timber design and construction handbook pdf

No part of this work may be reproduced or copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher, unless otherwise permitted under the Copyright Act 1968. It represents the authors individual interpretation of AS 1720.12010, Timber structures, Part 1: Design methods, and should not be interpreted to necessarily reflect the opinion of the joint Standards Australia/Standards New Zealand Committee TM-001, Timber Structures. This Handbook can be used to develop the understanding and confidence necessary to efficiently and effectively design in timber. Throughout history, people have used wood for many reasons and enjoyed its beauty, workability and practicality. These products can be used in both well-established construction forms and innovative building systems as part of simple, large or iconic buildings and structures. Floor joists 50 mm wide by 200 mm high, simply supported, Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) SA HB 1082013 Timber design handbook HB SA HB 1082013 TIMBER DESIGN HANDBOOK Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) In accordance with the Australian Limit State Timber Design Standard AS 1720.12010 Timber structures, Part 1: Design methods Adjunct Associate Professor Geoffrey N. Boughton School of Engineering, James Cook University Director, TimberED Services Pty Ltd BE (hons), MEngSci (UWA), PhD (JCU), FIE (Aust), CPEng Professor Keith I. We are especially grateful for the continued support and encouragement of our families, during the development of the Handbook. Geoff Boughton Keith Crews February, 2013 SA HB 1082013 Timber Design Handbook iii CONTENTS 1.0 INTRODUCTION TO TIMBER DESIGN .. 1 1.1 INTRODUCTION 1 1.1.1 Structure of this Handbook. 1 1.1.2 Conventions used in this Handbook .. 2 1.1.3 Trees .. 3 1.2 BASIC WOOD PROPERTIES .. 5 1.2.1 Growth characteristics of wood 5 1.2.2 Structure of wood 7 1.2.3 Wood fibre sampling and properties . 8 1.3 STRUCTURAL TIMBER 11 1.3.1 Uses of structural timber 11 Domestic construction .11 Larger structures .13 1.3.2 Effects of processing timber 15 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) Residual stresses in timber 15 Drying and shrinkage17 Strength properties of sawn wood .18 1.3.3 Seasoning of timber and shrinkage.. 20 Measurement of moisture content .20 Seasoning degrade .20 Air-drying ..21 Kiln-drying 21 Other methods of seasoning .22 Shrinkage 22 1.3.4 Timber sorting or grading. 22 Visual stress grading.23 Machine stress-grading24 Machine proof-grading 25 1.3.5 In-grade testing .. 26 MGP, A-Grades and other products supported by in-grade data26 1.3.6 Grade designations .. 26 Characteristic strengths from small clear specimen tests ..28 Characteristic strengths from in-grade test data .28 The F-grade system ..29 Significance of an F-grade classification29 MGP grades ..29 GL grades ..30 Other grades..30 1.4 SELECTION OF SPECIES.. 31 1.4.1 Durability.. 32 Exposure to hazard 34 Natural durability35 1.4.2 Improvement of durability 36 Structural detailing 36 Chemical treatment39 Maintenance..43 1.4.3 Fire 44 Fire resistance levels (FRL)..45 Design for fire..45 1.4.4 Availability of Structural Timber . 46 Seasoning46 Standard sizes and grades ..47 Species .48 1.4.5 Workability.. 48 SA HB 1082013 iv Timber Design Handbook 1.4.6 Specifying and Ordering Timber.. 48 Size 48 Length ..49 Seasoning49 1.5 ENGINEERED TIMBER PRODUCTS . 50 1.5.1 Plywood . 50 1.5.2 Glued laminated timber (Glulam). 51 1.5.3 Laminated veneer lumber (LVL).. 52 1.5.4 Strand and flake products . 53 Particleboard .53 Oriented strand board (OSB) 53 Strand lumber (LSL and ESL).53 1.5.5 Cross laminated timber (CLT) 53 1.6 PRACTICE PROBLEMS. 55 1.7 REFERENCES CHAPTER 1 . 56 2.0 LIMIT STATES DESIGN 59 2.1 DESIGN PROCESS.. 60 2.1.1 Criteria 60 2.1.2 Design constraints. 60 Legislative constraints .61 Other constraints.61 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) 2.1.3 Steps in the design process .. 62 Problem definition .63 Information search .63 Structural system (conceptual design) .63 Preliminary design of the structure67 Detailed design of members and connections .67 Drawings and specifications .67 Advice during construction ..69 2.1.4 Design calculations.. 