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
With Insulation 59 50 55 c 68 c 65 51 63 c 65 c<br />
Without Insulation - - 54 68 - - 58 c 55 c<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. Direct attachment of gypsum wallboard in lieu of attachment to resilient channels is typically deemed acceptable. When gypsum wallboard is directly attached<br />
to the I-joists, the wallboard should be installed with long dimension perpendicular to the I-joists. When insulation is used, it should be fitted between I-joists,<br />
supported above the wallboard at the spacing specified for resilient channels.<br />
c. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
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Figure M16.1-21 Two-Hour Fire-Resistive Ceiling Assembly (WIJ-2.1)<br />
Floor a /Ceiling - 100% Design Load - 2-Hour Rating - ASTM E119/NFPA 251<br />
1. Floor Topping (optional, not shown): Gypsum concrete, lightweight or normal concrete topping.<br />
2. Floor Sheathing: Minimum 23/32-inch-thick tongue-and-groove wood sheathing (Exposure 1). Installed per code<br />
requirements.<br />
3. Insulation: Minimum 3-1/2-inch-thick unfaced fiberglass insulation fitted between I-joists supported by stay wires<br />
spaced 12 inches on center.<br />
4. Structural Members: <strong>Wood</strong> I-joists spaced a maximum of 24 inches on center.<br />
Minimum I-joist flange depth: 1-1/2 inches Minimum I-joist flange area: 2.25 inches 2<br />
Minimum I-joist web thickness: 3/8 inch Minimum I-joist depth: 9-1/4 inches<br />
Types of Adhesives Used in Tested I-Joists<br />
LVL Flange Adhesive Flange-to-Web Joint Web-to-Web Endjoint<br />
Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde Phenol-Resorcinol-Formaldehyde<br />
5. Furring Channels: Minimum 0.0179-inch-thick galvanized steel hat-shaped furring channels, attached perpendicular<br />
to I-joists using 1-5/8-inch long drywall screws. Furring channels spaced 16 inches on center (furring channels used<br />
to support the second and third layers of gypsum wallboard).<br />
6. Gypsum Wallboard: Three layers of minimum 5/8-inch Type C gypsum wallboard as follows:<br />
6a. Wallboard Base Layer: Base layer of wallboard attached to bottom flange of I-joists using 1-5/8-inch Type S<br />
drywall screws at 12 inches on center with the long dimension of wallboard perpendicular to I-joist. End joints of wallboard<br />
centered on bottom flange of the I-joist and staggered from end joints in adjacent sheets.<br />
6b. Wallboard Middle Layer: Middle layer of wallboard attached to furring channels using 1-inch Type S drywall<br />
screws spaced 12 inches on center with the long dimension of wallboard perpendicular to furring channels. End joints<br />
staggered from end joints in adjacent sheets.<br />
6c. Wallboard Face Layer: Face layer of wallboard attached to furring channels through middle layer using 1-5/8-<br />
inch Type S drywall screws spaced 8 inches on center. Edge joints of wallboard face layer offset 24 inches from those<br />
of middle layer. End joints of face layer of wallboard staggered with respect to the middle layer.<br />
7. Finish System (not shown): Face layer joints covered with tape and coated with joint compound. Screw heads covered<br />
with joint compound.<br />
Fire Test conducted at Gold Bond Building Products Research Center: December 16, 1992<br />
Third-Party Witness: PFS Corporation: Report No: #92-56<br />
STC and IIC Sound Ratings for Listed Assembly<br />
Without Gypsum Concrete<br />
With Gypsum Concrete<br />
Cushioned Vinyl Carpet & Pad Cushioned Vinyl Carpet & Pad<br />
STC IIC STC IIC STC IIC STC IIC<br />
- - 49 b 54 b 52 b 46 b 52 b 60 b<br />
a. This assembly may also be used in a fire-resistive roof/ceiling application, but only when constructed exactly as described.<br />
b. STC and IIC values estimated by David L. Adams Associates, Inc.<br />
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131<br />
Metal Plate Connected <strong>Wood</strong> Trusses<br />
Generally, a fire endurance rating of 1-hour is mandated<br />
by code for many of the applications where trusses<br />
could be used. All testing on these assemblies is performed<br />
in accordance with the ASTM’s Standard Methods for<br />
Fire Tests of Building Construction and Materials (ASTM<br />
E119).<br />
The two primary source documents for fire endurance<br />
assembly results are the Fire Resistance Design <strong>Manual</strong>,<br />
published by the Gypsum Association (GA) and the Fire<br />
Resistance Directory, published by Underwriters’ Laboratories,<br />
Inc. (UL). Warnock Hersey (WH) assemblies are<br />
now listed in the ITS Directory of Listed Products. These<br />
tested assemblies are available for specification by Architects<br />
or Building Designers, and for use by all Truss<br />
Manufacturers where a rated assembly is required, and<br />
can generally be applied to both floor and roof assembly<br />
applications.<br />
According to the UL Directory’s Design Information<br />
Section: “Ratings shown on individual designs apply to<br />
equal or greater height or thickness of the assembly, and to<br />
larger structural members, when both size and weight are<br />
equal or larger than specified, and when the thickness of<br />
the flanges, web or diameter of chords is equal or greater.”<br />
Thus, larger and deeper trusses can be used under the auspices<br />
of the same design number. This approach has often<br />
been used in roof truss applications since roof trusses are<br />
usually much deeper than the tested assemblies.<br />
Thermal and/or acoustical considerations at times<br />
may require the installation of insulation in a floor-ceiling<br />
or roof-ceiling assembly that has been tested without<br />
insulation. As a general ‘rule,’ experience indicates that<br />
it is allowable to add insulation to an assembly, provided<br />
that the depth of the truss is increased by the depth of the<br />
insulation. And as a general ‘rule,’ assemblies that were<br />
tested with insulation may have the insulation removed.<br />
To make a rational assessment of any modification<br />
to a tested assembly, one must look at the properties of<br />
the insulation and the impact that its placement inside the<br />
assembly will have on the fire endurance performance<br />
of the assembly. Insulation retards the transfer of heat, is<br />
used to retain heat in warm places, and reduces the flow<br />
of heat into colder areas. As a result, its addition to a fire<br />
endurance assembly will affect the flow of heat through<br />
and within an assembly. One potential effect of insulation<br />
placed directly on the gypsum board is to retard the dissipation<br />
of heat through the assembly, concentrating heat<br />
in the protective gypsum board.<br />
In some cases specific branded products are listed in<br />
the test specifications. Modifications or substitutions to<br />
fire endurance assemblies should be reviewed with the<br />
building designer and code official, preferably with the assistance<br />
of a professional engineer. This review is required<br />
because the final performance of the assembly is a result<br />
of the composite of the materials used in the construction<br />
of the assembly.<br />
The following pages, courtesy of WTCA – Representing<br />
the Structural Building Components Industry, include<br />
brief summaries of wood truss fire endurance assemblies<br />
and sound transmission ratings. For more information, visit<br />
www.sbcindustry.com. Also, several truss plate manufacturers<br />
have developed proprietary fire resistant assemblies.<br />
These results apply only to the specific manufacturer’s<br />
truss plates and referenced fire endurance assembly system.<br />
For more detailed information on these assemblies, the<br />
individual truss plate manufacturer should be contacted.<br />
Complete specifications on the UL, GA, and WH assemblies<br />
are available at their respective websites.<br />
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Roof and Floor Assemblies<br />
The following are only summaries. Users must consult<br />
the listed testing agency’s documentation for complete<br />
information.<br />
Certifying Agencies:<br />
GA = Gypsum Association<br />
NER = National Evaluation Service Report<br />
PFS = PFS Corporation<br />
UL = Underwriters Laboratory<br />
WH = Warnock Hersey International, Ltd.<br />
Note:<br />
In some cases specific branded products are listed<br />
in the test specifications. There are situations where<br />
comparable products may be substituted.<br />
45-Minute Fire Resistive Truss Designs:<br />
PFS 88-03, FR-SYSTEM 4<br />
(floor or roof - optional insulation)<br />
Fire Rating: 45 Minutes<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, flat or floor minimum<br />
depth 15"<br />
Sloped minimum pitch 3/12, depth 19-1/2"<br />
FR-Quik Channel Sets and Bond<br />
Washers by Alpine Engineered Products<br />
One layer 5/8" Type C gypsum board<br />
Sheathing minimum 15/32"<br />
WH TSC/FCA 45-02<br />
(floor or roof - optional insulation)<br />
Fire Rating: 45 Minutes<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 10" depth<br />
Truswal metal truss plates<br />
One layer 5/8" Type X gypsum board<br />
Sheathing minimum 3/4"<br />
WH TSC/FCA 45-04<br />
(floor or roof - suspended ceiling)<br />
Fire Rating: 45 Minutes<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 10" depth<br />
Truswal metal truss plates<br />
Fire rated suspended ceiling - a minimum of<br />
7-1/2" below the joist<br />
Sheathing minimum 3/4"<br />
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133<br />
One-Hour Fire Resistive Truss Designs:<br />
GA – FC5406 & FC5408 RC2601 & RC2602<br />
(floor or roof) (see also IBC Table 720.1(3)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 9-1/4" depth<br />
Two layers 5/8" Type X gypsum board<br />
Sheathing minimum 1/2"<br />
GA – FC5512<br />
(floor or roof)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth<br />
Two layers 1/2" Type X gypsum board<br />
Sheathing minimum 19/32"<br />
GA – FC5515 or FC5516<br />
(floor or roof)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth<br />
Rigid furring channel 24" oc<br />
One layer 5/8" proprietary type X gypsum board<br />
Sheathing nominal 3/4"<br />
GA – FC5517, PFS 86-10, or TPI/WTCA FC-392<br />
(floor or roof)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 14-1/4" depth<br />
<strong>Wood</strong> blocking secured with metal clips<br />
One layer 5/8" proprietary type X gypsum board<br />
Sheathing nominal 5/8" or 23/32"<br />
NER – 392 WTCA – FR-SYSTEM 1<br />
(floor or roof - optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 23 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
16" depth<br />
FR-Quik Channel Sets and Bond<br />
Washers by Alpine Engineered Products<br />
One layer 5/8" proprietary type X gypsum board<br />
Sheathing minimum 23/32"<br />
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NER – 392 WTCA – FR-SYSTEM 3<br />
(floor or roof - optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, flat or<br />
floor minimum 15" depth<br />
Sloped minimum pitch 3/12, depth 19-1/2"<br />
FR-Quik Channel Sets and Bond<br />
Washers by Alpine Engineered Products<br />
Two layers 1/2" type X gypsum board<br />
Sheathing minimum 15/32"<br />
NER – 399<br />
(floor or roof - insulation, suspended ceiling, and<br />
light fixtures)<br />
(see WTCA Metal Plate Connected <strong>Wood</strong> Truss<br />
Handbook for details – report discontinued)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 35 Minutes<br />
Construction: <strong>Wood</strong> trusses max. 8' oc, minimum 16" depth<br />
Fire rated suspended ceiling system<br />
Purlins spaced 24" oc<br />
Sheathing minimum 23/32"<br />
PFS 89-58, FR-SYSTEM 5<br />
(floor or flat roof - insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 26 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum depth 10"<br />
2" nominal shield member<br />
FR-Quik Channel Sets and Bond<br />
Washers by Alpine Engineered Products<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
UL – L528 & L534<br />
(floor or roof)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth for<br />
L528, 18" for L534<br />
Furring channel 24" oc, alt. resilient channel<br />
