Design of Wood Structures (BBS) - E. Breyer, J. Fridley, E. Cobeen, G. Pollock, Notas de estudo de Design

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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

iii

Contents

Preface ix Nomenclature xiii

Chapter

6.16 Design Problem: Glulam with Compression Zone Stressed in

Chapter

15.4 Connection Details—Diaphragm to Concrete or Masonry

• Chapter 1. Wood Buildings and Design Criteria 1. Abbreviations xvi
  • 1.1 Introduction 1.
  • 1.2 Types of Buildings 1.
  • 1.3 Required and Recommended References 1.
  • 1.4 Building Codes and Design Criteria 1.
  • 1.5 ASD and LRFD 1.
  • 1.6 Organization of the Text 1.
  • 1.7 Structural Calculations 1.
  • 1.8 Detailing Conventions 1.
  • 1.9 Fire-Resistive Requirements 1.
  • 1.10 Industry Organizations 1.
  • 1.11 References 1.
• Chapter 2. Design Loads 2.
  • 2.1 Introduction 2.
  • 2.2 Dead Loads 2.
  • 2.3 Live Loads 2.
  • 2.4 Snow Loads 2.
  • 2.5 Soil Loads and Hydrostatic Pressure 2.
  • 2.6 Loads due to Fluids 2.
  • 2.7 Rain Loads 2.
  • 2.8 Flood Loads 2.
  • 2.9 Self-straining Loads 2.
  • 2.10 Wind Loads—Introduction 2.
  • 2.11 Wind Forces—Main Wind Force Resisting System 2.
  • 2.12 Wind Forces—Components and Cladding 2.
  • 2.13 Seismic Forces—Introduction 2.
• 2.14 Seismic Forces 2.
• 2.15 Seismic Forces—Primary System 2.
  • 2.16 Seismic Forces—Wall Components 2. iv
  • 2.17 Load Combinations 2.
  • 2.18 Serviceability/Deflection Criteria 2.
  • 2.19 References 2.
  • 2.20 Problems 2.
• Chapter 3. Behavior of Structures under Loads and Forces 3.
  • 3.1 Introduction 3.
  • 3.2 Structures Subject to Vertical Loads 3.
  • 3.3 Structures Subject to Lateral Forces 3.
  • 3.4 Lateral Forces in Buildings with Diaphragms and Shearwalls 3.
  • 3.5 Design Problem: Lateral Forces on One-Story Building 3.
  • 3.6 Design Problem: Lateral Forces on Two-Story Building 3.
  • 3.7 References 3.
  • 3.8 Problems 3.
• Chapter 4. Properties of Wood and Lumber Grades 4.
  • 4.1 Introduction 4.
  • 4.2 Design Specification 4.
  • 4.3 Methods of Grading Structural Lumber 4.
  • 4.4 In-Grade Versus Clear Wood Design Values 4.
  • 4.5 Species and Species Groups 4.
  • 4.6 Cellular Makeup 4.
  • 4.7 Moisture Content and Shrinkage 4.
  • 4.8 Effect of Moisture Content on Lumber Sizes 4.
  • 4.9 Durability of Wood and the Need for Pressure Treatment 4.
  • 4.10 Growth Characteristics of Wood 4.
  • 4.11 Sizes of Structural Lumber 4.
  • 4.12 Size Categories and Commercial Grades 4.
  • 4.13 General Notation 4.
  • 4.14 Wet Service Factor CM 4.
  • 4.15 Load Duration Factor C D (ASD Only) 4.
  • 4.16 Time Effect Factor  (LRFD Only) 4.
  • 4.17 Size Factor CF 4.
  • 4.18 Repetitive Member Factor Cr 4.
  • 4.19 Flat Use Factor Cfu 4.
  • 4.20 Temperature Factor Ct 4.
  • 4.21 Incising Factor Ci 4.
  • 4.22 Resistance Factor (LRFD Only) 4.
  • 4.23 Format Conversion Factor KF (LRFD Only) 4.
  • 4.24 Design Problem: Adjusted Design Values 4.
  • 4.25 Future Directions in Wood Design 4.
  • 4.26 References 4.
  • 4.27 Problems 4.
• Chapter 5. Structural Glued Laminated Timber 5.
  • 5.1 Introduction 5.
  • 5.2 Sizes of Glulam Members 5.
  • 5.3 Resawn Glulam 5. v
  • 5.4 Fabrication of Glulams 5.
  • 5.5 Grades of Glulam Members 5.
  • 5.6 Adjustment Factors for Glulam 5.