69 Requirements 69 Layout ..69 2.1.5 Structural analysis. 70 Tributary areas for evaluating loads .72 Example 2.1 Contributing area for floor member design .76 2.2 LOADS ON STRUCTURAL ELEMENTS 79 2.2.1 Classification of loads 79 Origin of loads .79 Distribution of the load80 Certainty of the load .81 Duration of the load ..81 Design forces and moments..82 Conservatism 82 2.2.2 Permanent actions. 82 Design summaryPermanent actions.84 Example 2.2 Permanent actions on internal bearer .84 2.2.3 Imposed actions . 85 Distribution of imposed actions..87 Certainty of imposed actions 87 Duration of imposed actions.87 Roof imposed loads ..89 Floor imposed loads..91 Known floor imposed actions..91 Estimated floor imposed actions.91 Concentrated floor imposed loads .93 Imposed load reductions with area 93 Design summaryImposed loads.94 Example 2.3 Imposed actions on internal bearer94 SA HB 1082013 Timber Design Handbook v 2.2.4 Wind actions 96 Wind velocity ..98 Velocity modification factors ..99 Wind pressure 103 External wind pressure .104 Internal wind pressure ..108 Net force on a structural element.109 Design summaryWind loads.109 Example 2.4 Wind loads on building elements ..110 2.2.5 Snow actions. 117 Ground snow loads in alpine regions 118 Ground snow loads in sub-alpine regions119 Building snow loads in alpine regions..119 Building snow loads in sub-alpine regions.120 Design summarySnow actions.120 Example 2.5 Snow loads on a roof 121 2.2.6 Earthquake actions. 123 Structure classification .124 Design method ..125 Site Hazard .125 Site sub-soil class.126 Earthquake load evaluation 127 Common elements of earthquake design.128 Earthquake Design Category I..128 Earthquake Design Category II 129 Earthquake Design Category III Dynamic analysis132 Design summaryEarthquake actions 132 Example 2.6 Earthquake loads on a building ..133 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) 2.2.7 Other loads. 135 Liquid pressure .136 Earth pressure 137 Loads due to settlement 137 Loads due to temperature 138 Impact loads139 2.2.8 Summary of Loadings . 139 2.3 LIMIT STATES .. 141 2.3.1 Serviceability limit state . 141 Serviceability limits 141 Serviceability modelling..142 Serviceability load combinations.144 Design for serviceability..145 Example 2.7 Guess and check for beam serviceability ..146 Example 2.8 Smart design method for beam serviceability .147 2.3.2 Stability limit state. 148 Stability load combinations 148 Design for stability .149 Example 2.9 Truss anchorage..149 2.3.3 Strength limit state. 150 Strength limit state loads .150 Strength of structural elements .152 Design for strength .152 Strength load combinations 154 Example 2.10 Strength limit state load combinations .156 2.3.4 Capacity factor () . 157 Category of timber member or connection.158 Role of the element in the structure159 Selection of factor162 Example 2.11 Capacity factor .163 2.4 PRACTICE PROBLEMS.. 164 2.4.1 Short answer problems 164 2.4.2 Calculation problems 165 2.5 REFERENCES CHAPTER 2 .. 170 SA HB 1082013 vi Timber Design Handbook 3.0 DESIGN OF TENSION MEMBERS.. 173 3.1 STRENGTH LIMIT STATE . 174 3.1.1 Characteristic tensile strength (f 't ) . 176 Example 3.1 Design characteristic tensile strength ..177 3.1.2 Duration of load and k1 factor.. 177 Duration of load (strength limit state) ..178 Imposed actions in combinations 179 Example 3.2 Duration of load factor 181 Identification of the critical load combination .182 3.1.3 Partial seasoning and k4 factor. 182 Partial seasoning in service.182 Equilibrium moisture content 183 Partial seasoning factor k4..184 Seasoned timber used in moist environments184 Unseasoned timber in dry environments .185 Common practice among designers185 Identification of the critical load combination .185 3.1.4 Ambient temperature and k6 factor 186 3.1.5 Capacity of tension members .. 187 Flow chart for the design capacity of tension members ..187 Example 3.3 Tensile capacity ..188 3.1.6 Plywood tension elements . 189 Modification factor for moisture condition (k19) .190 Assembly factor (g19) and effective area (At) 190 3.2 SERVICEABILITY LIMIT STATE. 