16" oc<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
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135<br />
UL – L529<br />
(floor or roof - dropped ceiling, damper, duct,<br />
fixtures & metal trim)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth<br />
Ceiling system dropped 7-1/2"<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
UL – L542<br />
(floor or roof)<br />
Fire Rating: 1 Hr<br />
Finish Rating: unknown<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth<br />
Two layers 1/2" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
UL – L546<br />
(floor or roof – air duct & damper, optional<br />
insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 25 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 18" depth<br />
Resilient channel 16" oc or 12" oc<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 15/32"<br />
UL – L550, L521, L562, L563, L558, L574, and<br />
GA FC 5514<br />
(floor or roof – air duct & damper, optional<br />
insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 23 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 18" depth, 12"<br />
without damper<br />
Resilient channel 16" oc, alt. 12" oc<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
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UL – P522 & P531, P533, P538, P544, P545, and<br />
GA RC2603<br />
(pitched roof – duct or damper, optional<br />
insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 25 Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 3" or<br />
5-1/4" depth<br />
Resilient channel 16" oc<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 15/32"<br />
WH TSC/FCA 60-02<br />
(floor or roof - optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 22 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
Resilient channel 24" oc<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 3/4"<br />
WH TSC/FCA 60-04<br />
(floor or roof - suspended ceiling & fixtures,<br />
optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 27 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
Fire rated suspended ceiling - a minimum of<br />
7-1/2" below the joist<br />
Sheathing minimum 3/4"<br />
WH TSC/FCA 60-06<br />
(floor or roof - optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 24 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
TrusGard Protective Channels applied to<br />
bottom chord of each truss<br />
One layer 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 3/4"<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
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137<br />
WH TSC/FCA 60-08<br />
(floor or roof - suspended ceiling & fixtures,<br />
optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 29 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
TrusGard Protective Channels applied to<br />
bottom chord of each truss<br />
Fire rated suspended ceiling - a minimum of<br />
7-1/2" below the joist<br />
Sheathing minimum 3/4"<br />
WH TSC/FCA 60-10<br />
(floor or roof - optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 45 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
Two layers 1/2" Type X gypsum board<br />
Sheathing minimum 3/4"<br />
90-Minute Fire Resistive Truss Designs:<br />
WH TSC/FCA 90-02<br />
(floor or roof - optional insulation)<br />
Fire Rating: 90 Minutes<br />
Finish Rating: 45 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
10" depth<br />
Truswal metal truss plates<br />
Two layers 5/8" Type X gypsum board<br />
Sheathing minimum 3/4"<br />
Two-Hour Fire Resistive Truss Designs:<br />
Calculated Assembly by Kirk Grundahl, P.E.,<br />
Qualtim International, 1997<br />
(floor or roof)<br />
Fire Rating: 2 Hr<br />
Finish Rating: 90+ Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
12" depth<br />
Resilient channel 24" oc<br />
Three layers 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
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NER – 392 WTCA – FR-SYSTEM 2<br />
(floor or roof - optional insulation)<br />
Fire Rating: 2 Hr<br />
Finish Rating: 65 Minutes<br />
Construction: <strong>Wood</strong> trusses (nominal 2x3) 24" oc, minimum<br />
16" depth<br />
2" shield member attached to bottom chord<br />
FR-Quik Channel Sets and Bond<br />
Washers by Alpine Engineered Products<br />
Note: alternate installation with resilient<br />
channel added<br />
Two layers 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
PFS 89-71, FR-SYSTEM 6<br />
(floor or roof - optional insulation)<br />
Fire Rating: 2 Hr<br />
Finish Rating: 100+ Minutes<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum depth 9-1/4"<br />
Resilient channel 16" oc<br />
Three layers 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
UL L-556, GA FC 5751, and RC 2751<br />
(floor or roof – alternate truss configuration)<br />
Fire Rating: 2 Hr<br />
Finish Rating: 2 Hr<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 18" depth<br />
Resilient channel 24" oc<br />
Four layers 5/8" gypsum board<br />
Sheathing 23/32"<br />
UL L577<br />
(floor or roof - insulation)<br />
Fire Rating: 2 Hr<br />
Construction: <strong>Wood</strong> trusses 24" oc, minimum 12" depth<br />
Resilient or furring channel 16" oc<br />
Three layers 5/8" proprietary Type X gypsum<br />
board<br />
Sheathing minimum 23/32"<br />
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139<br />
Figure M16.1-22 Cross Sections of Possible One-Hour Area Separations<br />
M16: FIRE DESIGN<br />
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<strong>American</strong> Forest & paper association
140 M16: FIRE DESIGN<br />
Area Separation Assemblies<br />
It is of great concern when fire-rated assemblies are<br />
designed and specified without consideration of sound<br />
structural principles. Should a fire develop, these structural<br />
inadequacies could cause the assemblies to fail<br />
unexpectedly, increasing the risk of loss of life. There<br />
are a number of ways to provide sound structural and fire<br />
endurance details that maintain 1-hour rated area separation<br />
assemblies.<br />
Figure M16.1-22 shows several possible assemblies<br />
that can be used to make up the 1-hour rated system for<br />
separation between occupancies for a) floor trusses parallel<br />
to the wall assembly; and b) perpendicular to the wall<br />
assembly. A 2x4 firestop is used between the walls next to<br />
the wall top plates. This effectively prevents the spread of<br />
fire inside the wall cavity. A minimum 1/2-inch gypsum<br />
wallboard attached to one side of the floor truss system, and<br />
located between the floor trusses, also provides a draftstop<br />
and fire protection barrier between occupancy spaces if a<br />
fire starts in the floor truss concealed space, which is a rare<br />
occurrence. The tenant separation in the roof is maintained<br />
through the use of a 1/2-inch gypsum wallboard draftstop<br />
attached to the ends of one side of the monopitch trusses<br />
and provided for the full truss height. Figure M16.1-22<br />
effectively provides 1-hour compartmentation for all the<br />
occupied spaces using listed 1-hour rated assemblies and<br />
the appropriate draftstops for the concealed spaces as<br />
prescribed by the model building codes.<br />
If a fire-resistive assembly, rather than draftstopping,<br />
is required within concealed attic spaces, the details<br />
shown to the right (UL U338, U339, and U377) provide<br />
approved 1-hour and 2-hour rated assemblies that may be<br />
used within the roof cavity and that may be constructed<br />
with gable end frames.<br />
The critical aspects for fire endurance assemblies<br />
include:<br />
• Ensuring that the wall and ceiling assemblies of<br />
the room use 1-hour rated assemblies. These are<br />
independent assemblies. The wall assembly does<br />
not have to be continuous from the floor to the roof<br />
to meet the intent of the code or the fire endurance<br />
performance of the structure. The intent of the code<br />
is that the building be broken into compartments<br />
to contain a fire to a given area. Fire resistance<br />
assemblies are tested to provide code-complying<br />
fire endurance to meet the intent of the code. The<br />
foregoing details meet the intent of the code.<br />
• Properly fastening the gypsum wallboard to the wall<br />
studs and trusses. This is critical for achieving the<br />
desired fire performance from a UL or GA assembly.<br />
• Ensuring that the detail being used is structurally<br />
sound, particularly the bearing details. All connection<br />
details are critical to assembly performance.<br />
When a fire begins, if the structural detail is poor,<br />
the system will fail at the poor connection detail<br />
earlier than expected.<br />
• Accommodating both sound structural details with<br />
appropriate fire endurance details. Since all conceivable<br />
field conditions have not been and cannot be<br />
tested, rational engineering judgment needs to be<br />
used.<br />
The foregoing principles could also be applied to structures<br />
requiring 2-hour rated area separation assemblies. In<br />
this case, acceptable 2-hour wall assemblies would be used<br />
in conjunction with the 2-hour floor-ceiling and roof-ceiling<br />
fire endurance assemblies.<br />
Through-Penetration Fire Stops<br />
Because walls and floors are penetrated for a variety<br />
of plumbing, ventilation, electrical, and communication<br />
purposes, ASTM E814 Standard Method of Fire Tests<br />
of Through-Penetration Fire Stops uses fire-resistive<br />
assemblies (rated per ASTM E119) and penetrates them<br />
with cables, pipes, and ducts, etc., before subjecting the<br />
assembly to ASTM E119’s fire endurance tests.<br />
Despite the penetrations, firestop assemblies tested<br />
according to ASTM E814 must not significantly lose their<br />
fire containment properties in order to be considered acceptable.<br />
Properties are measured according to the passage<br />
of any heat, flame, hot gases, or combustion through the<br />
firestop to the test assembly’s unexposed surface.<br />
Upon successful completion of fire endurance tests,<br />
firestop systems are given F&T ratings. These ratings are<br />
expressed in hourly terms, in much the same fashion as<br />
fire-resistive barriers.<br />
To obtain an F-Rating, a firestop must remain in the<br />
opening during the fire and hose stream test, withstanding<br />
the fire test for a prescribed rating period without permitting<br />
the passage of flame on any element of its unexposed<br />
side. During the hose stream test, a firestop must not develop<br />
any opening that would permit a projection of water<br />
from the stream beyond the unexposed side.<br />
To obtain a T-Rating, a firestop must meet the requirements<br />
of the F-Rating. In addition, the firestop must<br />
prevent the transmission of heat during the prescribed<br />
rating period which would increase the temperature of any<br />
thermocouple on its unexposed surface, or any penetrating<br />
items, by more than 325°F.<br />
The UL Fire Resistance Directory lists literally thousands<br />
of tested systems. They have organized the systems<br />
with an alpha-alpha-numeric identification number. The<br />
first alpha is either a F, W, or C. These letters signify the<br />
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141<br />
UL – U338<br />
(wall – bearing/non-bearing, optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 20 Minutes with one layer, 59 Minutes with<br />
two layers gypsum<br />
Construction: <strong>Wood</strong> gable truss<br />
2 by 3 or 2 by 4 studs spaced 24" oc max,<br />
effectively firestopped<br />
One layer 5/8" gypsum board each side for<br />
non-bearing wall<br />
Two layers 5/8" gypsum board each side for<br />
bearing wall<br />
UL – U339<br />
(wall – bearing/non-bearing, optional insulation)<br />
Fire Rating: 1 Hr<br />
Finish Rating: 20 Minutes with one layer, 59 Minutes with<br />
two layers gypsum<br />
Construction: 2 <strong>Wood</strong> gable trusses<br />
2 by 3 or 2 by 4 studs spaced 24" oc max,<br />
effectively firestopped<br />
One layer 5/8" gypsum board each side for<br />
non-bearing wall<br />
Two layers 5/8" gypsum board each side for<br />
bearing wall<br />
Septum sheathed with plywood or<br />
mineral/fiber board (optional in bearing<br />