  • 5.7 Design Problem: Adjusted Design Values 5.
  • 5.8 References 5.
  • 5.9 Problems 5.
• Beam Design 6. 6.
  • 6.1 Introduction 6.
  • 6.2 Bending 6.
  • 6.3 Lateral Stability 6.
  • 6.4 Adjusted Bending Design Value Summary 6.
  • 6.5 Shear 6.
  • 6.6 Deflection 6.
  • 6.7 Design Summary 6.
  • 6.8 Bearing at Supports 6.
  • 6.9 Design Problem: Sawn Beam 6.
  • 6.10 Design Problem: Rough-Sawn Beam Using ASD 6.
  • 6.11 Design Problem: Notched Beam 6.
  • 6.12 Design Problem: Sawn-Beam Analysis 6.
  • 6.13 Design Problem: Glulam Beam with Full Lateral Support 6.
  • 6.14 Design Problem: Glulam Beam with Lateral Support at 8 ft-0 in. 6.
  • 6.15 Design Problem: Glulam Beam with Lateral Support at 48 ft-
    • 6. in.
    • 6. Tension
  • 6.17 Cantilever Beam Systems 6.
  • 6.18 Lumber Roof and Floor Decking 6.
  • 6.19 Fabricated Wood Components 6.
  • 6.20 References 6.
  • 6.21 Problems 6.
• Axial Forces and Combined Bending and Axial Forces 7. 7.
  • 7.1 Introduction 7.
• 7.2 Axial Tension Members 7.
• 7.3 Design Problem: Tension Member 7.
• 7.4 Columns 7.
• 7.5 Detailed Analysis of Slenderness Ratio 7.
• 7.6 Design Problem: Axially Loaded Column 7.
• 7.7 Design Problem: Capacity of a Glulam Column 7.
• 7.8 Design Problem: Capacity of a Bearing Wall 7.
• 7.9 Built-Up Columns 7.
• 7.10 Combined Bending and Tension 7.
• 7.11 Design Problem: Combined Bending and Tension 7.
• 7.12 Combined Bending and Compression 7.
• 7.13 Design Problem: Beam-Column 7.
  • 7. LRFD
• 7.15 Design Problem: Glulam Beam-Column Using ASD 7.
• 7.16 Design for Minimum Eccentricity 7.
  • 7.17 Design Problem: Column with Eccentric Load Using ASD 7. vi
  • 7.18 References 7.
  • 7.19 Problems 7.
• Chapter 8. Wood Structural Panels 8.
  • 8.1 Introduction 8.
  • 8.2 Panel Dimensions and Installation Recommendations 8.
  • 8.3 Plywood Makeup 8.
  • 8.4 Species Groups for Plywood 8.
  • 8.5 Veneer Grades 8.
  • 8.6 Exposure Durability Classifications 8.
  • 8.7 Plywood Grades 8.
  • 8.8 Other Wood Structural Panels 8.
  • 8.9 Roof Sheathing 8.
  • 8.10 Design Problem: Roof Sheathing 8.
  • 8.11 Floor Sheathing 8.
  • 8.12 Design Problem: Floor Sheathing 8.
  • 8.13 Wall Sheathing and Siding 8.
  • 8.14 Stress Calculations for Wood Structural Panels 8.
  • 8.15 References 8.
  • 8.16 Problems 8.
• Chapter 9. Diaphragms 9.
  • 9.1 Introduction 9.
  • 9.2 Basic Diaphragm Action 9.
  • 9.3 Shear Resistance 9.
  • 9.4 Diaphragm Chords 9.
  • 9.5 Design Problem: Roof Diaphragm 9.
  • 9.6 Distribution of Lateral Forces in a Shearwall 9.
  • 9.7 Collector (Strut) Forces 9.
  • 9.8 Diaphragm Deflections 9.
  • 9.9 Diaphragms with Interior Shearwalls 9.
  • 9.10 Interior Shearwalls with Collectors 9.
  • 9.11 Diaphragm Flexibility 9.
  • 9.12 References 9.
  • 9.13 Problems 9.
• Chapter 10. Shearwalls 10.
  • 10.1 Introduction 10.
  • 10.2 Basic Shearwall Action 10.
  • 10.3 Shearwalls Using Wood Structural Panels 10.
  • 10.4 Other Sheathing Materials 10.
  • 10.5 Shearwall Chord Members 10.
  • 10.6 Design Problem: Shearwall 10.
  • 10.7 Alternate Shearwall Design Methods 10.
  • 10.8 Anchorage Considerations 10.
  • 10.9 Vertical (Gravity) Loads 10.
  • 10.10 Lateral Forces Parallel to a Wall 10.
  • 10.11 Shearwall Deflection 10. vii