192 3.2.1 Creep and j3 factor 192 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) Duration of load for serviceability..193 3.2.2 Checking serviceability performance .. 194 3.3 DESIGN OF TENSION MEMBERS .. 195 3.3.1 Design techniques for tension members. 195 Design summaryTension members ..196 Example 3.4 Tension member design - seasoned timber ..196 Example 3.5 Tension member design - unseasoned timber .200 3.4 PRACTICE PROBLEMS.. 205 3.4.1 Short answer problems 205 3.4.2 Calculation problems 205 3.5 REFERENCES CHAPTER 3 .. 208 4.0 DESIGN OF COMPRESSION MEMBERS .. 209 4.1 BUCKLING IN COMPRESSION MEMBERS .. 210 4.1.1 Effective length 212 4.1.2 Compression capacity.. 214 4.2 STRENGTH 215 4.2.1 Characteristic compression strength (f 'c) .. 218 4.2.2 Buckling and k12 factor .. 218 Material constant for compression members (c )..220 Slenderness of compression members (S) .222 Effective length.225 k12 for slender compression members..230 k12 for stocky compression members230 k12 for compression members at the transition from stocky to slender231 4.2.3 Capacity of compression members 231 Capacity of nail-laminated compression members.232 Flow chart for the design capacity of compression members233 Example 4.1 Compression capacity..234 SA HB 1082013 Timber Design Handbook vii 4.2.4 Columns with multiple compression elements 236 x axis buckling of composite member ..237 y axis buckling of composite member ..238 Buckling of individual shafts about their own minor axes between packing pieces .239 Limiting capacity of spaced columns carrying axial compression.239 Example 4.2 Capacity of spaced columns .239 4.2.5 Plywood compression elements.. 242 Stability factor for plywood (k12).243 Modification factor for moisture condition (k19) .244 Assembly factor (g19) and effective area (Ac) 244 4.3 SERVICEABILITY LIMIT STATE. 246 4.3.1 Creep and j2 factor 247 Duration of load for serviceability..247 4.3.2 Checking serviceability performance .. 248 4.4 DESIGN OF COMPRESSION MEMBERS 249 4.4.1 Design techniques for compression members . 249 Design assistance for compression members 251 Design summaryCompression members 252 Example 4.3 Design of a load bearing stud column .255 Example 4.4 Modification of design of wall studs from example 4.2.259 4.5 PRACTICE PROBLEMS.. 262 4.5.1 Short answer problems 262 4.5.2 Calculation problems 262 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) 4.6 REFERENCES CHAPTER 4 .. 266 5.0 DESIGN OF BENDING MEMBERS . 267 Design span.268 5.1 SERVICEABILITY LIMIT STATE. 270 5.1.1 Vibrations .. 270 Excitation.270 Dynamic structural response .271 Acceptability criteria .271 Design to avoid vibration 272 5.1.2 Deflections 272 Deflection limits ..273 Modulus of elasticity .276 Design dimensions..277 Camber..277 5.1.3 Creep under long-term loading 279 Moisture content and creep.279 Recoverable creep281 Irrecoverable creep .282 5.1.4 Duration of load and the j2 factor .. 282 Initial moisture content .282 Duration of load283 Duration of load factor for serviceability, ( j2 ) 284 5.1.5 Deflection calculations 285 5.1.6 Design for the serviceability limit state.. 286 5.2 STRENGTH LIMIT STATE IN FLEXURE 287 5.2.1 Characteristic bending strength (f 'b) 289 Reduction in strength of larger bending members..289 5.2.2 Strength sharing factor (k9) 290 Combined strength sharing systems ..292 Discrete strength sharing systems293 Strength sharing factor k9 ..294 Strength sharing factor for glulam and LVL .295 SA HB 1082013 viii Timber Design Handbook 5.2.3 Lateral-torsional buckling and the k12 factor 296 Stability factor for lateral torsional buckling.297 Material constant for beams ( b).299 Critical edge300 Restraint of bending members ..300 Effective continuous lateral restraint (CLR) .302 Beam slenderness (S1 or S2)..303 Stability factor for beams (k12) 307 Stability of LVL and glulam beams ..308 Stability of cantilever beams .308 5.2.4 Capacity of bending members . 308 Flow chart for the design capacity of bending members.308 Example 5.1 Design capacity of a formwork bearer 309 5.2.5 Design for flexure at the strength limit state 311 5.3 STRENGTH LIMIT STATE FOR SHEAR . 317 5.3.1 Shear capacity.. 320 5.3.2 Characteristic shear strength (f 's) . 