configuration)<br />
UL – U377<br />
(wall – bearing, required insulation)<br />
Fire Rating: 2 Hr<br />
Finish Rating: 47 Minutes with two layers gypsum<br />
Construction: Double row of nominal 2x4 studs, flat-wise,<br />
spaced 24" oc max, effectively firestopped<br />
Two layers 5/8" Type X gypsum board each<br />
side<br />
Septum filled with spray applied cellulose<br />
material<br />
Floor<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
142 M16: FIRE DESIGN<br />
type of assembly being penetrated: F signifies a floor, W<br />
signifies a wall, and C signifies a ceiling. The second alpha<br />
signifies a limiting description, for example: C signifies a<br />
framed floor, and L signifies a framed wall. The numeric<br />
portion is also significant: 0000-0999 signifies no penetrating<br />
items, 1000-1999 signifies metallic pipe, 2000-2999<br />
signifies nonmetallic pipe, 3000-3999 signifies electrical<br />
cable, 4000-4999 signifies cable trays, 5000-5999 signifies<br />
insulated pipes, 6000-6999 signifies miscellaneous<br />
electrical penetrants, 7000-7999 signifies miscellaneous<br />
mechanical penetrants, and 8000-8999 signifies a combination<br />
of penetrants.<br />
For example, a floor/ceiling penetrated by a metallic<br />
pipe would have a designation of F-C-1xxx, or with<br />
nonmetallic pipe would be designated F-C-2xxx. A few<br />
examples of floor/ceiling penetrations are included below.<br />
Examples in Figure M16.1-23 are from the UL Fire Resistance<br />
Directory, Vol. II: UL Systems F-C-2008, F-C-1006,<br />
F‐C‐3007 & 8, F-C-5002.<br />
Figure M16.1-23 Examples of Through-Penetration Firestop Systems<br />
UL F-C-2008<br />
Firestop<br />
system<br />
F-Rating - 1 Hr<br />
Pipe or Conduit<br />
T-Rating - 1 Hr<br />
F-Rating - 1 Hr<br />
T-Rating - 1 Hr<br />
UL F-C-3007<br />
General assembly<br />
General<br />
assembly<br />
Firestop<br />
system<br />
Firestop<br />
system<br />
Cables<br />
F-Rating - 1 Hr<br />
T-Rating - 1 Hr<br />
Pipe or Conduit<br />
F-Rating - 1 Hr<br />
T-Rating - 1 Hr<br />
UL F-C-3008<br />
Firestop<br />
system<br />
General<br />
assembly<br />
Cables<br />
General<br />
assembly<br />
Firestop<br />
system<br />
F-Rating - 1 Hr<br />
T-Rating - 1 Hr<br />
Firestop<br />
system<br />
UL F-C-1006<br />
Pipe or<br />
Conduit<br />
General<br />
assembly<br />
F-Rating - 1 Hr<br />
T-Rating - 1 Hr<br />
UL F-C-5002<br />
Firestop<br />
system<br />
Schedule<br />
10 Steel or<br />
copper pipe<br />
with pipe covering<br />
General<br />
assembly<br />
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<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
143<br />
Transitory Floor Vibration and Sound<br />
Transmission<br />
Sound Transmission<br />
Sound transmission ratings are closely aligned with<br />
fire endurance ratings for assemblies. This is due to the<br />
fact that flame and sound penetrations follow similar paths<br />
of least resistance.<br />
Sound striking a wall or ceiling surface is transmitted<br />
through the air in the wall or ceiling cavity. It then<br />
strikes the opposite wall surface, causing it to vibrate and<br />
transmit the sound into the adjoining room. Sound also is<br />
transmitted through any openings into the room, such as<br />
air ducts, electrical outlets, window openings, and doors.<br />
This is airborne sound transmission. The Sound Transmission<br />
Class (STC) method of rating airborne sounds<br />
evaluates the comfort ability of a particular living space.<br />
The higher the STC, the better the airborne noise control<br />
performance of the structure. An STC of 50 or above is<br />
generally considered a good airborne noise control rating.<br />
Table M16.1-6 describes the privacy afforded according<br />
to the STC rating.<br />
Impact Sound Transmission is produced when a<br />
structural element is set into vibration by direct impact<br />
– someone walking, for example. The vibrating surface<br />
generates sound waves on both sides of the element. The<br />
Impact Insulation Class (IIC) is a method of rating the<br />
impact sound transmission performance of an assembly.<br />
The higher the IIC, the better the impact noise control of<br />
the element. An IIC of 55 is generally considered a good<br />
impact noise control.<br />
Estimated <strong>Wood</strong> Floor Sound Performance 1,2,3<br />
Sound transmission and impact insulation characteristics<br />
of a floor assembly can be calculated in a manner<br />
similar to fire calculations – by adding up the value of the<br />
individual components. The contributions of various products<br />
to an STC or IIC rating are shown in Table M16.1-9.<br />
An example calculation is shown in Table M16.1-10.<br />
Tables M16.1-11 and M16.1-12 provide STC and IIC<br />
ratings for specific 1-hour fire-resistive metal plate connected<br />
wood truss assemblies. Ratings are provided for<br />
various floor coverings including combinations of carpet<br />
and pad, vinyl, lightweight concrete, and gypcrete.<br />
Table M16.1-8<br />
STC Rating<br />
Privacy Afforded<br />
25 Normal speech easily understood<br />
30 Normal speech audible, but not intelligible<br />
35 Loud speech audible and fairly understandable<br />
40 Loud speech barely audible, but not intelligible<br />
45 Loud speech barely audible<br />
50 Shouting barely audible<br />
55 Shouting inaudible<br />
Table M16.1-9<br />
Description<br />
Privacy Afforded<br />
According to STC<br />
Rating<br />
Basic wood floor - consisting of wood<br />
joist (I-joist, solid sawn, or truss) 3/4"<br />
decking and 5/8" gypsum wallboard directly<br />
attached to ceiling<br />
Contributions of<br />
Various Products to<br />
STC or IIC Rating<br />
Frequency<br />
STC<br />
High<br />
IIC<br />
Low<br />
36 33<br />
Cushioned vinyl or linoleum 0 2<br />
Non-cushioned vinyl or linoleum 0 0<br />
1/2" parquet flooring 0 1<br />
3/4" Gypcrete ® or Elastizel ® 7 to 8 1<br />
1 1/2" lightweight concrete 7 to 8 1<br />
1/2" sound deadening board (USG) 1 1 5<br />
Quiet-Cor ® underlayment by Tarkett, Inc. 1 1 8<br />
Enkasonic ® by <strong>American</strong> Enka Company 1 4 13<br />
Sempafloor ® by Laminating Services, Inc. 1 1 11<br />
R-19 batt insulation 2 0<br />
R-11 batt insulation 1 0<br />
3" mineral wool insulation 1 0<br />
Resilient channel 10 8<br />
Resilient with insulation 13 15<br />
Extra layer of 5/8" gypsum wallboard 0 to 2 2 to 4<br />
Carpet & pad 0 20 to 25<br />
1. Estimates based on proprietary literature. Verify with individual<br />
companies.<br />
M16: FIRE DESIGN<br />
16<br />
1. Acoustical <strong>Manual</strong>, National Association of Home Builders, 1978.<br />
2. Yerges, Lyle F., Sound, Noise and Vibration Control, 1969.<br />
3. Catalog of STC and IIC Ratings for Wall and Floor/Ceiling Assemblies,<br />
California Dept. of Health Services, Office of Noise Control, Berkeley, CA.<br />
<strong>American</strong> Forest & paper association
144 M16: FIRE DESIGN<br />
Table M16.1-10 Example Calculation<br />
Description STC IIC<br />
Carpet & pad 0 20<br />
3/4" Gypcrete 7 1<br />
<strong>Wood</strong> I‐joist floor 36 33<br />
Resilient channel 10 8<br />
Total 53 62<br />
Table M16.1-11 STC & IIC Ratings for UL L528/L529<br />
Floor Covering STC IIC Test Number<br />
Carpet & Pad 48 56 NRC 1039 & 1040<br />
Vinyl 45 37 NRC 1041 & 1042<br />
Lightweight, Carpet & Pad 57 72 NRC 1044 & 1045<br />
Lightweight and Vinyl 57 50* NRC 1047 & 1048<br />
Gypcrete & Cushioned Vinyl -- 53 6-442-2 Gypcrete<br />
Gypcrete, Carpet & Pad -- 74 6-442-3 Gypcrete<br />
Gypcrete 58 -- 6-442-5 Gypcrete<br />
* Does not match source document which was in error.<br />
Table M16.1-12 STC & IIC Ratings for FC-214<br />
Floor Covering STC IIC Test Number<br />
Carpet & Pad 48 54 NRC 1059 & 1060<br />
Vinyl 47 35 NRC 1063 & 1064<br />
Lightweight, Carpet & Pad 56 72 NRC 1053 & 1054<br />
Lightweight and Vinyl 56 48 NRC 1051 & 1052<br />
Gypcrete, Carpet & Pad 52 63 NRC 1076 & 1077<br />
Gypcrete 53 43 NRC 1085 & 1086<br />
Description of Materials:<br />
Gypcrete 3/4"<br />
Tables used with permission<br />
Lightweight Concrete 1"<br />
Carpet 2.63 Kg/M of Truss Plate Institute, Inc.<br />
2<br />
Pad 1.37 Kg/M 2<br />
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145<br />
M16.2 Design Procedures for Exposed <strong>Wood</strong> Members<br />
For members stressed in one principle direction, simplifications<br />
can be made which allow the tabulation of load<br />
factor tables for fire design. These load factor tables can<br />
be used to determine the structural design load ratio, R s , at<br />
which the member has sufficient capacity for a given fire<br />
endurance time. This section provides the rational used to<br />
develop the load ratio tables provided later in this section<br />
(Tables M16.2-1 through M16.2-10). For more complex<br />
calculations where stress interactions must be considered,<br />
use the provisions of AF&PA’s Technical Report 10 with<br />
the appropriate NDS provisions.<br />
Bending Members (Tables M16.2-1<br />
through M16.2-2)<br />
Load ratio tables were developed for standard reference<br />
conditions where: C D = 1.0; C M = 1.0; C t = 1.0; C L-f<br />
= 1.0<br />
The calculation of C L-s and C L-f require the designer<br />
to consider both the change in bending section relative<br />
to bending strength and the change in buckling stiffness<br />
relative to buckling strength. While these relationships can<br />
be directly calculated using NDS provisions, they can not<br />
be easily tabulated. However, for most beams exposed on<br />
three sides, the beams are braced on the protected side.<br />
For long span beams exposed on four sides, the beam<br />
failure is influenced by buckling due to lateral instability.<br />
When buckling is considered, the following equations<br />
should be used:<br />
Structural: D+L R s F b S s C L-s C D C M C t<br />
Structural (buckling): D+L R s E min I yy-s / < e C M C t<br />
Fire:<br />
D+L 2.85 F b S f C L-f<br />
Fire (buckling):<br />
D+L 2.03 E min I yy-f / < e<br />
where:<br />
where:<br />
D = Design dead load<br />
D = Design dead load<br />
L = Design live load<br />
L = Design live load<br />
R s = Design load ratio<br />
R s = Design load ratio (buckling)<br />
F b = Tabulated bending design value<br />
S s = Section modulus using full crosssection<br />
dimensions<br />
S f = Section modulus using cross-section<br />
dimensions reduced from fire exposure<br />
C L-s = Beam stability factor using full crosssection<br />
dimensions<br />
C L-f = Beam stability factor using crosssection<br />
dimensions reduced from fire<br />
exposure<br />
C D = Load duration factor<br />
C M = Wet service factor<br />
C t = Temperature factor<br />
E min = Reference modulus of elasticity for<br />
beam stability calculations<br />
I yy-s = Lateral moment of inertia using full<br />
cross-section dimensions<br />
I yy-f = Lateral moment of inertia using<br />
cross-section dimensions reduced from<br />
fire exposure<br />
R s =<br />
C M = Wet service factor<br />
C t = Temperature factor<br />
2.03 I<br />
yy- f<br />
I C C<br />
yy-s M t<br />
(M16.2-2)<br />
M16: FIRE DESIGN<br />
Solve for R s :<br />
R s =<br />
2.85 S f C L- f<br />
S C C C C<br />
s L-s D M t<br />
(M16.2-1)<br />
16<br />
<strong>American</strong> Forest & paper association
146 M16: FIRE DESIGN<br />
Compression Members (Tables<br />
M16.2-3 through M16.2-5)<br />
Structural: D+L R s F c C p-s C D C M C t<br />
I f = Moment of inertia using crosssection<br />
dimensions reduced from fire<br />
exposure<br />
C M = Wet service factor<br />
Fire:<br />
D+L 2.58 F c C p-f<br />
C t = Temperature factor<br />
where:<br />
D = Design dead load<br />
R s =<br />
2.03 I<br />
I C C<br />
s M t<br />
f<br />
(M16.2-3)<br />
L = Design live load<br />
R s = Design load ratio<br />
F c = Tabulated compression parallel-tograin<br />
design value<br />
C p-s = Column stability factor using full<br />
cross-section dimensions<br />
C p-f = Column stability factor using crosssection<br />
dimensions reduced from fire<br />
exposure<br />
C D = Load duration factor<br />
C M = Wet service factor<br />
Buckling load ratio tables were developed for standard<br />
reference conditions where: C M = 1.0; C t = 1.0<br />
