i

Design of Wood Structures—ASD/LRFD
Donald E. Breyer, P.E.
Professor Emeritus
Department of Engineering Technology
California State Polytechnic University
Pomona, California
Kenneth J. Fridley, Ph.D.
Professor and Head
Department of Civil, Construction, and Environmental Engineering
University of Alabama
Tuscaloosa, Alabama
Kelly E. Cobeen, S.E.
Principal
Cobeen & Associates Structural Engineering
Lafayette, California
David G. Pollock, Ph.D., P.E.
Associate Professor
Department of Civil and Environmental Engineering
Washington State University
Pullman, Washington
Sixth Edition

McGraw-Hill
New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New
Delhi San Juan Seoul Singapore Sydney Toronto


ii


Nomenclature

xiii

Abbreviations

xvi

Chapter 1. Wood Buildings and Design Criteria

1.1

1.1 Introduction

1.1

1.2 Types of Buildings

1.2

1.3 Required and Recommended References

1.4

1.4 Building Codes and Design Criteria

1.7

1.5 ASD and LRFD


2.1 Introduction

2.1

2.2 Dead Loads

2.3

2.3 Live Loads

2.7

2.4 Snow Loads

2.14

2.5 Soil Loads and Hydrostatic Pressure

2.21

2.6 Loads due to Fluids

2.21

2.7 Rain Loads

2.21

2.8 Flood Loads

2.61


iv

2.16 Seismic Forces—Wall Components

2.68

2.17 Load Combinations

2.73

2.18 Serviceability/Deflection Criteria

2.78

2.19 References

2.84

2.20 Problems

2.85

Chapter 3. Behavior of Structures under Loads and Forces

3.1

3.1 Introduction


Chapter 4. Properties of Wood and Lumber Grades

4.1

4.1 Introduction

4.1

4.2 Design Specification

4.2

4.3 Methods of Grading Structural Lumber

4.5

4.4 In-Grade Versus Clear Wood Design Values

4.7

4.5 Species and Species Groups

4.9

4.6 Cellular Makeup

4.11

4.7 Moisture Content and Shrinkage


4.15 Load Duration Factor CD (ASD Only)

4.40

4.16 Time Effect Factor Ȝ (LRFD Only)

4.44

4.17 Size Factor CF

4.45

4.18 Repetitive Member Factor Cr

4.46

4.19 Flat Use Factor Cfu

4.47


4.20 Temperature Factor Ct

4.47

4.21 Incising Factor Ci

4.48


5.1 Introduction

5.1

5.2 Sizes of Glulam Members

5.1


v

5.3 Resawn Glulam

5.4

5.4 Fabrication of Glulams

5.5

5.5 Grades of Glulam Members

5.11

5.6 Adjustment Factors for Glulam

5.16

5.7 Design Problem: Adjusted Design Values

5.19

6.5 Shear

6.29

6.6 Deflection

6.36

6.7 Design Summary

6.38

6.8 Bearing at Supports

6.40

6.9 Design Problem: Sawn Beam

6.47

6.10 Design Problem: Rough-Sawn Beam Using ASD

6.54

6.11 Design Problem: Notched Beam

6.56

6.12 Design Problem: Sawn-Beam Analysis


6.85

6.20 References

6.94

6.21 Problems

6.95

Chapter Axial Forces and Combined Bending and Axial Forces
7.
7.1 Introduction

7.1
7.1


7.2 Axial Tension Members

7.2

7.3 Design Problem: Tension Member

7.7

7.4 Columns

7.11


7.52

7.13 Design Problem: Beam-Column

7.59

7.14 Design Problem: Beam-Column Action in a Stud Wall Using
LRFD

7.64

7.15 Design Problem: Glulam Beam-Column Using ASD

7.73

7.16 Design for Minimum Eccentricity

7.80


vi

7.17 Design Problem: Column with Eccentric Load Using ASD

7.81

7.18 References

7.87


8.13

8.7 Plywood Grades

8.14

8.8 Other Wood Structural Panels

8.17

8.9 Roof Sheathing

8.20

8.10 Design Problem: Roof Sheathing

8.23

8.11 Floor Sheathing

8.27

8.12 Design Problem: Floor Sheathing

8.30

8.13 Wall Sheathing and Siding

8.32


9.16

9.5 Design Problem: Roof Diaphragm

9.20

9.6 Distribution of Lateral Forces in a Shearwall

9.28

9.7 Collector (Strut) Forces

9.32

9.8 Diaphragm Deflections

9.37

9.9 Diaphragms with Interior Shearwalls

9.43

9.10 Interior Shearwalls with Collectors

9.47

9.11 Diaphragm Flexibility

9.51



10.11

10.6 Design Problem: Shearwall

10.13

10.7 Alternate Shearwall Design Methods

10.22

10.8 Anchorage Considerations

10.33

10.9 Vertical (Gravity) Loads

10.34

10.10 Lateral Forces Parallel to a Wall

10.35


vii

10.11 Shearwall Deflection

10.39


11.10

11.5 Dowel Bearing Strength

11.13

11.6 Plastic Hinge in Fastener

11.17

11.7 Yield Limit Mechanisms

11.21

11.8 References

11.26

11.9 Problems

11.26

Chapter 12. Nailed and Stapled Connections

12.1

12.1 Introduction

12.1


12.42

12.10 Design Problem: Laterally Loaded Toenail

12.46

12.11 Design Problem: Laterally Loaded Connection in End Grain