321 Size effects..321 5.3.3 Shear area (As) . 322 5.3.4 Shear capacity.. 322 Flow chart for the design shear capacity of bending members 323 Design for shear capacity 323 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) 5.4 STRENGTH LIMIT STATE FOR BEARING 324 5.4.1 Bearing capacity . 325 5.4.2 Characteristic bearing strength 326 Bearing perpendicular to grain .327 Bearing parallel to grain ..327 5.4.3 Bearing length and k7 factor .. 328 5.4.4 Bearing capacity at an angle to the grain 329 5.4.5 Calculation of bearing capacity .. 330 Flow chart for calculation of bearing capacity normal to grain331 Flow chart for calculating bearing capacity at an angle to the grain. What do you see as its future? The work of many people over almost a century in Australia has led to the understanding that has been captured in this book so that future generations of timber engineers can benefit from their work. Many helpful comments and corrections have come from students and other academics during this time. The comprehensive index and table of contents will also help readers use the Handbook as a reference tool to find answers to specific questions. The appendices include a comprehensive list of cross-sectional properties for commonly used structural timber products and guidance on selecting design parameters. In particular, in conjunction with the first edition, we would like to thank: Colin MacKenzie (Technical Director of Timber Queensland), Mick McDowel and Leigh Punton (then of EWPAA) for their extensive review of the text. All rights reserved. Offer your visitors information that will make them interested in your business and the work that you do. Crazy Price websites ensures that we manage your project professionally from beginning until end as quick as possible. The second edition has been developed to reflect changes to AS 1720.1 and to the loading standards since the publication of the first edition. We make sure that every project we work on becomes noticed and seen. Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) 517 7.32 - Example 7.3 - system capacity of dowels.521 7.33 Concealed structural connections using epoxied steel dowels524 7.34 Shear transfer in epoxy injected dowels.525 7.35 Load transfer in connections 527 7.36 Tension perpendicular to grain at connections528 7.37 Detailing connections with tension perpendicular to grain..529 7.38 Prevention of transverse restraint in bolted connections530 7.39 Truss anchorage strap connections537 7.40 Column to beam connection.538 7.41 Connection between web members and lower chord in truss .539 7.42 Splice in tension member ..539 SA HB 1082013 xvi Timber Design Handbook Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) TABLES Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table Table 1.1 Historical stress grades for structural grades..24 1.2 Relative strength of structural grades .24 1.3 In-grade properties for MGP12 compared with those for F8 material ..30 1.4 Biological hazard classification.35 1.5 Natural durability classification of heartwood of some common Australian timbers in ground decay 35 1.6 General guide to probable life expectancy ..36 1.7 CCA treatment by hazard class and natural durability ..41 1.8 Guidance for scheduling of maintenance .43 1.9 Guidance for maintenance of exterior wood finishes.44 1.10 Availability - seasoned softwoods.47 1.11 Availability - unseasoned hardwoods..47 2.1 Spans for various structural systems (Source: Canadian Wood Council, 2005) ..65 2.2 Bending moments for different loading diagrams on prismatic beams.75 2.3 Unit weights of common building materials used in timber construction83 2.4 Common floor imposed actions.92 2.5 Earthquake hazard factors (Z) for major centres 126 2.6(a) Site sub-soil classes for earthquake actions 126 2.6(b) Spectral shape factors (Ch)..127 2.7 Selection of Earthquake Design Categories 127 2.8 Structural response factor ..131 2.9 Characteristics of structural loads .140 2.10 Estimating 5th percentiles of modulus of elasticity.143 2.11 Capacity factors for structural timber and connections 162 3.1 Character of loading in strength limit states combinations ..180 3.2 Estimated duration of load for