NOTE: The load duration factor, C D, is not included<br />
in the load ratio tables since modulus of<br />
elasticity values, E, used in the buckling capacity<br />
calculation is not adjusted for load duration in<br />
the NDS.<br />
Tension Members (Tables M16.2-6<br />
through M16.2-8)<br />
Structural: D+L R s F t A s C D C M C t C i<br />
C t = Temperature factor<br />
Fire:<br />
D+L 2.85 F t A f<br />
The calculation of C p-s and C p-f require the designer<br />
to consider both the change in compression area relative<br />
to compression parallel-to-grain strength and the change<br />
in buckling stiffness relative to buckling strength. While<br />
these relationships can be directly calculated using NDS<br />
provisions, they can not be easily tabulated. However, for<br />
most column fire endurance designs the mode of column<br />
failure is significantly influenced by buckling. For this<br />
reason, conservative load ratio tables can be tabulated<br />
for changes in buckling capacity as a function of fire<br />
exposure.<br />
Structural (buckling): D+L R s π 2 E min I s / < e<br />
2<br />
C M C t<br />
Fire (buckling): D+L 2.03 π 2 E min I f / < e<br />
2<br />
where:<br />
D = Design dead load<br />
L = Design live load<br />
R s = Design load ratio<br />
F t = Tabulated tension parallel-to-grain<br />
design value<br />
A s = Area of cross section using full crosssection<br />
dimensions<br />
A f = Area of cross section using crosssection<br />
dimensions reduced from fire<br />
exposure<br />
C D = Load duration factor<br />
where:<br />
D = Design dead load<br />
C M = Wet service factor<br />
C t = Temperature factor<br />
L = Design live load<br />
R s = Design load ratio (buckling)<br />
E min = Reference modulus of elasticity for<br />
column stability calculations<br />
I s = Moment of inertia using full crosssection<br />
dimensions<br />
R s =<br />
2.85 A<br />
A C C C<br />
s D M t<br />
f<br />
(M16.2-4)<br />
Load ratio tables were developed for standard reference<br />
conditions where: C D = 1.0; C M = 1.0; C t = 1.0<br />
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147<br />
Table M16.2-1 Design Load Ratios for Bending Members Exposed on Three Sides<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0, C L = 1.0)<br />
(Protected Surface in Depth Direction)<br />
Table M16.2-1A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-1B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Beam Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Beam Depth Design Load Ratio, R s Beam Depth Design Load Ratio, R s<br />
5.5 0.36 0.60 0.74 0.85 0.22 0.35 0.44 0.13 0.20 6 0.42 0.65 0.82 0.93 0.25 0.41 0.52 0.18 0.26<br />
6.875 0.43 0.72 0.90 1.00 0.30 0.47 0.60 0.21 0.33 7.5 0.49 0.77 0.97 1.00 0.33 0.54 0.68 0.26 0.39<br />
8.25 0.49 0.81 1.00 1.00 0.36 0.57 0.72 0.28 0.43 9 0.54 0.85 1.00 1.00 0.38 0.64 0.79 0.33 0.49<br />
9.625 0.53 0.88 1.00 1.00 0.40 0.64 0.82 0.33 0.51 10.5 0.58 0.91 1.00 1.00 0.43 0.71 0.88 0.39 0.57<br />
11 0.56 0.93 1.00 1.00 0.44 0.70 0.89 0.37 0.58 12 0.61 0.96 1.00 1.00 0.46 0.76 0.95 0.43 0.64<br />
12.375 0.58 0.97 1.00 1.00 0.47 0.75 0.95 0.40 0.63 13.5 0.64 1.00 1.00 1.00 0.49 0.81 1.00 0.46 0.69<br />
13.75 0.60 1.00 1.00 1.00 0.49 0.78 1.00 0.43 0.67 15 0.66 1.00 1.00 1.00 0.51 0.85 1.00 0.49 0.73<br />
15.125 0.62 1.00 1.00 1.00 0.51 0.82 1.00 0.46 0.71 16.5 0.67 1.00 1.00 1.00 0.53 0.88 1.00 0.52 0.77<br />
16.5 0.63 1.00 1.00 1.00 0.53 0.84 1.00 0.48 0.74 18 0.69 1.00 1.00 1.00 0.55 0.90 1.00 0.54 0.80<br />
17.875 0.65 1.00 1.00 1.00 0.54 0.87 1.00 0.49 0.77 19.5 0.70 1.00 1.00 1.00 0.56 0.93 1.00 0.55 0.82<br />
19.25 0.66 1.00 1.00 1.00 0.56 0.89 1.00 0.51 0.79 21 0.71 1.00 1.00 1.00 0.57 0.95 1.00 0.57 0.85<br />
20.625 0.66 1.00 1.00 1.00 0.57 0.90 1.00 0.52 0.81 22.5 0.72 1.00 1.00 1.00 0.58 0.96 1.00 0.58 0.87<br />
22 0.67 1.00 1.00 1.00 0.58 0.92 1.00 0.53 0.83 24 0.73 1.00 1.00 1.00 0.59 0.98 1.00 0.60 0.88<br />
23.375 0.68 1.00 1.00 1.00 0.59 0.93 1.00 0.55 0.85 25.5 0.73 1.00 1.00 1.00 0.60 0.99 1.00 0.61 0.90<br />
24.75 0.69 1.00 1.00 1.00 0.60 0.95 1.00 0.55 0.86 27 0.74 1.00 1.00 1.00 0.61 1.00 1.00 0.62 0.91<br />
26.125 0.69 1.00 1.00 1.00 0.60 0.96 1.00 0.56 0.88 28.5 0.74 1.00 1.00 1.00 0.61 1.00 1.00 0.62 0.93<br />
27.5 0.70 1.00 1.00 1.00 0.61 0.97 1.00 0.57 0.89 30 0.75 1.00 1.00 1.00 0.62 1.00 1.00 0.63 0.94<br />
28.875 0.70 1.00 1.00 1.00 0.61 0.98 1.00 0.58 0.90 31.5 0.75 1.00 1.00 1.00 0.62 1.00 1.00 0.64 0.95<br />
30.25 0.71 1.00 1.00 1.00 0.62 0.99 1.00 0.58 0.91 33 0.76 1.00 1.00 1.00 0.63 1.00 1.00 0.65 0.96<br />
31.625 0.71 1.00 1.00 1.00 0.62 0.99 1.00 0.59 0.92 34.5 0.76 1.00 1.00 1.00 0.63 1.00 1.00 0.65 0.97<br />
33 0.71 1.00 1.00 1.00 0.63 1.00 1.00 0.60 0.93 36 0.77 1.00 1.00 1.00 0.64 1.00 1.00 0.66 0.98<br />
34.375 0.72 1.00 1.00 1.00 0.63 1.00 1.00 0.60 0.93 37.5 1.00 1.00 1.00 0.64 1.00 1.00 0.66 0.98<br />
35.75 0.72 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.94 39 1.00 1.00 1.00 0.64 1.00 1.00 0.67 0.99<br />
37.125 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.95 40.5 1.00 1.00 1.00 0.65 1.00 1.00 0.67 1.00<br />
38.5 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.95 42 1.00 1.00 1.00 0.65 1.00 1.00 0.68 1.00<br />
39.875 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.96 43.5 1.00 1.00 1.00 0.65 1.00 1.00 0.68 1.00<br />
41.25 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.97 45 1.00 1.00 1.00 0.66 1.00 1.00 0.68 1.00<br />
42.625 1.00 1.00 1.00 0.65 1.00 1.00 0.63 0.97 46.5 1.00 1.00 1.00 0.66 1.00 1.00 0.69 1.00<br />
44 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 48 1.00 1.00 1.00 0.66 1.00 1.00 0.69 1.00<br />
45.375 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 49.5 1.00 1.00 1.00 1.00 0.69 1.00<br />
46.75 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.99 51 1.00 1.00 1.00 1.00 0.70 1.00<br />
48.125 1.00 1.00 1.00 0.66 1.00 1.00 0.64 0.99 52.5 1.00 1.00 1.00 1.00 0.70 1.00<br />
49.5 1.00 1.00 1.00 1.00 0.64 0.99 54 1.00 1.00 1.00 1.00 0.70 1.00<br />
50.875 1.00 1.00 1.00 1.00 0.64 1.00 55.5 1.00 1.00 1.00 1.00 0.70 1.00<br />
52.25 1.00 1.00 1.00 1.00 0.64 1.00 57 1.00 1.00 1.00 1.00 0.70 1.00<br />
53.625 1.00 1.00 1.00 1.00 0.65 1.00 58.5 1.00 1.00 1.00 1.00 0.71 1.00<br />
55 1.00 1.00 1.00 1.00 0.65 1.00 60 1.00 1.00 1.00 1.00 0.71 1.00<br />
56.375 1.00 1.00 1.00 1.00 0.65 1.00 61.5 1.00 1.00 1.00 1.00 0.71 1.00<br />
57.75 1.00 1.00 1.00 1.00 0.65 1.00 63 1.00 1.00 1.00 1.00 0.71 1.00<br />
59.125 1.00 1.00 1.00 1.00 0.65 1.00 64.5 1.00 1.00 1.00<br />
60.5 1.00 1.00 1.00 1.00 0.66 1.00 66 1.00 1.00 1.00<br />
61.875 1.00 1.00 1.00 1.00 0.66 1.00 67.5 1.00 1.00 1.00<br />
63.25 1.00 1.00 1.00 1.00 0.66 1.00 69 1.00 1.00 1.00<br />
64.625 1.00 1.00 1.00 70.5 1.00 1.00 1.00<br />
66 1.00 1.00 1.00 72 1.00 1.00 1.00<br />
67.375 1.00 1.00 1.00 73.5 1.00 1.00 1.00<br />
68.75 1.00 1.00 1.00 75 1.00 1.00 1.00<br />
70.125 1.00 1.00 1.00 76.5 1.00 1.00 1.00<br />
71.5 1.00 1.00 1.00 78 1.00 1.00 1.00<br />
72.875 1.00 1.00 1.00 79.5 1.00 1.00 1.00<br />
74.25 1.00 1.00 1.00 81 1.00 1.00 1.00<br />
75.625 1.00 1.00 1.00<br />
77 1.00 1.00 1.00 Note: Tabulated values assume bending in the depth direction.<br />
Table M16.2-1C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Beam Depth<br />
Design Load Ratio, R s<br />
5.5 0.45 0.67 0.80 0.89 0.28 0.40 0.48 0.17 0.23<br />
7.5 0.57 0.86 1.00 1.00 0.42 0.60 0.71 0.32 0.43<br />
9.5 0.65 0.97 1.00 1.00 0.51 0.73 0.87 0.42 0.57<br />
11.5 0.70 1.00 1.00 1.00 0.58 0.83 0.99 0.50 0.67<br />
13.5 0.74 1.00 1.00 1.00 0.63 0.89 1.00 0.56 0.75<br />
15.5 0.77 1.00 1.00 1.00 0.67 0.95 1.00 0.60 0.81<br />
17.5 0.79 1.00 1.00 1.00 0.70 0.99 1.00 0.64 0.86<br />
19.5 0.81 1.00 1.00 1.00 0.72 1.00 1.00 0.67 0.90<br />
21.5 0.83 1.00 1.00 1.00 0.74 1.00 1.00 0.69 0.93<br />
23.5 0.84 1.00 1.00 1.00 0.76 1.00 1.00 0.71 0.96<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
148 M16: FIRE DESIGN<br />
Table M16.2-2 Design Load Ratios for Bending Members Exposed on Four Sides<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0, C L =1.0)<br />
Table M16.2-2A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-2B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Beam Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Beam Depth Design Load Ratio, R s Beam Depth Design Load Ratio, R s<br />
5.5 0.10 0.16 0.20 0.22 0.01 0.01 0.01 0.02 0.03 6 0.14 0.21 0.27 0.30 0.02 0.03 0.04 0.00 0.00<br />
6.875 0.18 0.30 0.37 0.42 0.05 0.09 0.11 0.00 0.01 7.5 0.23 0.36 0.45 0.51 0.08 0.13 0.17 0.02 0.03<br />
8.25 0.25 0.42 0.52 0.59 0.11 0.18 0.23 0.04 0.06 9 0.31 0.48 0.60 0.68 0.15 0.24 0.30 0.07 0.10<br />
9.625 0.31 0.52 0.64 0.73 0.17 0.27 0.34 0.09 0.13 10.5 0.37 0.57 0.72 0.82 0.20 0.33 0.42 0.12 0.19<br />
11 0.36 0.60 0.74 0.85 0.22 0.35 0.44 0.13 0.20 12 0.42 0.65 0.82 0.93 0.25 0.41 0.52 0.18 0.26<br />
12.375 0.40 0.67 0.83 0.94 0.26 0.42 0.53 0.17 0.27 13.5 0.46 0.72 0.90 1.00 0.29 0.48 0.60 0.22 0.33<br />
13.75 0.43 0.72 0.90 1.00 0.30 0.47 0.60 0.21 0.33 15 0.49 0.77 0.97 1.00 0.33 0.54 0.68 0.26 0.39<br />
15.125 0.46 0.77 0.95 1.00 0.33 0.52 0.67 0.25 0.38 16.5 0.52 0.81 1.00 1.00 0.36 0.59 0.74 0.30 0.45<br />
16.5 0.49 0.81 1.00 1.00 0.36 0.57 0.72 0.28 0.43 18 0.54 0.85 1.00 1.00 0.38 0.64 0.79 0.33 0.49<br />
17.875 0.51 0.85 1.00 1.00 0.38 0.61 0.77 0.30 0.47 19.5 0.56 0.88 1.00 1.00 0.41 0.67 0.84 0.36 0.54<br />
19.25 0.53 0.88 1.00 1.00 0.40 0.64 0.82 0.33 0.51 21 0.58 0.91 1.00 1.00 0.43 0.71 0.88 0.39 0.57<br />
20.625 0.54 0.91 1.00 1.00 0.42 0.67 0.86 0.35 0.54 22.5 0.60 0.94 1.00 1.00 0.45 0.74 0.92 0.41 0.61<br />
22 0.56 0.93 1.00 1.00 0.44 0.70 0.89 0.37 0.58 24 0.61 0.96 1.00 1.00 0.46 0.76 0.95 0.43 0.64<br />
23.375 0.57 0.95 1.00 1.00 0.45 0.72 0.92 0.39 0.60 25.5 0.63 0.98 1.00 1.00 0.48 0.79 0.98 0.45 0.66<br />
24.75 0.58 0.97 1.00 1.00 0.47 0.75 0.95 0.40 0.63 27 0.64 1.00 1.00 1.00 0.49 0.81 1.00 0.46 0.69<br />
26.125 0.59 0.99 1.00 1.00 0.48 0.77 0.97 0.42 0.65 28.5 0.65 1.00 1.00 1.00 0.50 0.83 1.00 0.48 0.71<br />
27.5 0.60 1.00 1.00 1.00 0.49 0.78 1.00 0.43 0.67 30 0.66 1.00 1.00 1.00 0.51 0.85 1.00 0.49 0.73<br />
28.875 0.61 1.00 1.00 1.00 0.50 0.80 1.00 0.44 0.69 31.5 0.67 1.00 1.00 1.00 0.52 0.86 1.00 0.50 0.75<br />
30.25 0.62 1.00 1.00 1.00 0.51 0.82 1.00 0.46 0.71 33 0.67 1.00 1.00 1.00 0.53 0.88 1.00 0.52 0.77<br />
31.625 0.63 1.00 1.00 1.00 0.52 0.83 1.00 0.47 0.73 34.5 0.68 1.00 1.00 1.00 0.54 0.89 1.00 0.53 0.78<br />
33 0.63 1.00 1.00 1.00 0.53 0.84 1.00 0.48 0.74 36 0.69 1.00 1.00 1.00 0.55 0.90 1.00 0.54 0.80<br />
34.375 0.64 1.00 1.00 1.00 0.54 0.86 1.00 0.49 0.75 37.5 1.00 1.00 1.00 0.55 0.92 1.00 0.55 0.81<br />
35.75 0.65 1.00 1.00 1.00 0.54 0.87 1.00 0.49 0.77 39 1.00 1.00 1.00 0.56 0.93 1.00 0.55 0.82<br />
37.125 1.00 1.00 1.00 0.55 0.88 1.00 0.50 0.78 40.5 1.00 1.00 1.00 0.57 0.94 1.00 0.56 0.84<br />
38.5 1.00 1.00 1.00 0.56 0.89 1.00 0.51 0.79 42 1.00 1.00 1.00 0.57 0.95 1.00 0.57 0.85<br />
39.875 1.00 1.00 1.00 0.56 0.90 1.00 0.52 0.80 43.5 1.00 1.00 1.00 0.58 0.96 1.00 0.58 0.86<br />
41.25 1.00 1.00 1.00 0.57 0.90 1.00 0.52 0.81 45 1.00 1.00 1.00 0.58 0.96 1.00 0.58 0.87<br />
42.625 1.00 1.00 1.00 0.57 0.91 1.00 0.53 0.82 46.5 1.00 1.00 1.00 0.59 0.97 1.00 0.59 0.88<br />
44 1.00 1.00 1.00 0.58 0.92 1.00 0.53 0.83 48 1.00 1.00 1.00 0.59 0.98 1.00 0.60 0.88<br />
45.375 1.00 1.00 1.00 0.58 0.93 1.00 0.54 0.84 49.5 1.00 1.00 0.99 1.00 0.60 0.89<br />
46.75 1.00 1.00 1.00 0.59 0.93 1.00 0.55 0.85 51 1.00 1.00 0.99 1.00 0.61 0.90<br />
48.125 1.00 1.00 1.00 0.59 0.94 1.00 0.55 0.85 52.5 1.00 1.00 1.00 1.00 0.61 0.91<br />
49.5 1.00 1.00 0.95 1.00 0.55 0.86 54 1.00 1.00 1.00 1.00 0.62 0.91<br />
50.875 1.00 1.00 0.95 1.00 0.56 0.87 55.5 1.00 1.00 1.00 1.00 0.62 0.92<br />
52.25 1.00 1.00 0.96 1.00 0.56 0.88 57 1.00 1.00 1.00 1.00 0.62 0.93<br />
53.625 1.00 1.00 0.96 1.00 0.57 0.88 58.5 1.00 1.00 1.00 1.00 0.63 0.93<br />
55 1.00 1.00 0.97 1.00 0.57 0.89 60 1.00 1.00 1.00 1.00 0.63 0.94<br />
56.375 1.00 1.00 0.97 1.00 0.57 0.89 61.5 1.00 1.00 1.00 1.00 0.64 0.94<br />
57.75 1.00 1.00 0.98 1.00 0.58 0.90 63 1.00 1.00 1.00 1.00 0.64 0.95<br />
59.125 1.00 1.00 0.98 1.00 0.58 0.90 64.5 1.00 1.00 0.95<br />
60.5 1.00 1.00 0.99 1.00 0.58 0.91 66 1.00 1.00 0.96<br />
61.875 1.00 1.00 0.99 1.00 0.59 0.91 67.5 1.00 1.00 0.96<br />
63.25 1.00 1.00 0.99 1.00 0.59 0.92 69 1.00 1.00 0.97<br />
64.625 1.00 1.00 0.92 70.5 1.00 1.00 0.97<br />
