Timber Designers' Manual

556 Pages·2006·3.44 MB·English

by  E. C. Ozelton

TIMBER
DESIGNERS’
MANUAL
Third Edition
Also of Interest
StructuralTimberDesigntoEurocode5
Jack Porteous & Adby Kermani
1 4051 4638 9
978 14051 4638 8
StructuralMasonryDesigners’Manual
Third Edition
W.G. Curtin, G. Shaw, J.K. Beck & W.A. Bray
Revised by David Easterbrook
0 6320 5612 6
978 06320 5612 5
StructuralFoundationDesigners’Manual
Second Edition
W.G. Curtin, G. Shaw, G.I. Parkinson & J.M. Golding
Revised by N.J. Seward
1 4051 3044 X
978 14051 3044 8
SteelDesigners’Manual
Sixth Edition
The Steel Construction Institute
1 4051 3412 7
978 14051 3412 5
TIMBER DESIGNERS’
MANUAL
E. C. Ozelton & J. A. Baird
Third Edition
revised by
E. C. Ozelton
Blackwell
Science
©J. A. Baird and E. C. Ozelton 1976, 1984 (First and Second editions)
©E. C. Ozelton 2002, 2006 (Third edition)
Blackwell Science Ltd, a Blackwell Publishing company
Editorial offices:
Blackwell Science Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK
Tel: [phone]
Blackwell Publishing Inc., 350 Main Street, Malden, MA02148-5020, USA
Tel: [phone]
Blackwell Science Asia Pty, 550 Swanston Street, Carlton, Victoria 3053, Australia
Tel: [phone]
The right of the Author to be identified as the Author of this Work has been asserted in accordance with the
Copyright, Designs and Patents Act 1988.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in
any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by
the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher.
First edition published in Great Britain by Crosby Lockwood Staples 1976
Reprinted by Granada Publishing Ltd 1981, 1982
Second edition published 1984
Reprinted by Collins Professional and Technical Books 1987
Reprinted with updates by BSPProfessional Books 1989
Reprinted 1990
Reprinted by Blackwell Science 1995
Third edition published 2002
Reprinted 2004
Reissued in paperback 2006
ISBN-10: 1-405-14671-0
ISBN-13: 978-1-405-14671-5
Library of Congress Cataloging-in-Publication Data is available
Acatalogue record for this title is available from the British Library
Set in 10 on 12 pt Times
by SNPBest-set Typesetter Ltd., Hong Kong
Printed and bound in Singapore
by Markono Print Media Pte Ltd
The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which
has been manufactured from pulp processed using acid-free and elementary chlorine-free practices. Furthermore,
the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation
standards.
For further information on Blackwell Publishing, visit our website:
www.blackwellpublishing.com
Contents
Preface xi
Acknowledgements xii
About the Authors xiii
1. The Materials Used in TimberEngineering 1
1.1 Introduction 1
1.2 Timber 2
1.3 Plywood 22
1.4 Particleboard, oriented strand board, cement-bonded particleboard and
wood fibreboards 26
1.5 Engineered wood products 31
1.6 Mechanical fasteners 34
1.7 Adhesives used in timber engineering 38
2. Stress Levels forSolid Timber 41
2.1 Introduction 41
2.2 Derivation of basic stress and characteristic strength values 42
2.3 Modulus of elasticity and shear modulus 45
2.4 Grade stress 46
2.5 Load sharing 48
2.6 Moisture content 48
3. Loading 50
3.1 Types of loading 50
3.2 Load duration 50
3.3 Concentrated loadings 51
3.4 Dead loading 52
3.5 Imposed loadings for floors 52
3.6 Imposed loadings for roofs 53
3.7 Snow loading 53
3.8 Roof loadings on small buildings 54
3.9 Wind loading 55
3.10 Unbalanced loading 59
3.11 Combinations of loading 60
3.12 Special loadings 60
4. The Design of Beams: General Notes 64
4.1 Related chapters 64
4.2 Design considerations 64
v
vi Contents
4.3 Effective design span 65
4.4 Load-sharing systems 65
4.5 Load–duration factor 68
4.6 Lateral stability 69
4.7 Moisture content 70
4.8 Bending stresses 71
4.9 Depth and form factors 72
4.10 Bearing 73
4.11 Shear 75
4.12 The effect of notches and holes 77
4.13 Shear in beams supported by fastenings and in eccentric joints 80
4.14 Glue-line stresses 83
4.15 Deflection 86
4.16 Bending and shear deflection coefficients 95
5. Beams of Solid Timber 99
5.1 Introduction 99
5.2 General design 99
5.3 Principal beams of solid timber 100
5.4 Load-sharing systems of solid timber 103
5.5 Geometrical properties of solid timber sections in service
classes 1 and 2 106
5.6 Principal members bending about both the x–x and y–y axes 106
6. Multiple Section Beams 117
6.1 Introduction 117
6.2 Modification factors 117
6.3 Connection of members 117
6.4 Standard tables 122
6.5 Design example 122
7. Glulam Beams 123
7.1 Introduction 123
7.2 Timber stress grades for glulam 126
7.3 Strength values for horizontally or vertically laminated beams 127
7.4 Appearance grades for glulam members 130
7.5 Joints in laminations 132
7.6 Choice of glue for glulam 136
7.7 Preservative treatment 136
7.8 Standard sizes 137
7.9 Tables of properties and capacities of standard size in C24 grade 137