different types of loading .181 3.3 Partial seasoning factor k4 for initially unseasoned timber.185 3.4 Assembly factor and effective area - plywood in tension .191 4.1 Effective length factor g13 228 4.2 Slenderness of columns ..229 4.3 Effective length factor g28 for spaced columns 238 4.4 Assembly factor and effective area plywood in compression .245 4.5 Design k12 for seasoned timber columns 253 4.6 Design k12 for unseasoned timber columns ..254 5.1 Ranges of common deflection limits for timber structural elements275 5.2 Duration of load for strength and serviceability limit states 284 5.3 Geometric parameters used in the evaluation of strength sharing factor k9 295 5.4 Maximum Lay to give k12 = 1.0 with lateral restraint on critical edge .312 5.5 Maximum La to give k12 = 1.0 with CLR on non-critical edge.313 5.6 Maximum Lay to give k12 = 1.0 with lateral restraints on critical edge314 5.7 Maximum La to give k12 = 1.0 with CLR on non-critical edge.314 5.8 Values of grain orientation factor ktg for 10. Galleries either give us a good or bad impression within the first few seconds of viewing. Dr Stephan Bernard (then of University of Western Sydney) and Prof. Andy Buchanan (University of Canterbury, NZ), gave valuable feedback from a teaching perspective, and the late Prof. Borg Madsen (Vancouver, Canada), provided inspiration and guidance even before the Handbook was started. It provides: explanations of timber behaviour; mathematical expressions that model the material behaviour; easy-to-use tables that complement those in the Standard; step-by-step design summaries; illustrations and worked examples using Australian Standards; and practice problems to reinforce the understanding of behaviour and enhance design skills. While every effort has been made to ensure the correctness of the contents, no responsibility for its use can be taken by Standards Australia or the Authors. That is why our focus is to give your business/brand an edge in the digital world. The timber engineering community in Australia has developed design and analysis methods that suit our collection of engineering products and service environments. 2 Originated as HB 1081998. Information is presented in a way that helps readers develop a feel for the behaviour of timber, and an understanding of both what to do and why it has to be done. Boris Iskra Forest & Wood Products Australia National Manager, Codes & Standards SA HB 1082013 ii Timber Design Handbook This Handbook is dedicated to Dr Robert (Bob) Leicester, formerly a Chief Research Scientist CSIRO, whose work over many years has underpinned much of the limit states Timber Design Standard, AS 1720.1. The bulk of your content creation and optimization should be centered on which problems you can solve for your customers and clients. 331 Design for bearing capacity 332 5.5 DEEP SECTION AND LONG SPAN CURVED OR TAPERED BEAMS 333 5.5.1 Design of straight constant depth glulam and LVL beams .. 333 Capacity of straight glulam and LVL beams.333 5.5.2 Behaviour of curved and/or tapered beams .. 334 Induced radial stresses ..334 Grain and stress orientation 334 5.5.3 Capacity of single-tapered straight beams. 335 Grain orientation factor (ktg) ..336 Taper angle factor (ktb) .337 Example 5.2 Single-tapered glulam beam .338 5.5.4 Capacity of double-tapered, curved and pitched cambered beams 340 Capacity limited by flexure 340 Shape factor (ksh) .342 Radius of curvature factor (kr) ..343 Capacity limited by radial tension ..344 Volume/size factor (kv) .345 Factor for radial stress effects (ktp) .346 Example 5.3 Pitched cambered glulam beam..347 5.6 DESIGN CAPACITY OF STRUCTURAL PLYWOOD IN BENDING . 349 5.6.1 Out-of-plane bending capacity (Md,p) .. 350 Modification factor for moisture condition (k19) .351 Assembly factor (g19) and effective section modulus (Zp) .351 Effective section modulus for out-of-plane bending spans parallel to face grain (Zp) .351 Assembly factor for bending spans parallel to face grain (g19) 352 Effective section modulus for out-of-plane bending spans perpendicular to face grain (Zp) 352 Assembly factor for bending spans perpendicular to face grain (g19) ..353 SA HB 1082013 Timber Design Handbook ix 5.6.2 In-plane bending capacity (Md,i) .. 