66 1.00 1.00 0.93 72 1.00 1.00 0.98<br />
67.375 1.00 1.00 0.93 73.5 1.00 1.00 0.98<br />
68.75 1.00 1.00 0.93 75 1.00 1.00 0.98<br />
70.125 1.00 1.00 0.94 76.5 1.00 1.00 0.99<br />
71.5 1.00 1.00 0.94 78 1.00 1.00 0.99<br />
72.875 1.00 1.00 0.95 79.5 1.00 1.00 0.99<br />
74.25 1.00 1.00 0.95 81 1.00 1.00 1.00<br />
75.625 1.00 1.00 0.95<br />
77 1.00 1.00 0.95<br />
Note: Tabulated values assume bending in the depth direction.<br />
Table M16.2-2C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Beam Depth<br />
Design Load Ratio, R s<br />
5.5 0.12 0.18 0.21 0.23 0.01 0.01 0.01 0.02 0.03<br />
7.5 0.27 0.40 0.48 0.53 0.10 0.15 0.18 0.02 0.03<br />
9.5 0.38 0.57 0.68 0.76 0.21 0.30 0.36 0.11 0.14<br />
11.5 0.46 0.70 0.84 0.92 0.30 0.43 0.51 0.19 0.26<br />
13.5 0.53 0.80 0.95 1.00 0.38 0.53 0.64 0.27 0.36<br />
15.5 0.58 0.87 1.00 1.00 0.43 0.62 0.74 0.33 0.45<br />
17.5 0.62 0.93 1.00 1.00 0.48 0.69 0.82 0.39 0.52<br />
19.5 0.65 0.99 1.00 1.00 0.52 0.74 0.89 0.43 0.59<br />
21.5 0.68 1.00 1.00 1.00 0.56 0.79 0.95 0.47 0.64<br />
23.5 0.71 1.00 1.00 1.00 0.59 0.84 1.00 0.51 0.69<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
149<br />
Table M16.2-3 Design Load Ratios for Compression Members Exposed on Three<br />
Sides<br />
(Structural Calculations at Standard Reference Conditions: C M = 1.0, C t = 1.0, C i = 1.0)<br />
(Protected Surface in Depth Direction)<br />
Table M16.2-3A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-3B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Col. Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Col. Depth Design Load Ratio, R s Col. Depth Design Load Ratio, R s<br />
5.5 0.03 6 0.04<br />
6.875 0.03 0.15 0.02 7.5 0.04 0.16 0.02<br />
8.25 0.03 0.16 0.30 0.02 0.10 0.02 9 0.04 0.17 0.33 0.03 0.10 0.03<br />
9.625 0.04 0.17 0.32 0.47 0.03 0.10 0.22 0.02 0.09 10.5 0.04 0.17 0.34 0.49 0.03 0.11 0.22 0.03 0.10<br />
11 0.04 0.17 0.33 0.48 0.03 0.11 0.22 0.02 0.09 12 0.05 0.18 0.35 0.51 0.03 0.11 0.23 0.03 0.10<br />
12.375 0.04 0.18 0.33 0.49 0.03 0.11 0.23 0.03 0.10 13.5 0.05 0.18 0.36 0.52 0.03 0.11 0.24 0.03 0.11<br />
13.75 0.04 0.18 0.34 0.50 0.03 0.12 0.24 0.03 0.10 15 0.05 0.18 0.36 0.53 0.03 0.12 0.24 0.03 0.11<br />
15.125 0.04 0.18 0.34 0.51 0.03 0.12 0.24 0.03 0.10 16.5 0.05 0.18 0.37 0.53 0.03 0.12 0.25 0.03 0.11<br />
16.5 0.04 0.18 0.35 0.51 0.03 0.12 0.25 0.03 0.10 18 0.05 0.19 0.37 0.54 0.03 0.12 0.25 0.04 0.12<br />
17.875 0.04 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 19.5 0.05 0.19 0.38 0.54 0.03 0.12 0.25 0.04 0.12<br />
19.25 0.04 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 21 0.05 0.19 0.38 0.55 0.03 0.12 0.26 0.04 0.12<br />
20.625 0.04 0.19 0.35 0.53 0.03 0.12 0.26 0.03 0.11 22.5 0.05 0.19 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
22 0.04 0.19 0.36 0.53 0.03 0.12 0.26 0.03 0.11 24 0.05 0.19 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
23.375 0.04 0.19 0.36 0.53 0.03 0.13 0.26 0.03 0.11 25.5 0.05 0.19 0.38 0.56 0.03 0.13 0.26 0.04 0.12<br />
24.75 0.04 0.19 0.36 0.53 0.03 0.13 0.26 0.03 0.11 27 0.05 0.19 0.39 0.56 0.03 0.13 0.26 0.04 0.13<br />
26.125 0.04 0.19 0.36 0.54 0.03 0.13 0.26 0.03 0.11 28.5 0.05 0.19 0.39 0.56 0.03 0.13 0.27 0.04 0.13<br />
27.5 0.04 0.19 0.36 0.54 0.03 0.13 0.26 0.03 0.11 30 0.05 0.19 0.39 0.56 0.03 0.13 0.27 0.04 0.13<br />
28.875 0.04 0.19 0.36 0.54 0.03 0.13 0.27 0.03 0.11 31.5 0.05 0.19 0.39 0.56 0.03 0.13 0.27 0.04 0.13<br />
30.25 0.04 0.19 0.37 0.54 0.03 0.13 0.27 0.03 0.11 33 0.05 0.20 0.39 0.56 0.03 0.13 0.27 0.04 0.13<br />
31.625 0.04 0.19 0.37 0.54 0.03 0.13 0.27 0.03 0.11 34.5 0.05 0.20 0.39 0.57 0.03 0.13 0.27 0.04 0.13<br />
33 0.04 0.20 0.37 0.54 0.03 0.13 0.27 0.03 0.12 36 0.05 0.20 0.39 0.57 0.03 0.13 0.27 0.04 0.13<br />
34.375 0.04 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 37.5 0.20 0.39 0.57 0.03 0.13 0.27 0.04 0.13<br />
35.75 0.04 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 39 0.20 0.39 0.57 0.03 0.13 0.27 0.04 0.13<br />
37.125 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 40.5 0.20 0.40 0.57 0.03 0.13 0.27 0.04 0.13<br />
38.5 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 42 0.20 0.40 0.57 0.03 0.13 0.27 0.04 0.13<br />
39.875 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 43.5 0.20 0.40 0.57 0.03 0.13 0.27 0.04 0.13<br />
41.25 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 45 0.20 0.40 0.57 0.03 0.13 0.27 0.04 0.13<br />
42.625 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 46.5 0.20 0.40 0.57 0.03 0.13 0.28 0.04 0.13<br />
44 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 48 0.20 0.40 0.57 0.03 0.13 0.28 0.04 0.13<br />
45.375 0.20 0.37 0.55 0.03 0.13 0.27 0.03 0.12 49.5 0.40 0.58 0.03 0.13 0.28 0.04 0.13<br />
46.75 0.20 0.37 0.55 0.03 0.13 0.28 0.03 0.12 51 0.40 0.58 0.03 0.13 0.28 0.04 0.13<br />
48.125 0.20 0.37 0.55 0.03 0.13 0.28 0.03 0.12 52.5 0.40 0.58 0.03 0.13 0.28 0.04 0.13<br />
49.5 0.37 0.56 0.13 0.28 0.03 0.12 54 0.40 0.58 0.13 0.28 0.04 0.13<br />
50.875 0.38 0.56 0.13 0.28 0.03 0.12 55.5 0.40 0.58 0.13 0.28 0.04 0.13<br />
52.25 0.38 0.56 0.13 0.28 0.03 0.12 57 0.40 0.58 0.13 0.28 0.04 0.13<br />
53.625 0.38 0.56 0.13 0.28 0.03 0.12 58.5 0.40 0.58 0.13 0.28 0.04 0.13<br />
55 0.38 0.56 0.13 0.28 0.03 0.12 60 0.40 0.58 0.14 0.28 0.04 0.13<br />
56.375 0.38 0.56 0.13 0.28 0.03 0.12 61.5 0.40 0.58 0.14 0.28 0.04 0.13<br />
57.75 0.38 0.56 0.13 0.28 0.03 0.12 63 0.40 0.58 0.14 0.28 0.04 0.13<br />
59.125 0.38 0.56 0.14 0.28 0.03 0.12 64.5 0.58 0.14 0.28 0.13<br />
60.5 0.38 0.56 0.14 0.28 0.03 0.12 66 0.58 0.14 0.28 0.13<br />
61.875 0.38 0.56 0.14 0.28 0.03 0.12 67.5 0.58 0.14 0.28 0.13<br />
63.25 0.38 0.56 0.14 0.28 0.03 0.12 69 0.58 0.14 0.28 0.14<br />
64.625 0.56 0.28 0.12 70.5 0.58 0.28 0.14<br />
66 0.56 0.28 0.12 72 0.58 0.28 0.14<br />
67.375 0.56 0.28 0.12 73.5 0.58 0.28 0.14<br />
68.75 0.56 0.28 0.12 75 0.58 0.28 0.14<br />
70.125 0.56 0.28 0.12 76.5 0.58 0.28 0.14<br />
71.5 0.56 0.28 0.12 78 0.58 0.28 0.14<br />
72.875 0.56 0.28 0.12 79.5 0.58 0.28 0.14<br />
74.25 0.56 0.28 0.12 81 0.58 0.28 0.14<br />
75.625 0.56 0.28 0.12<br />
77 0.56 0.28 0.12<br />
Table M16.2-3C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Col. Depth<br />
Design Load Ratio, R s<br />
5.5 0.06<br />
7.5 0.06 0.22 0.05<br />
9.5 0.07 0.23 0.39 0.05 0.16 0.05<br />
11.5 0.07 0.24 0.41 0.56 0.06 0.17 0.29 0.05 0.13<br />
13.5 0.07 0.25 0.42 0.57 0.06 0.18 0.30 0.06 0.14<br />
15.5 0.07 0.25 0.43 0.58 0.06 0.18 0.31 0.06 0.15<br />
17.5 0.08 0.26 0.44 0.59 0.06 0.18 0.31 0.06 0.15<br />
19.5 0.08 0.26 0.44 0.60 0.07 0.19 0.32 0.06 0.16<br />
21.5 0.08 0.26 0.45 0.60 0.07 0.19 0.32 0.06 0.16<br />
23.5 0.08 0.26 0.45 0.61 0.07 0.19 0.33 0.07 0.16<br />
Notes:<br />
1. Tabulated values assume bending in the width direction.<br />
2. Tabulated values conservatively assume column buckling failure. For relatively<br />
short, highly loaded columns, a more rigorous analysis using the NDS<br />
provisions will increase the design load ratio, R s .<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
150 M16: FIRE DESIGN<br />
Table M16.2-4 Design Load Ratios for Compression Members Exposed on Three<br />
Sides<br />
(Structural Calculations at Standard Reference Conditions: C M = 1.0, C t = 1.0, C i = 1.0)<br />
(Protected Surface in Width Direction)<br />
Table M16.2-4A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-4B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Col. Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Col. Depth Design Load Ratio, R s Col. Depth Design Load Ratio, R s<br />
5.5 0.18 6 0.22<br />
6.875 0.25 0.38 0.14 7.5 0.29 0.42 0.17<br />
8.25 0.30 0.45 0.56 0.20 0.28 0.12 9 0.33 0.48 0.61 0.22 0.32 0.16<br />
9.625 0.33 0.50 0.62 0.72 0.24 0.34 0.43 0.17 0.24 10.5 0.36 0.53 0.67 0.77 0.26 0.37 0.47 0.21 0.28<br />
11 0.36 0.54 0.67 0.78 0.28 0.39 0.49 0.21 0.29 12 0.39 0.56 0.71 0.82 0.29 0.42 0.52 0.25 0.34<br />
12.375 0.38 0.57 0.70 0.82 0.30 0.42 0.53 0.25 0.34 13.5 0.41 0.59 0.75 0.86 0.32 0.45 0.56 0.28 0.38<br />
13.75 0.39 0.59 0.73 0.85 0.32 0.45 0.57 0.27 0.37 15 0.42 0.61 0.77 0.89 0.34 0.48 0.60 0.31 0.41<br />
15.125 0.41 0.61 0.76 0.88 0.34 0.48 0.60 0.29 0.40 16.5 0.43 0.63 0.80 0.92 0.35 0.50 0.62 0.33 0.44<br />
16.5 0.42 0.63 0.78 0.90 0.35 0.50 0.62 0.31 0.43 18 0.44 0.64 0.81 0.94 0.37 0.51 0.65 0.34 0.46<br />
17.875 0.42 0.64 0.79 0.92 0.36 0.51 0.65 0.32 0.45 19.5 0.45 0.65 0.83 0.96 0.38 0.53 0.67 0.36 0.48<br />
19.25 0.43 0.65 0.81 0.94 0.37 0.53 0.66 0.34 0.47 21 0.46 0.66 0.84 0.97 0.39 0.54 0.68 0.37 0.50<br />
20.625 0.44 0.66 0.82 0.95 0.38 0.54 0.68 0.35 0.48 22.5 0.47 0.67 0.85 0.98 0.39 0.55 0.70 0.38 0.51<br />
22 0.45 0.67 0.83 0.97 0.39 0.55 0.69 0.36 0.49 24 0.47 0.68 0.86 1.00 0.40 0.56 0.71 0.39 0.53<br />
23.375 0.45 0.68 0.84 0.98 0.40 0.56 0.70 0.37 0.51 25.5 0.48 0.69 0.87 1.00 0.41 0.57 0.72 0.40 0.54<br />
24.75 0.45 0.68 0.85 0.99 0.40 0.57 0.72 0.37 0.52 27 0.48 0.69 0.88 1.00 0.41 0.58 0.73 0.40 0.55<br />
26.125 0.46 0.69 0.86 1.00 0.41 0.58 0.73 0.38 0.53 28.5 0.48 0.70 0.89 1.00 0.42 0.59 0.74 0.41 0.56<br />
27.5 0.46 0.70 0.86 1.00 0.41 0.58 0.73 0.39 0.53 30 0.49 0.70 0.90 1.00 0.42 0.59 0.75 0.42 0.56<br />
28.875 0.47 0.70 0.87 1.00 0.42 0.59 0.74 0.39 0.54 31.5 0.49 0.71 0.90 1.00 0.43 0.60 0.75 0.42 0.57<br />
30.25 0.47 0.71 0.88 1.00 0.42 0.59 0.75 0.40 0.55 33 0.49 0.71 0.91 1.00 0.43 0.60 0.76 0.43 0.58<br />
31.625 0.47 0.71 0.88 1.00 0.43 0.60 0.75 0.40 0.55 34.5 0.50 0.72 0.91 1.00 0.43 0.61 0.77 0.43 0.58<br />
33 0.47 0.71 0.89 1.00 0.43 0.60 0.76 0.41 0.56 36 0.50 0.72 0.92 1.00 0.44 0.61 0.77 0.44 0.59<br />
34.375 0.48 0.72 0.89 1.00 0.43 0.61 0.77 0.41 0.57 37.5 0.72 0.92 1.00 0.44 0.62 0.78 0.44 0.59<br />
35.75 0.48 0.72 0.89 1.00 0.43 0.61 0.77 0.41 0.57 39 0.73 0.92 1.00 0.44 0.62 0.78 0.44 0.60<br />
37.125 0.72 0.90 1.00 0.44 0.62 0.78 0.42 0.57 40.5 0.73 0.93 1.00 0.44 0.62 0.79 0.45 0.60<br />
38.5 0.73 0.90 1.00 0.44 0.62 0.78 0.42 0.58 42 0.73 0.93 1.00 0.45 0.63 0.79 0.45 0.61<br />
39.875 0.73 0.90 1.00 0.44 0.62 0.78 0.42 0.58 43.5 0.73 0.93 1.00 0.45 0.63 0.79 0.45 0.61<br />
41.25 0.73 0.91 1.00 0.44 0.63 0.79 0.43 0.59 45 0.74 0.94 1.00 0.45 0.63 0.80 0.45 0.61<br />
42.625 0.73 0.91 1.00 0.45 0.63 0.79 0.43 0.59 46.5 0.74 0.94 1.00 0.45 0.64 0.80 0.46 0.62<br />
44 0.74 0.91 1.00 0.45 0.63 0.79 0.43 0.59 48 0.74 0.94 1.00 0.45 0.64 0.80 0.46 0.62<br />
45.375 0.74 0.92 1.00 0.45 0.63 0.80 0.43 0.60 49.5 0.94 1.00 0.45 0.64 0.81 0.46 0.62<br />
46.75 0.74 0.92 1.00 0.45 0.64 0.80 0.43 0.60 51 0.95 1.00 0.46 0.64 0.81 0.46 0.63<br />
48.125 0.74 0.92 1.00 0.45 0.64 0.80 0.44 0.60 52.5 0.95 1.00 0.46 0.64 0.81 0.46 0.63<br />
49.5 0.92 1.00 0.64 0.81 0.44 0.60 54 0.95 1.00 0.65 0.81 0.47 0.63<br />
50.875 0.92 1.00 0.64 0.81 0.44 0.61 55.5 0.95 1.00 0.65 0.82 0.47 0.63<br />
52.25 0.93 1.00 0.64 0.81 0.44 0.61 57 0.95 1.00 0.65 0.82 0.47 0.63<br />
53.625 0.93 1.00 0.65 0.81 0.44 0.61 58.5 0.95 1.00 0.65 0.82 0.47 0.64<br />
55 0.93 1.00 0.65 0.82 0.44 0.61 60 0.96 1.00 0.65 0.82 0.47 0.64<br />
56.375 0.93 1.00 0.65 0.82 0.45 0.62 61.5 0.96 1.00 0.65 0.82 0.47 0.64<br />
57.75 0.93 1.00 0.65 0.82 0.45 0.62 63 0.96 1.00 0.66 0.83 0.48 0.64<br />
59.125 0.93 1.00 0.65 0.82 0.45 0.62 64.5 1.00 0.66 0.83 0.64<br />
60.5 0.94 1.00 0.65 0.82 0.45 0.62 66 1.00 0.66 0.83 0.65<br />
61.875 0.94 1.00 0.66 0.82 0.45 0.62 67.5 1.00 0.66 0.83 0.65<br />
63.25 0.94 1.00 0.66 0.83 0.45 0.62 69 1.00 0.66 0.83 0.65<br />
64.625 1.00 0.83 0.62 70.5 1.00 0.83 0.65<br />
66 1.00 0.83 0.63 72 1.00 0.83 0.65<br />
67.375 1.00 0.83 0.63 73.5 1.00 0.84 0.65<br />
68.75 1.00 0.83 0.63 75 1.00 0.84 0.65<br />
70.125 1.00 0.83 0.63 76.5 1.00 0.84 0.65<br />
71.5 1.00 0.83 0.63 78 1.00 0.84 0.66<br />
72.875 1.00 0.84 0.63 79.5 1.00 0.84 0.66<br />
74.25 1.00 0.84 0.63 81 1.00 0.84 0.66<br />
75.625 1.00 0.84 0.63<br />
77 1.00 0.84 0.64<br />
Table M16.2-4C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Col. Depth<br />
Design Load Ratio, R s<br />
5.5 0.21<br />
7.5 0.32 0.46 0.20<br />
9.5 0.38 0.55 0.67 0.28 0.38 0.20<br />
11.5 0.42 0.61 0.74 0.84 0.34 0.46 0.55 0.27 0.35<br />
13.5 0.45 0.65 0.79 0.89 0.38 0.51 0.61 0.32 0.41<br />
15.5 0.47 0.68 0.83 0.94 0.41 0.55 0.66 0.36 0.46<br />
17.5 0.49 0.71 0.86 0.97 0.43 0.58 0.69 0.38 0.49<br />
19.5 0.50 0.73 0.88 0.99 0.45 0.60 0.72 0.41 0.52<br />
21.5 0.51 0.74 0.90 1.00 0.46 0.62 0.75 0.43 0.55<br />
23.5 0.52 0.75 0.92 1.00 0.47 0.64 0.77 0.44 0.57<br />