  • 10.12 Lateral Forces Perpendicular to a Wall 10.
  • 10.13 References 10.
  • 10.14 Problems 10.
• Chapter 11. Wood Connections—Background 11.
  • 11.1 Introduction 11.
  • 11.2 Types of Fasteners and Connections 11.
  • 11.3 Yield Model for Laterally Loaded Fasteners 11.
  • 11.4 Factors Affecting Strength in Yield Model 11.
  • 11.5 Dowel Bearing Strength 11.
  • 11.6 Plastic Hinge in Fastener 11.
  • 11.7 Yield Limit Mechanisms 11.
  • 11.8 References 11.
  • 11.9 Problems 11.
• Chapter 12. Nailed and Stapled Connections 12.
  • 12.1 Introduction 12.
  • 12.2 Types of Nails 12.
  • 12.3 Power-Driven Nails and Staples 12.
  • 12.4 Yield Limit Equations for Nails 12.
  • 12.5 Applications of Yield Limit Equations 12.
  • 12.6 Adjustment Factors for Laterally Loaded Nails 12.
  • 12.7 Design Problem: Nail Connection for Knee Brace 12.
  • 12.8 Design Problem: Top Plate Splice 12.
  • 12.9 Design Problem: Shearwall Chord Tie 12.
  • 12.10 Design Problem: Laterally Loaded Toenail 12.
  • 12.11 Design Problem: Laterally Loaded Connection in End Grain 12.
  • 12.12 Nail Withdrawal Connections 12.
  • 12.13 Combined Lateral and Withdrawal Loads 12.
  • 12.14 Spacing Requirements 12.
  • 12.15 Nailing Schedule 12.
  • 12.16 References 12.
  • 12.17 Problems 12.
• Chapter 13. Bolts, Lag Bolts, and Other Connectors 13.
  • 13.1 Introduction 13.
• 13.2 Bolt Connections 13.
• 13.3 Bolt Yield Limit Equations for Single Shear 13.
• 13.4 Bolt Yield Limit Equations for Double Shear 13.
• 13.5 Adjustment Factors for Bolts 13.
• 13.6 Tension and Shear Stresses at a Multiple Fastener Connection 13.
• 13.7 Design Problem: Multiple-Bolt Tension Connection 13.
• 13.8 Design Problem: Bolted Chord Splice for Diaphragm 13.
• 13.9 Shear Stresses in a Beam at a Connection 13.
• 13.10 Design Problem: Bolt Connection for Diagonal Brace 13.
• 13.11 Lag Bolt Connections 13.
• 13.12 Yield Limit Equations for Lag Bolts 13.
  • 13.13 Adjustment Factors for Lag Bolts in Shear Connections 13. viii
  • 13.14 Design Problem: Collector (Strut) Splice with Lag Bolts 13.
  • 13.15 Lag Bolts in Withdrawal 13.
  • 13.16 Combined Lateral and Withdrawal Loads 13.
  • 13.17 Split Ring and Shear Plate Connectors 13.
  • 13.18 References 13.
  • 13.19 Problems 13.
• Chapter 14. Connection Details and Hardware 14.
  • 14.1 Introduction 14.
  • 14.2 Connection Details 14.
  • 14.3 Design Problem: Beam-to-Column Connection 14.
  • 14.4 Cantilever Beam Hinge Connection 14.
  • 14.5 Prefabricated Connection Hardware 14.
  • 14.6 References 14.
• Chapter 15. Diaphragm-to-Shearwall Anchorage 15.
  • 15.1 Introduction 15.
  • 15.2 Anchorage Summary 15.
  • 15.3 Connection Details—Diaphragm to Wood-Frame Wall 15.
    • 15. Walls
  • 15.5 Subdiaphragm Anchorage of Concrete and Masonry Walls 15.
  • 15.6 Design Problem: Subdiaphragm 15.
  • 15.7 References 15.
• Chapter 16. Advanced Topics in Lateral Force Design 16.
  • 16.1 Introduction 16.
  • 16.2 Seismic Forces—Regular Structures 16.
  • 16.3 Seismic Forces—Irregular Structures 16.
  • 16.4 Overturning—Background 16.
  • 16.5 Overturning—Review 16.
  • 16.6 Overturning—Wind 16.
  • 16.7 Overturning—Seismic 16.
  • 16.8 Lateral Analysis of Nonrectangular Buildings 16.
  • 16.9 Rigid Diaphragm Analysis 16.
  • 16.10 Additional Topics in Diaphragm Design 16.