353 Stability factor for plywood (k12).354 Modification factor for moisture condition (k19) .354 Assembly factor (g19) and effective in-plane section modulus (Zi) 355 Effective in-plane section modulus (Zi) 355 Assembly factor for in-plane bending (g19) ..355 5.6.3 Inter-lamina shear capacity (beam shear) (Vd,p).. 356 Modification factor for moisture condition (k19) .357 Assembly factor (g19) and effective shear area (As)357 Effective shear area for shear due to out-of-plane loads (As) 358 Assembly factor for shear due to out-of-plane loads (g19) .359 5.6.4 In-plane shear capacity (panel shear) (Vd,i) 359 Stability factor for plywood (k12).360 Modification factor for moisture condition (k19) .360 Assembly factor (g19) and effective shear area (As)360 Effective shear area for shear due to in-plane loads (As) .361 Assembly factor for in-plane shear (g19) .362 5.7 DESIGN TECHNIQUES FOR BEAMS.. 363 Load ratios ..363 5.7.1 Design for the serviceability limit state.. 364 Design summaryBending members selected for serviceability..364 Example 5.4 Serviceability design of a portal rafter 365 Example 5.5 Serviceability design of a floor support beam.373 5.7.2 Design for the strength limit state.. 375 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) Design summaryBending members selected for strength .376 Example 5.6 Design of a floor beam for strength..377 Example 5.7 Design of floor joists for strength..383 5.8 PRACTICE PROBLEMS.. 392 5.8.1 Short answer problems 392 5.8.2 Calculation problems 392 5.9 REFERENCES CHAPTER 5 .. 397 6.0 MEMBERS CARRYING COMBINED ACTION EFFECTS 399 Beam/columns ..400 6.1 SECOND ORDER EFFECTS 401 6.1.1 Structural analysis.. 402 First order analysis..402 Second order analysis 402 6.1.2 Estimate of moment amplification 403 Braced members ..403 Sway members..404 Example 6.1 Second order effects for beam/column.406 6.2 COMBINED BENDING AND COMPRESSION .. 409 6.2.1 Bending about the major axis (Md,x) with minor axis buckling (Nd,cy) . 409 6.2.2 Bending about the major axis (Md,x) with major axis buckling (Nd,cx) 411 6.2.3 Bending about the minor axis (Md,y) with axial compression (Nd,c) . 412 6.2.4 Checking beam/column capacity 413 Combined actions flow chartBending and compression 413 Compression capacities 414 Bending capacities ..414 Example 6.2 Combined actions on beam/column .414 6.3 COMBINED BENDING AND TENSION.. 419 6.3.1 Major axis bending (Md,x) with axial tension ( Nd,t) Tension edge . 419 6.3.2 Major axis bending (Md,x) with axial tension (Nd,t) Compression edge 420 6.3.3 Minor axis bending (Md,y) with axial tension (Nd,t) 423 6.3.4 Checking combined bending and tension members . 423 Tension capacity ..423 Bending capacities ..423 Combined actions flow chartBending and tension 424 Example 6.3 Combined actions on bending/tension member .424 SA HB 1082013 x Timber Design Handbook 6.4 BIAXIAL BENDING . 428 6.4.1 Biaxial bending and compression.. 428 6.4.2 Biaxial bending and tension . 428 6.5 PRACTICE PROBLEMS.. 430 6.5.1 Short answer problems 430 6.5.2 Calculation problems 430 6.6 REFERENCES CHAPTER 6 .. 434 7.0 DESIGN OF CONNECTIONS 435 7.1 CONNECTIONS 436 7.1.1 Elements in connections . 436 Connector.436 Connection..436 Type 1 connection ..436 Type 2 connection ..436 Common types of connections .437 Timber in connections ..439 7.1.2 Connectors . 440 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) Nails440 Nailplates .441 Screws441 Bolts442 Coach screws .443 Split-ring connectors..443 Shear-plate connectors..444 Metal dowels..445 7.1.3 Connection modelling.. 445 Geometry of connections.445 Shear planes 448 Positioning of fasteners 449 Fastener spacing ..449 Edge distance .451 End distance451 Strength modelling of connections .451 Serviceability modelling of connections .451 7.2 STRENGTH AND SERVICEABILITY OF NAILED CONNECTIONS 453 7.2.1 Type 1 nailed connections . 453 Capacity factor..454 7.2.2 7.2.3 7.2.4 7.2.5 Characteristic nail strength (Qk) 455 Duration of load factor (k1).. 456 Grain orientation factor (k13) .. 457 Shear plane factor (k14) .. 458 7.2.6 7.2.7 7.2.8 7.2.9 7.2.10 7.2.11 Head fixity factor (k16) 459 Factor for multiple nails (k17) . 