Notes:<br />
1. Tabulated values assume bending in the width direction.<br />
2. Tabulated values conservatively assume column buckling failure. For relatively<br />
short, highly loaded columns, a more rigorous analysis using the NDS<br />
provisions will increase the design load ratio, R s .<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
151<br />
Table M16.2-5 Design Load Ratios for Compression Members Exposed on Four<br />
Sides<br />
(Structural Calculations at Standard Reference Conditions: C M = 1.0, C t = 1.0, C i = 1.0)<br />
Table M16.2-5A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-5B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Col. Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Col. Depth Design Load Ratio, R s Col. Depth Design Load Ratio, R s<br />
5.5 0.02 6 0.02<br />
6.875 0.02 0.10 0.01 7.5 0.03 0.11 0.01<br />
8.25 0.03 0.12 0.22 0.01 0.06 0.01 9 0.03 0.12 0.25 0.02 0.06 0.01<br />
9.625 0.03 0.13 0.24 0.36 0.02 0.07 0.14 0.01 0.04 10.5 0.04 0.14 0.27 0.39 0.02 0.07 0.15 0.02 0.06<br />
11 0.03 0.14 0.26 0.39 0.02 0.08 0.16 0.01 0.05 12 0.04 0.14 0.29 0.42 0.02 0.08 0.17 0.02 0.07<br />
12.375 0.03 0.15 0.28 0.41 0.02 0.08 0.17 0.02 0.06 13.5 0.04 0.15 0.30 0.44 0.02 0.09 0.18 0.02 0.08<br />
13.75 0.03 0.15 0.29 0.43 0.02 0.09 0.18 0.02 0.07 15 0.04 0.16 0.31 0.45 0.02 0.09 0.19 0.03 0.08<br />
15.125 0.03 0.16 0.30 0.44 0.02 0.09 0.19 0.02 0.07 16.5 0.04 0.16 0.32 0.47 0.02 0.10 0.20 0.03 0.09<br />
16.5 0.03 0.16 0.30 0.45 0.02 0.10 0.20 0.02 0.08 18 0.04 0.17 0.33 0.48 0.03 0.10 0.21 0.03 0.09<br />
17.875 0.04 0.16 0.31 0.46 0.03 0.10 0.21 0.02 0.08 19.5 0.04 0.17 0.34 0.49 0.03 0.10 0.22 0.03 0.10<br />
19.25 0.04 0.17 0.32 0.47 0.03 0.10 0.22 0.02 0.09 21 0.04 0.17 0.34 0.49 0.03 0.11 0.22 0.03 0.10<br />
20.625 0.04 0.17 0.32 0.48 0.03 0.11 0.22 0.02 0.09 22.5 0.04 0.17 0.35 0.50 0.03 0.11 0.23 0.03 0.10<br />
22 0.04 0.17 0.33 0.48 0.03 0.11 0.22 0.02 0.09 24 0.05 0.18 0.35 0.51 0.03 0.11 0.23 0.03 0.10<br />
23.375 0.04 0.17 0.33 0.49 0.03 0.11 0.23 0.02 0.09 25.5 0.05 0.18 0.36 0.51 0.03 0.11 0.23 0.03 0.11<br />
24.75 0.04 0.18 0.33 0.49 0.03 0.11 0.23 0.03 0.10 27 0.05 0.18 0.36 0.52 0.03 0.11 0.24 0.03 0.11<br />
26.125 0.04 0.18 0.34 0.50 0.03 0.11 0.24 0.03 0.10 28.5 0.05 0.18 0.36 0.52 0.03 0.12 0.24 0.03 0.11<br />
27.5 0.04 0.18 0.34 0.50 0.03 0.12 0.24 0.03 0.10 30 0.05 0.18 0.36 0.53 0.03 0.12 0.24 0.03 0.11<br />
28.875 0.04 0.18 0.34 0.50 0.03 0.12 0.24 0.03 0.10 31.5 0.05 0.18 0.37 0.53 0.03 0.12 0.24 0.03 0.11<br />
30.25 0.04 0.18 0.34 0.51 0.03 0.12 0.24 0.03 0.10 33 0.05 0.18 0.37 0.53 0.03 0.12 0.25 0.03 0.11<br />
31.625 0.04 0.18 0.34 0.51 0.03 0.12 0.24 0.03 0.10 34.5 0.05 0.18 0.37 0.53 0.03 0.12 0.25 0.04 0.12<br />
33 0.04 0.18 0.35 0.51 0.03 0.12 0.25 0.03 0.10 36 0.05 0.19 0.37 0.54 0.03 0.12 0.25 0.04 0.12<br />
34.375 0.04 0.18 0.35 0.52 0.03 0.12 0.25 0.03 0.10 37.5 0.19 0.37 0.54 0.03 0.12 0.25 0.04 0.12<br />
35.75 0.04 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 39 0.19 0.38 0.54 0.03 0.12 0.25 0.04 0.12<br />
37.125 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 40.5 0.19 0.38 0.54 0.03 0.12 0.25 0.04 0.12<br />
38.5 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 42 0.19 0.38 0.55 0.03 0.12 0.26 0.04 0.12<br />
39.875 0.19 0.35 0.52 0.03 0.12 0.25 0.03 0.11 43.5 0.19 0.38 0.55 0.03 0.12 0.26 0.04 0.12<br />
41.25 0.19 0.35 0.53 0.03 0.12 0.26 0.03 0.11 45 0.19 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
42.625 0.19 0.36 0.53 0.03 0.12 0.26 0.03 0.11 46.5 0.19 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
44 0.19 0.36 0.53 0.03 0.12 0.26 0.03 0.11 48 0.19 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
45.375 0.19 0.36 0.53 0.03 0.13 0.26 0.03 0.11 49.5 0.38 0.55 0.03 0.13 0.26 0.04 0.12<br />
46.75 0.19 0.36 0.53 0.03 0.13 0.26 0.03 0.11 51 0.38 0.56 0.03 0.13 0.26 0.04 0.12<br />
48.125 0.19 0.36 0.53 0.03 0.13 0.26 0.03 0.11 52.5 0.39 0.56 0.03 0.13 0.26 0.04 0.12<br />
49.5 0.36 0.53 0.13 0.26 0.03 0.11 54 0.39 0.56 0.13 0.26 0.04 0.13<br />
50.875 0.36 0.54 0.13 0.26 0.03 0.11 55.5 0.39 0.56 0.13 0.26 0.04 0.13<br />
52.25 0.36 0.54 0.13 0.26 0.03 0.11 57 0.39 0.56 0.13 0.27 0.04 0.13<br />
53.625 0.36 0.54 0.13 0.26 0.03 0.11 58.5 0.39 0.56 0.13 0.27 0.04 0.13<br />
55 0.36 0.54 0.13 0.26 0.03 0.11 60 0.39 0.56 0.13 0.27 0.04 0.13<br />
56.375 0.36 0.54 0.13 0.27 0.03 0.11 61.5 0.39 0.56 0.13 0.27 0.04 0.13<br />
57.75 0.36 0.54 0.13 0.27 0.03 0.11 63 0.39 0.56 0.13 0.27 0.04 0.13<br />
59.125 0.37 0.54 0.13 0.27 0.03 0.11 64.5 0.56 0.13 0.27 0.13<br />
60.5 0.37 0.54 0.13 0.27 0.03 0.11 66 0.56 0.13 0.27 0.13<br />
61.875 0.37 0.54 0.13 0.27 0.03 0.11 67.5 0.57 0.13 0.27 0.13<br />
63.25 0.37 0.54 0.13 0.27 0.03 0.11 69 0.57 0.13 0.27 0.13<br />
64.625 0.54 0.27 0.12 70.5 0.57 0.27 0.13<br />
66 0.54 0.27 0.12 72 0.57 0.27 0.13<br />
67.375 0.55 0.27 0.12 73.5 0.57 0.27 0.13<br />
68.75 0.55 0.27 0.12 75 0.57 0.27 0.13<br />
70.125 0.55 0.27 0.12 76.5 0.57 0.27 0.13<br />
71.5 0.55 0.27 0.12 78 0.57 0.27 0.13<br />
72.875 0.55 0.27 0.12 79.5 0.57 0.27 0.13<br />
74.25 0.55 0.27 0.12 81 0.57 0.27 0.13<br />
75.625 0.55 0.27 0.12<br />
77 0.55 0.27 0.12<br />
Table M16.2-5C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Col. Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Col. Depth<br />
Design Load Ratio, R s<br />
5.5 0.03<br />
7.5 0.04 0.15 0.02<br />
9.5 0.05 0.18 0.30 0.04 0.10 0.03<br />
11.5 0.06 0.20 0.33 0.45 0.04 0.12 0.21 0.03 0.08<br />
13.5 0.06 0.21 0.36 0.48 0.05 0.14 0.23 0.04 0.10<br />
15.5 0.06 0.22 0.37 0.51 0.05 0.15 0.25 0.04 0.11<br />
17.5 0.07 0.23 0.39 0.52 0.05 0.15 0.26 0.05 0.12<br />
19.5 0.07 0.23 0.40 0.54 0.06 0.16 0.27 0.05 0.13<br />
21.5 0.07 0.24 0.40 0.55 0.06 0.16 0.28 0.05 0.13<br />
23.5 0.07 0.24 0.41 0.56 0.06 0.17 0.29 0.06 0.14<br />
Notes:<br />
1. Tabulated values assume bending in the width direction.<br />
2. Tabulated values conservatively assume column buckling failure. For relatively<br />
short, highly loaded columns, a more rigorous analysis using the NDS<br />
provisions will increase the design load ratio, R s .<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
152 M16: FIRE DESIGN<br />
Table M16.2-6 Design Load Ratios for Tension Members Exposed on Three Sides<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)<br />
(Protected Surface in Depth Direction)<br />
Table M16.2-6A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-6B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Beam Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Beam Depth Design Load Ratio, R s Beam Depth Design Load Ratio, R s<br />
5.5 0.54 0.89 1.00 1.00 0.40 0.64 0.81 0.31 0.48 6 0.59 0.93 1.00 1.00 0.43 0.71 0.89 0.37 0.55<br />
6.875 0.59 0.98 1.00 1.00 0.47 0.75 0.95 0.39 0.61 7.5 0.64 1.00 1.00 1.00 0.49 0.81 1.00 0.46 0.68<br />
8.25 0.62 1.00 1.00 1.00 0.51 0.82 1.00 0.45 0.70 9 0.68 1.00 1.00 1.00 0.53 0.88 1.00 0.51 0.76<br />
9.625 0.65 1.00 1.00 1.00 0.54 0.87 1.00 0.49 0.76 10.5 0.70 1.00 1.00 1.00 0.56 0.93 1.00 0.55 0.82<br />
11 0.67 1.00 1.00 1.00 0.57 0.91 1.00 0.52 0.81 12 0.72 1.00 1.00 1.00 0.58 0.97 1.00 0.58 0.86<br />
12.375 0.68 1.00 1.00 1.00 0.59 0.93 1.00 0.54 0.84 13.5 0.73 1.00 1.00 1.00 0.60 0.99 1.00 0.60 0.90<br />
13.75 0.69 1.00 1.00 1.00 0.60 0.96 1.00 0.56 0.87 15 0.75 1.00 1.00 1.00 0.61 1.00 1.00 0.62 0.93<br />
15.125 0.70 1.00 1.00 1.00 0.61 0.98 1.00 0.58 0.90 16.5 0.76 1.00 1.00 1.00 0.62 1.00 1.00 0.64 0.95<br />
16.5 0.71 1.00 1.00 1.00 0.62 0.99 1.00 0.59 0.92 18 0.76 1.00 1.00 1.00 0.63 1.00 1.00 0.65 0.97<br />
17.875 0.72 1.00 1.00 1.00 0.63 1.00 1.00 0.60 0.93 19.5 0.77 1.00 1.00 1.00 0.64 1.00 1.00 0.66 0.98<br />
19.25 0.72 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.95 21 0.78 1.00 1.00 1.00 0.65 1.00 1.00 0.67 1.00<br />
20.625 0.73 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.96 22.5 0.78 1.00 1.00 1.00 0.65 1.00 1.00 0.68 1.00<br />
22 0.73 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.97 24 0.78 1.00 1.00 1.00 0.66 1.00 1.00 0.69 1.00<br />
23.375 0.74 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 25.5 0.79 1.00 1.00 1.00 0.66 1.00 1.00 0.69 1.00<br />
24.75 0.74 1.00 1.00 1.00 0.66 1.00 1.00 0.64 0.99 27 0.79 1.00 1.00 1.00 0.67 1.00 1.00 0.70 1.00<br />
26.125 0.74 1.00 1.00 1.00 0.67 1.00 1.00 0.64 1.00 28.5 0.79 1.00 1.00 1.00 0.67 1.00 1.00 0.70 1.00<br />
27.5 0.75 1.00 1.00 1.00 0.67 1.00 1.00 0.65 1.00 30 0.80 1.00 1.00 1.00 0.68 1.00 1.00 0.71 1.00<br />
28.875 0.75 1.00 1.00 1.00 0.67 1.00 1.00 0.65 1.00 31.5 0.80 1.00 1.00 1.00 0.68 1.00 1.00 0.71 1.00<br />
30.25 0.75 1.00 1.00 1.00 0.68 1.00 1.00 0.65 1.00 33 0.80 1.00 1.00 1.00 0.68 1.00 1.00 0.71 1.00<br />
31.625 0.75 1.00 1.00 1.00 0.68 1.00 1.00 0.66 1.00 34.5 0.80 1.00 1.00 1.00 0.68 1.00 1.00 0.72 1.00<br />
33 0.75 1.00 1.00 1.00 0.68 1.00 1.00 0.66 1.00 36 0.81 1.00 1.00 1.00 0.69 1.00 1.00 0.72 1.00<br />
34.375 0.76 1.00 1.00 1.00 0.68 1.00 1.00 0.66 1.00 37.5 1.00 1.00 1.00 0.69 1.00 1.00 0.72 1.00<br />
35.75 0.76 1.00 1.00 1.00 0.68 1.00 1.00 0.66 1.00 39 1.00 1.00 1.00 0.69 1.00 1.00 0.73 1.00<br />
37.125 1.00 1.00 1.00 0.69 1.00 1.00 0.67 1.00 40.5 1.00 1.00 1.00 0.69 1.00 1.00 0.73 1.00<br />
38.5 1.00 1.00 1.00 0.69 1.00 1.00 0.67 1.00 42 1.00 1.00 1.00 0.69 1.00 1.00 0.73 1.00<br />
39.875 1.00 1.00 1.00 0.69 1.00 1.00 0.67 1.00 43.5 1.00 1.00 1.00 0.69 1.00 1.00 0.73 1.00<br />
41.25 1.00 1.00 1.00 0.69 1.00 1.00 0.67 1.00 45 1.00 1.00 1.00 0.70 1.00 1.00 0.73 1.00<br />
42.625 1.00 1.00 1.00 0.69 1.00 1.00 0.68 1.00 46.5 1.00 1.00 1.00 0.70 1.00 1.00 0.74 1.00<br />
44 1.00 1.00 1.00 0.69 1.00 1.00 0.68 1.00 48 1.00 1.00 1.00 0.70 1.00 1.00 0.74 1.00<br />
45.375 1.00 1.00 1.00 0.70 1.00 1.00 0.68 1.00 49.5 1.00 1.00 1.00 1.00 0.74 1.00<br />
46.75 1.00 1.00 1.00 0.70 1.00 1.00 0.68 1.00 51 1.00 1.00 1.00 1.00 0.74 1.00<br />
48.125 1.00 1.00 1.00 0.70 1.00 1.00 0.68 1.00 52.5 1.00 1.00 1.00 1.00 0.74 1.00<br />
49.5 1.00 1.00 1.00 1.00 0.68 1.00 54 1.00 1.00 1.00 1.00 0.74 1.00<br />
50.875 1.00 1.00 1.00 1.00 0.68 1.00 55.5 1.00 1.00 1.00 1.00 0.74 1.00<br />
52.25 1.00 1.00 1.00 1.00 0.69 1.00 57 1.00 1.00 1.00 1.00 0.75 1.00<br />
53.625 1.00 1.00 1.00 1.00 0.69 1.00 58.5 1.00 1.00 1.00 1.00 0.75 1.00<br />
55 1.00 1.00 1.00 1.00 0.69 1.00 60 1.00 1.00 1.00 1.00 0.75 1.00<br />
56.375 1.00 1.00 1.00 1.00 0.69 1.00 61.5 1.00 1.00 1.00 1.00 0.75 1.00<br />
57.75 1.00 1.00 1.00 1.00 0.69 1.00 63 1.00 1.00 1.00 1.00 0.75 1.00<br />
59.125 1.00 1.00 1.00 1.00 0.69 1.00 64.5 1.00 1.00 1.00<br />
60.5 1.00 1.00 1.00 1.00 0.69 1.00 66 1.00 1.00 1.00<br />
61.875 1.00 1.00 1.00 1.00 0.69 1.00 67.5 1.00 1.00 1.00<br />
63.25 1.00 1.00 1.00 1.00 0.69 1.00 69 1.00 1.00 1.00<br />
64.625 1.00 1.00 1.00 70.5 1.00 1.00 1.00<br />
66 1.00 1.00 1.00 72 1.00 1.00 1.00<br />
67.375 1.00 1.00 1.00 73.5 1.00 1.00 1.00<br />
68.75 1.00 1.00 1.00 75 1.00 1.00 1.00<br />
70.125 1.00 1.00 1.00 76.5 1.00 1.00 1.00<br />
71.5 1.00 1.00 1.00 78 1.00 1.00 1.00<br />
72.875 1.00 1.00 1.00 79.5 1.00 1.00 1.00<br />
74.25 1.00 1.00 1.00 81 1.00 1.00 1.00<br />
75.625 1.00 1.00 1.00<br />
77 1.00 1.00 1.00<br />
Table M16.2-6C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Beam Depth<br />
Design Load Ratio, R s<br />
5.5 0.66 1.00 1.00 1.00 0.52 0.73 0.88 0.40 0.55<br />
7.5 0.75 1.00 1.00 1.00 0.63 0.90 1.00 0.55 0.74<br />
9.5 0.80 1.00 1.00 1.00 0.70 0.99 1.00 0.64 0.86<br />
11.5 0.83 1.00 1.00 1.00 0.74 1.00 1.00 0.69 0.93<br />
13.5 0.85 1.00 1.00 1.00 0.77 1.00 1.00 0.73 0.98<br />
15.5 0.87 1.00 1.00 1.00 0.79 1.00 1.00 0.76 1.00<br />
17.5 0.88 1.00 1.00 1.00 0.81 1.00 1.00 0.78 1.00<br />
19.5 0.89 1.00 1.00 1.00 0.83 1.00 1.00 0.80 1.00<br />
21.5 0.90 1.00 1.00 1.00 0.84 1.00 1.00 0.81 1.00<br />
23.5 0.91 1.00 1.00 1.00 0.85 1.00 1.00 0.82 1.00<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
153<br />
Table M16.2-7 Design Load Ratios for Tension Members Exposed on Three Sides<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)<br />
(Protected Surface in Width Direction)<br />
Table M16.2-7A Southern Pine Glued Structural Laminated<br />
Timbers<br />
Table M16.2-7B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Beam Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Beam Depth Design Load Ratio, R s Beam Depth Design Load Ratio, R s<br />
5.5 0.63 0.72 0.78 0.82 0.16 0.18 0.20 6 0.74 0.84 0.91 0.95 0.30 0.34 0.36<br />