7.10 Typical designs 150
7.11 The calculation of deflection and bending stress of glulam beams with
tapered profiles 152
8. Thin Web Beams 164
8.1 Introduction 164
8.2 Primary design considerations 164
Contents vii
8.3 Design examples 172
8.4 Web splices 177
8.5 Web stiffeners 178
8.6 Holes or slots in ply web beams 180
8.7 Proprietary sections 181
9. Lateral Stability of Beams 190
9.1 Introduction 190
9.2 Buckling of rectangular solid and glulam sections 190
9.3 Design examples 195
9.4 Partially restrained thin web I beams 199
10. Structural Composite Lumber 201
10.1 Introduction 201
10.2 Kerto-LVL(Laminated Veneer Lumber) 201
10.3 Versa-Lam SPLVL(Laminated Veneer Lumber) 202
10.4 Parallam PSL(Parallel Strand Lumber) 204
10.5 TimberStrand (Laminated Strand Lumber) 206
11. Solid TimberDecking 211
11.1 Introduction 211
11.2 Span and end joint arrangements 211
11.3 Nailing of decking 214
11.4 Design procedure 217
11.5 Species of decking, grades and capacities 218
11.6 Example of design of decking 218
12. Deflection. Practical and Special Considerations 221
12.1 Deflection limits 221
12.2 Camber 222
12.3 Deflection due to dead load only on uncambered beams 223
12.4 Deflection due to wind uplift on roofs or wind on walls 223
12.5 Deflection stages due to sequence of erection 224
12.6 Examples of cases which require special consideration in
deflection/camber calculations 224
12.7 Effect of deflection on end rotation of beams 234
13. Tension Members 236
13.1 Axial tensile loading 236
13.2 Width factor 236
13.3 Effective cross section 236
13.4 Combined bending and tensile loading 237
13.5 Tension capacities of solid timber sections containing split ring
or shear plate connectors 240
14. General Design of Compression Members 242
14.1 Related chapters 242
14.2 Design considerations 242
viii Contents
14.3 Effective length 242
14.4 Permissible compressive stress 245
14.5 Maximum slenderness ratio 246
14.6 Combined bending and axial loading 246
14.7 Effective area for compression 248
14.8 Deflection and sway of columns 249
14.9 Bearing at bases 249
14.10 Bearing at an angle to grain 251
15. Columns of Solid Timber 252
15.1 Introduction 252
15.2 Design example 252
15.3 Deflection of compression members 259
16. Multi-memberColumns 261
16.1 Introduction 261
16.2 Combined bending and axial loading for tee sections 261
16.3 Tee section: design example 262
16.4 Spaced columns 265
16.5 Example of spaced column design 267
16.6 Compression members in triangulated frameworks 269
17. Glulam Columns 271
17.1 Introduction 271
17.2 Timber stress grades for glulam columns 271
17.3 Joints in laminations 273
17.4 Example of combined bending and compression in a glulam
section 273
17.5 Check on strength of a finger joint in combined bending and
compression 278
18. Mechanical Joints 280
18.1 General 280
18.2 Nailed joints 284
18.3 Screw joints 290
18.4 Bolted joints 295
18.5 Toothed plate connector units 307
18.6 Split ring and shear plate connectors 324
19. Glue Joints, including FingerJoints 336
19.1 Introduction 336
19.2 Types of adhesive used in timber engineering 337
19.3 Quality control requirements. General glue joints 337
19.4 The strength of a glue joint 341
19.5 Structural finger joints 342
19.6 Quality control requirements for structural finger joints 344
19.7 The strength and design of finger joints 346
Contents ix
20. Stress Skin Panels 352
20.1 Introduction 352
20.2 Forms of construction 352
20.3 Special design considerations 353
20.4 Selecting a trial design cross section 356
20.5 Permissible stresses 356
20.6 Self-weight of panel elements 357
20.7 Typical design for double-skin panel 357
20.8 Splice plates 363
20.9 Typical design for single-skin panel 365
21. Trusses 369
21.1 Introduction 369
21.2 Loading on trusses 375
21.3 Types of members and joints 376
21.4 Design of a parallel-chord truss 386
21.5 Bowstring trusses 399
21.6 Deflection of trusses 408
21.7 Coefficients of axial loading 411
22. Structural Design forFire Resistance 430
22.1 Introduction 430
22.2 Properties of timber in fire 431
22.3 Design method for the residual section 433
22.4 Stress grade 433
22.5 Ply web beams 434
22.6 Connections 434
22.7 Testing for fire resistance 434
22.8 Proprietary treatments for surface spread of flame 434
22.9 Check on the fire resistance of a glulam beam 434
22.10 Check on the fire resistance of a glulam column 435
23. Considerations of Overall Stability 438
23.1 General discussion 438
23.2 No sway condition 438
23.3 With sway condition 440
23.4 Diaphragm action 443
23.5 Horizontal diaphragms 443
23.6 Vertical shear walls 449
24. Preservation, Durability, Moisture Content 454
24.1 Introduction: preservation 454
24.2 Durability 454
24.3 Amenability to preservative treatment 456
24.4 Risk and avoidance 457
24.5 Types of preservative 458
24.6 Additional notes on preservation 460