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 publications of the American Forest and Paper Association (AF&PA), the International Codes Council (ICC), the American Society of Civil Engineers (ASCE), APA—The Engineered Wood Association, and the American Institute of Timber Construction (AITC). In the writing of this text, an effort has been made to conform to the spirit and intent of the reference documents. The interpretations are those of the authors and are intended to reflect current structural design practice. The material presented is suggested as a guide only, and final design responsibility, lies with the structural engineer.

x The sixth edition of this book was promoted by five major developments:

1. Publication of new dual-format (ASD/LRFD) wood design criteria in the 2005 National Design Specification for Wood Construction ( NDS ).
2. Publication of the new Special Design Provisions for Wind and Seismic (SDPWS) Supplement to the NDS.
3. Publication of the comprehensive ASD/LRFD Manual for Engineered Wood Construction.
4. Publication and increased adoption nationally of the 2006 International Building Code.
5. Publication of updated load standards in the 2005 edition of Minimum Design Loads for Buildings and Other Structures (ASCE 7-05). The National Design Specification (NDS) is published by the American Forest & Paper Association (AF&PA) and represents the latest structural design recommendations by the wood industry. The 2005 NDS presents both traditional allowable stress design (ASD) provisions as well as new load and resistance factor design (LRFD) provisions. The inclusion of the LRFD provisions is new to the NDS for the 2005 edition. As such, the 2005 NDS is considered a dualformat design specification. While ASD has been and may continue to be the method of choice for many designers of wood buildings, the acceptance and use of LRFD for wood design is increasing. The 2006 ASD/LRFD Manual for Engineered Wood Construction includes design supplements, guidelines, and manuals helpful for wood engineering design. It includes design information for sawn lumber, structural glued laminated timber, structural-use panels, shearwalls and diaphragms, poles and piles, I-joists, structural 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.

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- www.alsc.org APA APA—The Engineered Wood Association P.O. Box 11700 Tacoma, WA 98411- www.apawood.org ASCE American Society of Civil Engineers 1801 Alexander Bell Drive Reston, VA 20191 www.asce.org ATC Applied Technology Council 201 Redwood Shores Parkway, Suite 240 Redwood City, CA 94065 www.atcouncil.org AWPA American Wood-Preservers’ Association P.O. Box 388 Selma, AL 36702- www.awpa.com BSSC Building Seismic Safety Council National Institute of Building Sciences 1090 Vermont Avenue, N.W., Suite 700 Washington, DC 20005 http://www.bssconline.org/ CANPLY Canadian Plywood Association 735 West 15 Street

North Vancouver, British Columbia, Canada V7M 1T www.canply.org CWC Canadian Wood Council 99 Bank Street, Suite 400 Ottawa, Ontario, Canada K1P 6B www.cwc.ca CPA–CWC Composite Panel Association Composite Wood Council 18922 Premiere Court Gaithersburg, MD 20879- 301-670- www.pbmdf.com