6.875 0.87 1.00 1.00 1.00 0.49 0.55 0.59 0.14 0.16 7.5 0.96 1.00 1.00 1.00 0.60 0.68 0.73 0.29 0.32<br />
8.25 1.00 1.00 1.00 1.00 0.71 0.79 0.85 0.42 0.46 9 1.00 1.00 1.00 1.00 0.80 0.90 0.97 0.54 0.60<br />
9.625 1.00 1.00 1.00 1.00 0.86 0.97 1.00 0.61 0.68 10.5 1.00 1.00 1.00 1.00 0.94 1.00 1.00 0.72 0.80<br />
11 1.00 1.00 1.00 1.00 0.98 1.00 1.00 0.76 0.85 12 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.86 0.95<br />
12.375 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.87 0.97 13.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.97 1.00<br />
13.75 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.97 1.00 15 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
15.125 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 16.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
16.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 18 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
17.875 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 19.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
19.25 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 21 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
20.625 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 22.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
22 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 24 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
23.375 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 25.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
24.75 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 27 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
26.125 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 28.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
27.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 30 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
28.875 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 31.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
30.25 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 33 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
31.625 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 34.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
33 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 36 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
34.375 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 37.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
35.75 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 39 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
37.125 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 40.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
38.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 42 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
39.875 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 43.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
41.25 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 45 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
42.625 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 46.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
44 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 48 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
45.375 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 49.5 1.00 1.00 1.00 1.00 1.00 1.00<br />
46.75 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 51 1.00 1.00 1.00 1.00 1.00 1.00<br />
48.125 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 52.5 1.00 1.00 1.00 1.00 1.00 1.00<br />
49.5 1.00 1.00 1.00 1.00 1.00 1.00 54 1.00 1.00 1.00 1.00 1.00 1.00<br />
50.875 1.00 1.00 1.00 1.00 1.00 1.00 55.5 1.00 1.00 1.00 1.00 1.00 1.00<br />
52.25 1.00 1.00 1.00 1.00 1.00 1.00 57 1.00 1.00 1.00 1.00 1.00 1.00<br />
53.625 1.00 1.00 1.00 1.00 1.00 1.00 58.5 1.00 1.00 1.00 1.00 1.00 1.00<br />
55 1.00 1.00 1.00 1.00 1.00 1.00 60 1.00 1.00 1.00 1.00 1.00 1.00<br />
56.375 1.00 1.00 1.00 1.00 1.00 1.00 61.5 1.00 1.00 1.00 1.00 1.00 1.00<br />
57.75 1.00 1.00 1.00 1.00 1.00 1.00 63 1.00 1.00 1.00 1.00 1.00 1.00<br />
59.125 1.00 1.00 1.00 1.00 1.00 1.00 64.5 1.00 1.00 1.00<br />
60.5 1.00 1.00 1.00 1.00 1.00 1.00 66 1.00 1.00 1.00<br />
61.875 1.00 1.00 1.00 1.00 1.00 1.00 67.5 1.00 1.00 1.00<br />
63.25 1.00 1.00 1.00 1.00 1.00 1.00 69 1.00 1.00 1.00<br />
64.625 1.00 1.00 1.00 70.5 1.00 1.00 1.00<br />
66 1.00 1.00 1.00 72 1.00 1.00 1.00<br />
67.375 1.00 1.00 1.00 73.5 1.00 1.00 1.00<br />
68.75 1.00 1.00 1.00 75 1.00 1.00 1.00<br />
70.125 1.00 1.00 1.00 76.5 1.00 1.00 1.00<br />
71.5 1.00 1.00 1.00 78 1.00 1.00 1.00<br />
72.875 1.00 1.00 1.00 79.5 1.00 1.00 1.00<br />
74.25 1.00 1.00 1.00 81 1.00 1.00 1.00<br />
75.625 1.00 1.00 1.00<br />
77 1.00 1.00 1.00<br />
Table M16.2-7C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Beam Depth<br />
Design Load Ratio, R s<br />
5.5 0.66 0.75 0.80 0.83 0.17 0.19 0.20<br />
7.5 1.00 1.00 1.00 1.00 0.63 0.70 0.74 0.30 0.32<br />
9.5 1.00 1.00 1.00 1.00 0.90 0.99 1.00 0.64 0.69<br />
11.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 0.86 0.93<br />
13.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
15.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
17.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
19.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
21.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
23.5 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
154 M16: FIRE DESIGN<br />
Table M16.2-8 Design Load Ratios for Tension Members Exposed on Four Sides<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)<br />
Table M16.2-8A Southern Pine Structural Glued Laminated<br />
Timbers<br />
Table M16.2-8B Western Species Structural Glued Laminated<br />
Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5 6.75 8.5 10.5 6.75 8.5 10.5 8.5 10.5 Beam Width 5.125 6.75 8.75 10.75 6.75 8.75 10.75 8.75 10.75<br />
Beam Depth Design Load Ratio, R s Beam Depth Design Load Ratio, R s<br />
5.5 0.28 0.46 0.57 0.65 0.07 0.11 0.13 6 0.34 0.53 0.67 0.76 0.12 0.20 0.25<br />
6.875 0.38 0.63 0.78 0.89 0.20 0.32 0.41 0.06 0.09 7.5 0.44 0.69 0.87 0.99 0.24 0.41 0.51 0.12 0.18<br />
8.25 0.45 0.75 0.93 1.00 0.29 0.46 0.59 0.17 0.26 9 0.51 0.80 1.00 1.00 0.33 0.54 0.68 0.23 0.35<br />
9.625 0.50 0.83 1.00 1.00 0.35 0.56 0.72 0.25 0.39 10.5 0.56 0.87 1.00 1.00 0.39 0.64 0.80 0.31 0.47<br />
11 0.54 0.89 1.00 1.00 0.40 0.64 0.81 0.31 0.48 12 0.59 0.93 1.00 1.00 0.43 0.71 0.89 0.37 0.55<br />
12.375 0.57 0.94 1.00 1.00 0.44 0.70 0.89 0.36 0.55 13.5 0.62 0.98 1.00 1.00 0.46 0.77 0.96 0.42 0.62<br />
13.75 0.59 0.98 1.00 1.00 0.47 0.75 0.95 0.39 0.61 15 0.64 1.00 1.00 1.00 0.49 0.81 1.00 0.46 0.68<br />
15.125 0.61 1.00 1.00 1.00 0.49 0.78 1.00 0.42 0.66 16.5 0.66 1.00 1.00 1.00 0.51 0.85 1.00 0.49 0.72<br />
16.5 0.62 1.00 1.00 1.00 0.51 0.82 1.00 0.45 0.70 18 0.68 1.00 1.00 1.00 0.53 0.88 1.00 0.51 0.76<br />
17.875 0.64 1.00 1.00 1.00 0.53 0.84 1.00 0.47 0.73 19.5 0.69 1.00 1.00 1.00 0.55 0.91 1.00 0.53 0.79<br />
19.25 0.65 1.00 1.00 1.00 0.54 0.87 1.00 0.49 0.76 21 0.70 1.00 1.00 1.00 0.56 0.93 1.00 0.55 0.82<br />
20.625 0.66 1.00 1.00 1.00 0.56 0.89 1.00 0.51 0.79 22.5 0.71 1.00 1.00 1.00 0.57 0.95 1.00 0.57 0.84<br />
22 0.67 1.00 1.00 1.00 0.57 0.91 1.00 0.52 0.81 24 0.72 1.00 1.00 1.00 0.58 0.97 1.00 0.58 0.86<br />
23.375 0.68 1.00 1.00 1.00 0.58 0.92 1.00 0.53 0.83 25.5 0.73 1.00 1.00 1.00 0.59 0.98 1.00 0.59 0.88<br />
24.75 0.68 1.00 1.00 1.00 0.59 0.93 1.00 0.54 0.84 27 0.73 1.00 1.00 1.00 0.60 0.99 1.00 0.60 0.90<br />
26.125 0.69 1.00 1.00 1.00 0.60 0.95 1.00 0.55 0.86 28.5 0.74 1.00 1.00 1.00 0.61 1.00 1.00 0.61 0.91<br />
27.5 0.69 1.00 1.00 1.00 0.60 0.96 1.00 0.56 0.87 30 0.75 1.00 1.00 1.00 0.61 1.00 1.00 0.62 0.93<br />
28.875 0.70 1.00 1.00 1.00 0.61 0.97 1.00 0.57 0.89 31.5 0.75 1.00 1.00 1.00 0.62 1.00 1.00 0.63 0.94<br />
30.25 0.70 1.00 1.00 1.00 0.61 0.98 1.00 0.58 0.90 33 0.76 1.00 1.00 1.00 0.62 1.00 1.00 0.64 0.95<br />
31.625 0.71 1.00 1.00 1.00 0.62 0.99 1.00 0.58 0.91 34.5 0.76 1.00 1.00 1.00 0.63 1.00 1.00 0.65 0.96<br />
33 0.71 1.00 1.00 1.00 0.62 0.99 1.00 0.59 0.92 36 0.76 1.00 1.00 1.00 0.63 1.00 1.00 0.65 0.97<br />
34.375 0.71 1.00 1.00 1.00 0.63 1.00 1.00 0.60 0.92 37.5 1.00 1.00 1.00 0.64 1.00 1.00 0.66 0.98<br />
35.75 0.72 1.00 1.00 1.00 0.63 1.00 1.00 0.60 0.93 39 1.00 1.00 1.00 0.64 1.00 1.00 0.66 0.98<br />
37.125 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.94 40.5 1.00 1.00 1.00 0.65 1.00 1.00 0.67 0.99<br />
38.5 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.95 42 1.00 1.00 1.00 0.65 1.00 1.00 0.67 1.00<br />
39.875 1.00 1.00 1.00 0.64 1.00 1.00 0.61 0.95 43.5 1.00 1.00 1.00 0.65 1.00 1.00 0.68 1.00<br />
41.25 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.96 45 1.00 1.00 1.00 0.65 1.00 1.00 0.68 1.00<br />
42.625 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.97 46.5 1.00 1.00 1.00 0.66 1.00 1.00 0.68 1.00<br />
44 1.00 1.00 1.00 0.65 1.00 1.00 0.62 0.97 48 1.00 1.00 1.00 0.66 1.00 1.00 0.69 1.00<br />
45.375 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 49.5 1.00 1.00 1.00 1.00 0.69 1.00<br />
46.75 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 51 1.00 1.00 1.00 1.00 0.69 1.00<br />
48.125 1.00 1.00 1.00 0.66 1.00 1.00 0.63 0.98 52.5 1.00 1.00 1.00 1.00 0.69 1.00<br />
49.5 1.00 1.00 1.00 1.00 0.64 0.99 54 1.00 1.00 1.00 1.00 0.70 1.00<br />
50.875 1.00 1.00 1.00 1.00 0.64 0.99 55.5 1.00 1.00 1.00 1.00 0.70 1.00<br />
52.25 1.00 1.00 1.00 1.00 0.64 1.00 57 1.00 1.00 1.00 1.00 0.70 1.00<br />
53.625 1.00 1.00 1.00 1.00 0.64 1.00 58.5 1.00 1.00 1.00 1.00 0.70 1.00<br />
55 1.00 1.00 1.00 1.00 0.65 1.00 60 1.00 1.00 1.00 1.00 0.71 1.00<br />
56.375 1.00 1.00 1.00 1.00 0.65 1.00 61.5 1.00 1.00 1.00 1.00 0.71 1.00<br />
57.75 1.00 1.00 1.00 1.00 0.65 1.00 63 1.00 1.00 1.00 1.00 0.71 1.00<br />
59.125 1.00 1.00 1.00 1.00 0.65 1.00 64.5 1.00 1.00 1.00<br />
60.5 1.00 1.00 1.00 1.00 0.65 1.00 66 1.00 1.00 1.00<br />
61.875 1.00 1.00 1.00 1.00 0.65 1.00 67.5 1.00 1.00 1.00<br />
63.25 1.00 1.00 1.00 1.00 0.66 1.00 69 1.00 1.00 1.00<br />
64.625 1.00 1.00 1.00 70.5 1.00 1.00 1.00<br />
66 1.00 1.00 1.00 72 1.00 1.00 1.00<br />
67.375 1.00 1.00 1.00 73.5 1.00 1.00 1.00<br />
68.75 1.00 1.00 1.00 75 1.00 1.00 1.00<br />
70.125 1.00 1.00 1.00 76.5 1.00 1.00 1.00<br />
71.5 1.00 1.00 1.00 78 1.00 1.00 1.00<br />
72.875 1.00 1.00 1.00 79.5 1.00 1.00 1.00<br />
74.25 1.00 1.00 1.00 81 1.00 1.00 1.00<br />
75.625 1.00 1.00 1.00<br />
77 1.00 1.00 1.00<br />
Table M16.2-8C Solid Sawn Timbers<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Beam Width 5.5 7.5 9.5 11.5 7.5 9.5 11.5 9.5 11.5<br />
Beam Depth<br />
Design Load Ratio, R s<br />
5.5 0.34 0.51 0.61 0.68 0.09 0.12 0.14<br />
7.5 0.51 0.77 0.92 1.00 0.32 0.45 0.54 0.15 0.20<br />
9.5 0.61 0.92 1.00 1.00 0.45 0.64 0.76 0.32 0.43<br />
11.5 0.68 1.00 1.00 1.00 0.54 0.76 0.91 0.43 0.58<br />
13.5 0.72 1.00 1.00 1.00 0.60 0.85 1.00 0.51 0.68<br />
15.5 0.76 1.00 1.00 1.00 0.64 0.91 1.00 0.56 0.76<br />
17.5 0.78 1.00 1.00 1.00 0.68 0.96 1.00 0.61 0.82<br />
19.5 0.80 1.00 1.00 1.00 0.70 1.00 1.00 0.64 0.87<br />
21.5 0.82 1.00 1.00 1.00 0.73 1.00 1.00 0.67 0.91<br />
23.5 0.83 1.00 1.00 1.00 0.75 1.00 1.00 0.70 0.94<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
155<br />
Table M16.2-9 Design Load Ratios for Exposed Timber Decks<br />
Double and Single Tongue & Groove Decking<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Deck Thickness<br />
Design Load Ratio, R s<br />
2.5 0.22 - -<br />
3 0.46 0.08 -<br />
3.5 0.67 0.23 0.03<br />
4 0.86 0.40 0.12<br />
4.5 1.00 0.56 0.25<br />
5 1.00 0.71 0.38<br />
5.5 1.00 0.85 0.51<br />
Table M16.2-10 Design Load Ratios for Exposed Timber Decks<br />
Butt-Joint Timber Decking<br />
(Structural Calculations at Standard Reference Conditions: C D = 1.0, C M = 1.0, C t = 1.0, C i = 1.0)<br />
Rating 1-HOUR 1.5-HOUR 2-HOUR<br />
Decking Width 1.5 2.5 3.5 5.5 2.5 3.5 5.5 3.5 5.5<br />
Decking Depth<br />
Design Load Ratio, R s<br />
2.5 0.05 0.12 0.15 0.18 - - - - -<br />
3 0.09 0.24 0.30 0.36 0.03 0.04 0.05 - -<br />
3.5 0.14 0.35 0.44 0.53 0.08 0.12 0.16 - -<br />
4 0.18 0.45 0.57 0.68 0.14 0.21 0.28 0.02 0.08<br />
4.5 0.21 0.54 0.68 0.80 0.19 0.30 0.39 0.04 0.16<br />
5 0.24 0.61 0.77 0.92 0.24 0.38 0.50 0.06 0.24<br />
5.5 0.27 0.68 0.85 1.00 0.29 0.45 0.59 0.09 0.32<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
156 M16: FIRE DESIGN<br />