12.50

12.12 Nail Withdrawal Connections

12.52

12.13 Combined Lateral and Withdrawal Loads

12.58

12.14 Spacing Requirements

12.59

12.15 Nailing Schedule

12.63

12.16 References

12.63



13.7 Design Problem: Multiple-Bolt Tension Connection

13.34

13.8 Design Problem: Bolted Chord Splice for Diaphragm

13.40

13.9 Shear Stresses in a Beam at a Connection

13.47

13.10 Design Problem: Bolt Connection for Diagonal Brace

13.49

13.11 Lag Bolt Connections

13.55

13.12 Yield Limit Equations for Lag Bolts

13.59


viii

13.13 Adjustment Factors for Lag Bolts in Shear Connections


14.1 Introduction

14.1

14.2 Connection Details

14.1

14.3 Design Problem: Beam-to-Column Connection

14.19

14.4 Cantilever Beam Hinge Connection

14.27

14.5 Prefabricated Connection Hardware

14.29

14.6 References

14.33

Chapter 15. Diaphragm-to-Shearwall Anchorage

15.1

15.1 Introduction



16.1 Introduction

16.1

16.2 Seismic Forces—Regular Structures

16.1

16.3 Seismic Forces—Irregular Structures

16.3

16.4 Overturning—Background

16.14

16.5 Overturning—Review

16.14

16.6 Overturning—Wind

16.19

16.7 Overturning—Seismic

16.23

16.8 Lateral Analysis of Nonrectangular Buildings


Appendix Sl Units
D.

D.1

Index

I.1


ix

Preface
The purpose of this book is to introduce engineers, technologists, and architects to the design of wood
structures. It is designed to serve either as a text for a course in timber design or as a reference for systematic
self-study of the subject.
The book will lead the reader through the complete design of a wood structure (except for the foundation).
The sequence of the material follows the same general order that it would in actual design:
1. Vertical design loads and lateral forces
2. Design for vertical loads (beams and columns)
3. Design for lateral forces (horizontal diaphragms and shearwalls)
4. Connection design (including the overall tying together of the vertical- and lateral-force-resisting systems)
The need for such an overall approach to the subject became clear from experience gained in teaching
timber design at the undergraduate and graduate levels.
This text pulls together the design of the various elements into a single reference. A large number of
practical design examples are provided throughout the text. Because of their widespread usage, buildings
naturally form the basis of the majority of these examples. However, the principles of member design and
diaphragm design have application to other structures (such as concrete formwork and falsework).
This book relies on practical, current industry literature as the basis for structural design. This includes

composite lumber, structural connections (nails, bolts, screws), and pre-engineered metal connectors. The
Manual was first introduced in 1999 for the 1997 NDS, and has evolved into a comprehensive design support
document.
The International Building Code (IBC) is a product of the International Codes Council (ICC). The ICC
brought together the three regional model building code organizations to develop and administer a single
national building code. The first edition of the IBC was published in 2000, and now nearly all regions of the
U.S. have adopted all or part of the IBC at either the state or local level.
Traditionally, the NDS has been based on the principles of what is termed allowable stress design (ASD).
In ASD allowable stresses of a material are compared to calculated working stresses resulting from service
loads. Recently, the wood industry and design community completed the development of a load and
resistance factor design (LRFD) specification for wood construction. In LRFD, adjusted nominal capacities
(resistance) are compared to the effect of factored loads. The factors are developed for both resistance and
loads such that uncertainty and consequence of failure are explicitly recognized. The LRFD approach to wood
design is now included in the 2005 edition of the NDS. This sixth edition of Design of Wood Structures
presents both ASD and LRFD guidelines as provided in the NDS. In many examples, both ASD and LRFD
approaches are presented to allow the reader a direct, side-by-side comparison of the two methods.