Example 16.2-1 Exposed Beam Example - Allowable Stress Design<br />
Douglas-fir glulam beams span L = 18' and are spaced<br />
at s = 6'. The design loads are q live = 100 psf and q dead =<br />
25 psf. Timber decking nailed to the compression edge of<br />
the beams provides lateral bracing. Calculate the required<br />
section dimensions for a 1-hour fire resistance time.<br />
For the structural design of the wood beam, calculate<br />
the maximum induced moment.<br />
Calculate beam load:<br />
w total = s (q dead + q live ) = (6)(25 + 100) = 750 plf<br />
Calculate maximum induced moment:<br />
M max = w total L²/8 = (750)(18)²/8 = 30,375 ft-lbs<br />
Select a 6-3/4" x 13-1/2" 24F visually-graded Douglas-fir<br />
glulam beam with a tabulated bending stress, F b ,<br />
equal to 2,400 psi.<br />
Calculate beam section modulus:<br />
S s = bd 2 /6 = (6.75)(13.5) 2 /6 = 205.0 in. 3<br />
Calculate the adjusted allowable bending stress (assuming<br />
C D = 1.0; C M = 1.0; C t = 1.0; C L = 1.0; C V = 0.98)<br />
F′ b = F b (C D )(C M )(C t )(lesser of C L or C V )<br />
= 2,400 (1.0)(1.0)(1.0)(0.98) = 2,343 psi (NDS 5.3.1)<br />
Calculate design resisting moment:<br />
M′ =F′ b S s = (2,343)(205.0)/12 = 40,032 ft-lbs<br />
Structural Check: M′ ≥ M max<br />
40,032 ft-lbs ≥ 30,375 ft-lbs OK<br />
For the fire design of the wood beam, the loading is<br />
unchanged. Therefore, the maximum induced moment is<br />
unchanged. The fire resistance must be calculated.<br />
Calculate beam section modulus exposed on three sides:<br />
S f = (b – 2a)(d – a) 2 /6 = (6.75 – 3.6)(13.5 – 1.8) 2 /6 = 71.9<br />
in. 3<br />
Calculate the adjusted allowable bending stress<br />
(assuming C D = N/A; C M = N/A; C t = N/A; C L = 1.0;<br />
C V = 0.98) F′ b = F b (lesser of C L or C V )<br />
= 2,400 (0.98) = 2,343 psi (NDS 5.3.1)<br />
Calculate strength resisting moment:<br />
M′ = (2.85) F′ b S f = (2.85)(2,343)(71.9)/12<br />
= 40,010 ft-lbs (NDS 16.2.2)<br />
Fire Check: M′ ≥ M max<br />
40,010 ft-lbs ≥ 30,375 ft-lbs OK<br />
Design Aid<br />
Calculate structural design load ratio:<br />
r s = M max /M′ = 30,375/40,032 = 0.76<br />
Select the maximum design load ratio limit from Table<br />
M16.2-1B or calculate using the following equation:<br />
R<br />
s<br />
2. 85S<br />
f ( 2. 85)( 71. 9)<br />
= = = 1.<br />
00<br />
S C C C ( 205)( 1. 0)( 1. 0)( 1. 0)<br />
s D M t<br />
Fire Check: R s ≥ r s 1.00 ≥ 0.76 OK<br />
Example 16.2-2<br />
Exposed Column Example - Allowable Stress Design<br />
A southern pine glulam column with an effective column<br />
length, < e = 168". The design loads are P snow = 16,000<br />
lbs and P dead = 6,000 lbs. Calculate the required section<br />
dimensions for a 1-hour fire resistance time.<br />
For the structural design of the wood column, calculate<br />
the maximum induced compression stress, f c .<br />
Calculate column load:<br />
P total = P dead + P snow = 8,000 + 16,000 = 22,000 lbs<br />
Select a 8-1/2" x 9-5/8" Combination #48 southern<br />
pine glulam column with a tabulated compression parallel-to-grain<br />
stress, F c , equal to 2,200 psi and a tabulated<br />
modulus of elasticity, E min , equal to 880,000 psi.<br />
Calculate column area:<br />
A s = bd = (9.625)(8.5) = 81.81 in. 2<br />
I s = bd 3 /12 = (9.625)(8.5) 3 /12 = 492.6 in. 4<br />
Calculate the adjusted allowable compression stress<br />
(assuming C D = 1.15; C M = 1.0; C t = 1.0):<br />
E min ′ = E min (C M )(C t ) = 880,000 (1.0)(1.0)<br />
= 880,000 psi (NDS 5.3.1)<br />
F cE = 0.822 E min ′ / (< e /d) 2<br />
= 0.822 (880,000) / (168/8.5) 2 = 1,852 psi (NDS 3.7.1.5)<br />
F* c = F c (C D )(C M )(C t )<br />
= 2,200 (1.15)(1.0)(1.0) = 2,530 psi (NDS 3.7.1.5)<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
157<br />
c = 0.9 for structural glued laminated timbers (NDS 3.7.1.5)<br />
C<br />
P<br />
* *<br />
2<br />
*<br />
c c c<br />
1<br />
= + F ⎡ + ⎤<br />
cE/F 1 F<br />
cE/F −<br />
2c ⎢<br />
⎣ 2c ⎥ − F<br />
cE/F<br />
⎦ c<br />
1<br />
= + 0.<br />
7190<br />
−<br />
2( 0. 9)<br />
⎛1+<br />
0.<br />
7190⎞<br />
0 7190<br />
⎝<br />
⎜<br />
2 0 9 ⎠<br />
⎟ − .<br />
( . ) 0.<br />
9<br />
= 0. 626<br />
(NDS 3.7.1.5)<br />
F′ c = F c * (C p ) = 2,530 (0.626) = 1,583 psi (NDS 5.3.1)<br />
Calculate the resisting column compression capacity:<br />
P′ = F′ c A s = (1,583)(81.81) = 129,469 lbs<br />
Structural Check: P′ ≥ P load<br />
129,469 lbs ≥ 22,000 lbs OK<br />
For the fire design of the wood column, the loading<br />
is unchanged. Therefore, the total load is unchanged. The<br />
fire resistance must be calculated.<br />
Calculate column area, A, and moment of inertia, I, for<br />
column exposed on four sides:<br />
A f = (b – 2a)(d – 2a) = (9.625 – 3.6)(8.5 – 3.6)<br />
= 29.52 in. 2<br />
I f = (b – 2a)(d – 2a) 3 /12 = (9.625 – 3.6)(8.5 – 3.6) 3 /12<br />
= 59.07 in. 4<br />
Calculate the adjusted allowable compression stress<br />
(assuming C D = N/A; C M = N/A; C t = N/A):<br />
2<br />
F cE = (2.03) 0.822 E min ′ / (< e /d) 2<br />
= (2.03)(0.822)(880,000) / (168/(8.5 – 3.6)) 2<br />
= 1,249 psi ft-lbs (NDS 16.2.2)<br />
F* c = (2.58) F c = (2.58)(2,200)<br />
= 5,676 psi ft-lbs (NDS 16.2.2)<br />
F cE /F* c = 1,249/5,676 = 0.22<br />
1<br />
C P<br />
= + 0.<br />
22<br />
−<br />
2( 0. 9)<br />
F′ c = 5,676 (0.214) = 1,216 psi<br />
2<br />
⎛1+<br />
0.<br />
22⎞<br />
⎝<br />
⎜<br />
2 0 9 ⎠<br />
⎟ − 0.<br />
22<br />
0 9<br />
= 0.<br />
214<br />
( . ) .<br />
Calculate the resisting column compression capacity:<br />
P′ = F′ c A f = (1,216)(29.52) = 35,884 lbs<br />
Fire Check: P′ ≥ P load<br />
35,884 lbs ≥ 22,000 lbs OK<br />
Design Aid<br />
Calculate structural design load ratio:<br />
r s = M max /M′ = 22,000/128,043 = 0.17<br />
Select the maximum design load ratio (buckling) limit<br />
from Table M16.2-5A or calculate using the following<br />
equation:<br />
R<br />
s<br />
2. 03I<br />
f ( 2. 03)( 59. 07)<br />
= = = 0.<br />
24<br />
I C C ( 492. 6)( 1. 0)( 1. 0)<br />
s M t<br />
Fire Check: R s ≥ r s 0.24 ≥ 0.17 OK<br />
Example 16.2-3<br />
Exposed Tension Member Example - Allowable Stress Design<br />
Solid sawn Hem-Fir timbers used as heavy timber<br />
truss webs. The total design tension loads from a roof live<br />
and dead load are P total = 3,500 lbs. Calculate the required<br />
section dimensions for a 1-hour fire resistance time.<br />
For the structural design of the wood timber, calculate<br />
the maximum induced tension stress, f t .<br />
Calculate tension load: P total = 3,500 lbs<br />
Select a nominal 6x6 (5-1/2" x 5-1/2") Hem-Fir #2<br />
Posts and Timbers grade with a tabulated tension stress,<br />
F t , equal to 375 psi.<br />
Calculate timber area: A s = bd = (5.5)(5.5) = 30.25 in. 2<br />
Calculate the adjusted allowable tension stress<br />
(assuming C D = 1.25; C M = 1.0; C t = 1.0):<br />
F′ t = F t (C D )(C M )(C t )<br />
= 375 (1.25)(1.0)(1.0) = 469 psi (NDS 4.3.1)<br />
Calculate the resisting tension capacity:<br />
P′ = F′ c As = (469)(30.25) = 13,038 lbs<br />
Structural Check: P′ ≥ P load<br />
14,180 lbs ≥ 3,500 lbs OK<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
158 M16: FIRE DESIGN<br />
For the fire design of the timber tension member,<br />
the loading is unchanged. Therefore, the total load is unchanged.<br />
The fire resistance must be calculated.<br />
Calculate tension member area, A, for member exposed<br />
on four sides:<br />
A f = (b – 2a)(d – 2a) = (5.5 – 3.6)(5.5 – 3.6) = 3.61 in. 2<br />
Calculate the adjusted allowable tension stress<br />
(assuming C D = N/A; C M = N/A; C t = N/A):<br />
F′ t = (2.85) F t = (2.85)(375)<br />
= 1,069 psi ft-lbs (NDS 16.2.2)<br />
Design Aid<br />
Calculate structural design load ratio:<br />
r s = M max /M′ = 3,500/14,180 = 0.25<br />
Select the maximum design load ratio limit from Table<br />
M16.2-8C and divide by the load duration factor, C D , or<br />
calculate using the following equation:<br />
R<br />
s<br />
2. 85Af<br />
( 2. 85)( 3. 61)<br />
= = = 0.<br />
27<br />
A C C C ( 30. 25)( 1. 25)( 1. 0)( 1. 0)<br />
s D M t<br />
Fire Check: R s ≥ r s 0.27 ≥ 0.25 OK<br />
Calculate the resisting tension capacity:<br />
P′ = F′ t A f = (1,069)(3.61) = 3,858 lbs<br />
Fire Check: P′ ≥ P load<br />
3,858 lbs ≥ 3,500 lbs OK<br />
Example 16.2-4<br />
Exposed Deck Example - Allowable Stress Design<br />
Hem-Fir tongue-and-groove timber decking spans<br />
L = 6′. A single layer of 3/4" sheathing is installed over<br />
the decking. The design loads are q live = 40 psf and q dead<br />
= 10 psf.<br />
Calculate deck load:<br />
w total = B(q dead + q live ) = (5.5 in./12 in./ft)(50 psf) = 22.9 plf<br />
Calculate maximum induced moment:<br />
M max = w total L²/8 = (22.9)(6)²/8 = 103 ft-lbs<br />
Select nominal 3x6 (2-1/2" x 5-1/2") Hem-Fir Commercial<br />
decking with a tabulated bending stress, F b , equal<br />
to 1,350 psi (already adjusted by C r ).<br />
Calculate beam section modulus:<br />
S s = bd 2 /6 = (5.5)(2.5) 2 /6 = 5.73 in. 3<br />
Calculate the adjusted allowable bending stress<br />
(assuming C D = 1.0; C M = 1.0; C t = 1.0; C F = 1.04):<br />
F′ b = F b (C D )(C M )(C t )(C F )<br />
= 1,350 (1.0)(1.0)(1.0)(1.04) = 1,404 psi (NDS 4.3.1)<br />
Calculate resisting moment:<br />
M′ =F′ b S s = (1,404)(5.73)/12 = 670 ft-lbs<br />
Structural Check: M′ ≥ M max<br />
670 ft-lbs ≥ 103 ft-lbs OK<br />
For the fire design of the timber deck, the loading is<br />
unchanged. Therefore, the maximum induced moment is<br />
unchanged. The fire resistance must be calculated.<br />
Calculate beam section modulus exposed on one side:<br />
S f = (b)(d – a) 2 /6 = (5.5)(2.5 – 1.8) 2 /6 = 0.45 in. 3<br />
Calculate the adjusted allowable bending stress<br />
(assuming C D = N/A; C M = N/A; C t = N/A; C F = 1.04):<br />
F′ b = F b (C F ) = 1,350 (1.04) = 1,404 psi<br />
Calculate resisting moment:<br />
M′ = (2.85) F b S f = (2.85)(1,404)(0.45)/12<br />
= 150 ft-lbs (NDS 16.2.2)<br />
Fire Check: M′ ≥ M max 150 ft-lbs ≥ 103 ft-lbs OK<br />
Design Aid<br />
Calculate structural design load ratio:<br />
r s = M max /M′ = 103/670 = 0.15<br />
Select the maximum design load ratio limit from Table<br />
M16.2-9 or calculate using the following equation:<br />
R<br />
s<br />
2. 85S<br />
f ( 2. 85)( 0. 45)<br />
= = = 0.<br />
22<br />
S C C C ( 5. 73)( 1. 0)( 1. 0)( 1. 0)<br />
s D M t<br />
Fire Check: R s ≥ r s 0.22 ≥ 0.15 OK<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>ASD</strong>/<strong>LRFD</strong> MANUAL FOR ENGINEERED <strong>Wood</strong> Construction<br />
159<br />
M16.3 <strong>Wood</strong> Connections<br />
Where 1-hour fire endurance is required, connectors<br />
and fasteners must be protected from fire exposure by 1.5"<br />
of wood, fire-rated gypsum board, or any coating approved<br />
for a 1-hour rating. Typical details for commonly used<br />
fasteners and connectors in timber framing are shown in<br />
Figure M16.3-1 through Figure M16.3-6.<br />
Figure M16.3-1 Beam to Column<br />
Connection - Connection<br />
Not Exposed to Fire<br />
Figure M16.3-2 Beam to Column<br />
Connection - Connection<br />
Exposed to Fire Where<br />
Appearance is a Factor<br />
Figure M16.3-3 Ceiling Construction<br />
Figure M16.3-4 Beam to Column<br />
Connection - Connection<br />
Exposed to Fire Where<br />
Appearance is Not a Factor<br />
M16: FIRE DESIGN<br />
16<br />
<strong>American</strong> Forest & paper association
160 M16: FIRE DESIGN<br />
Figure M16.3-5 Column Connections<br />
Covered<br />
Figure M16.3-6 Beam to Girder -<br />
Concealed Connection<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong>
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong><br />
Engineered and Traditional <strong>Wood</strong> Products<br />
AWC Mission Statement<br />
To increase the use of wood by assuring the broad<br />
regulatory acceptance of wood products, developing<br />
design tools and guidelines for wood construction,<br />
and influencing the development of public policies<br />
affecting the use of wood products.
<strong>American</strong> Forest & Paper Association<br />
<strong>American</strong> <strong>Wood</strong> <strong>Council</strong><br />
1111 19th Street, NW<br />
Suite 800<br />
Washington, DC 20036<br />
www.awc.org<br />
awcinfo@afandpa.org<br />
America’s Forest & Paper People ®<br />
Improving Tomorrow’s Environment Today ®<br />
09-08