xi

If this book is used as a text for a formal course, an Instructor’s Manual is available. Requests on school
letterhead should be sent to: Civil Engineering Editor, McGraw-Hill Professional, 2 Penn Plaza, New York,
NY 10121-2298.
Questions or comments about the text or examples may be addressed to any of the authors. Direct any
correspondence to:
Prof. Emeritus Donald E. Breyer
Department of Engineering Technology
California State Polytechnic University
3801 West Temple Avenue
Pomona, CA 91768

Lynn, Sarah, and Will
Donald E. Breyer, P.E.
Kenneth J. Fridley, Ph.D.
Kelly E. Cobeen, S.E.
David G. Pollock, Ph.D., P.E.


xiii

Nomenclature
Organizations
AF&PA
American Forest and Paper Association
American Wood Council (AWC)
1111 19th Street, NW, Suite 800
Washington, DC 20036
www.afandpa.org
www.awc.org
AITC
American Institute of Timber Construction
7012 South Revere Parkway, Suite 140
Centennial, CO 80112
www.aitc-glulam.org
ALSC
American Lumber Standard Committee, Inc.
P.O. Box 210
Germantown, MD 20875-0210
www.alsc.org
APA
APA—The Engineered Wood Association

CWC
Canadian Wood Council
99 Bank Street, Suite 400
Ottawa, Ontario, Canada K1P 6B9
www.cwc.ca
CPA–CWC
Composite Panel Association
Composite Wood Council
18922 Premiere Court
Gaithersburg, MD 20879-1574
301-670-0604
www.pbmdf.com


xiv

FPL
U.S. Forest Products Laboratory
USDA Forest Service
One Gifford Pinchot Drive
Madison, WI 53726-2398
www.fpl.fs.fed.us
ICC
International Codes Council
5203 Leesburg Pike
Suite 600
Falls Church, VA 22041
www.iccsafe.org
ISANTA
International Staple, Nail and Tool Association

NSLB
Northern Softwood Lumber Bureau
272 Tuttle Road
P.O. Box 87A
Cumberland Center, ME 04021
www.nelma.org
NWPA
Northwest Wood Products Association
149 SE 9th, #2
Bend, OR 97702


www.nwpa.org
PLIB
Pacific Lumber Inspection Bureau
33442 First Way South, #300
Federal Way, WA 98003-6214
www.plib.org
SEAOC
Structural Engineers Association of California
1414 K Street, Suite 260
Sacramento, CA 95814
www.seaoc.org
SLMA
Southeastern Lumber Manufacturers Association
P.O. Box 1788
Forest Park, GA 30298-1788
www.slma.org
SFPA
Southern Forest Products Association

WRCLA
Western Red Cedar Lumber Association
1501-700 West Pender Street
Vancouver, British Columbia, Canada V6C 1G8
www.wrcla.org
WWPA
Western Wood Products Association
522 Southwest Fifth Avenue, Suite 500
Portland, OR 97204-2122
www.wwpa.org
WIJMA
Wood I-Joist Manufacturing Association
200 East Mallard Drive
Boise, ID 83706
www.i-joist.org
WTCA
Wood Truss Council of America
One WTCA Center
6300 Enterprise Lane
Madison, WI 53719
www.woodtruss.com

Publications
ASCE 7: American Society of Civil Engineers (ASCE). 2006. Minimum Design Loads for Buildings
and Other Structures (ASCE 7-05), ASCE, Reston, VA.
ASD/LRFD American Forest and Paper Association (AF&PA). 2006. ASD/LRFD Manual for
Manual: Engineered Wood Construction, 2005 ed., AF&PA, Washington, DC.
IBC: International Codes Council (ICC). 2006. International Building Code (IBC), 2006 ed.,
ICC, Falls Church, VA.
NDS: American Forest and Paper Association (AF&PA). 2005. National Design Specification

ksi

kips per square inch (k/in.2)

mph

miles per hour

pcf

pounds per cubic foot (lb/ft3)

plf

pounds per lineal foot (lb/ft)

psf

pounds per square foot (lb/ft2)

psi

pounds per square inch (lb/in.2)

sec

second


xvi

Ecc.

eccentric

EMC

equilibrium moisture content

FBD

free-body diagram

FS

factor of safety

FSP

fiber saturation point

glulam

structural glued laminated timber

ht

height

IP


MC

moisture content based on oven-dry weight of wood

MDO

medium density overlay (plywood)

MEL

machine evaluated lumber

min.

minimum

MSR

machine stress rated lumber

NA

neutral axis

o.c.

on center

OM