460 Serviceability of Type 1 nailed connections. 461 Type 2 nailed connections . 462 Moment resisting nailed connections 464 Geometric details for nailed connections 466 Eccentricity of connections 458 Thickness of elements ..466 Detailing nailed connections .467 Nail spacings..469 Edge distance .469 End distance469 7.2.12 Design techniques for nailed connections .. 469 Design summaryNailed Type 1 connections 470 Design summaryNailed Type 2 connections 473 Detailing nailed connections .474 Example 7.1 Design of a spliced connection in a tension chord 475 7.3 STRENGTH AND SERVICEABILITY OF SCREWED CONNECTIONS .. 478 7.3.1 Capacity of Type 1 screwed connections .. 478 SA HB 1082013 Timber Design Handbook 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 xi Capacity of Type 2 screwed connections .. 479 Serviceability of Type 1 screwed connections 480 Moment resisting screwed connections .. 480 Comparison with nail capacities. 481 Designing and detailing screwed connections. 481 7.4 STRENGTH AND SERVICEABILITY OF BOLTED CONNECTIONS .. 483 Directionality of bolt strength484 7.4.1 Type 1 bolted connections . 484 Capacity factor..485 Modification factors ..485 7.4.2 7.4.3 7.4.4 7.4.5 7.4.6 Characteristic system capacity of bolts (Qsk) 486 Head fixity factor (k16) 487 Factor for multiple bolts (k17) . 488 Serviceability of Type 1 bolted connections 489 Type 2 bolted connections . 491 Length of bearing factor k7 493 7.4.7 Geometric details for bolted connections .. 493 Thickness of elements ..493 Spacing of bolts 495 Edge and end distances.495 Hole size ..495 Washer size.496 7.4.8 Design techniques for bolted connections . 496 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) Design summaryBolted Type 1 connections 497 Design summaryBolted Type 2 connections 500 Example 7.2 Bolted truss connection 500 7.5 STRENGTH OF COACH SCREWED CONNECTIONS . 505 7.5.1 Capacity of Type 1 coach screwed connections . 505 7.5.2 Capacity of Type 2 coach screwed connections . 506 7.5.3 Serviceability of Type 1 coach screwed connections.. 507 7.5.4 Designing and detailing coach screwed connections .. 507 7.6 STRENGTH AND SERVICEABILITY OF SPLIT-RING CONNECTORS . 508 7.6.1 Strength of Type 1 split-ring connections . 508 7.6.2 Characteristic capacity of split-rings (k15 k18 Qk) . 510 7.6.3 Serviceability of Type 1 split-ring connections.. 510 7.6.4 Limitations on the use of split-ring connections 510 7.6.5 Issues for maintenance of split-ring connections .. 511 7.7 STRENGTH AND SERVICEABILITY OF SHEAR-PLATE CONNECTORS 512 7.7.1 Strength of Type 1 shear-plate connections . 512 7.7.2 Characteristic capacity of shear-plates (k15 k18 Qk).. 513 7.7.3 Serviceability of Type 1 shear-plate connections.. 513 7.7.4 Limitations on the use of shear-plate connections. 514 7.7.5 Issues for maintenance of shear-plate connections 514 7.8 STRENGTH OF METAL DOWELS IN TYPE 1 CONNECTIONS .. 515 7.8.1 Metal dowelled fin plate connections .. 515 Connections 516 Timber members..516 Slots in timber members ..516 Metal fin plates .517 Holes ..518 Dowels ..518 7.8.2 Strength of Type 1 metal dowelled fin plate connections . 518 Capacity factor..519 Modification factors ..519 7.8.3 Characteristic system capacity of dowels (Qsk) .. 520 Example 7.3 System capacity - dowelled connection ..521 7.8.4 Head fixity factor (k16) 522 7.8.5 Serviceability of Type 1 fin plate connections 522 7.8.6 Geometric details for dowelled fin plate connections . 523 Clamping bolts..523 SA HB 1082013 xii Timber Design Handbook 7.8.7 Design techniques for dowelled fin plate connections 523 7.9 INJECTED EPOXY STEEL DOWEL CONNECTIONS .. 524 7.9.1 Load transfer mechanisms in epoxied dowel connections 525 7.9.2 Capacity of epoxied dowel connections . 526 7.9.3 Construction of epoxied dowel connections. 526 7.10 DETAILING CONNECTIONS . 527 7.10.1 Load transfer in a connection 527 7.10.2 Tension perpendicular to grain . 528 Reducing the risk of failure due to tension perpendicular to grain.529 7.10.3 Splitting characteristics of structural timbers 531 7.10.4 Eccentric loading . 532 7.11 SUMMARY OF CONNECTION CAPACITIES . 533 7.12 PRACTICE PROBLEMS 537 7.12.1 Short answer problems . 537 7.12.2 Calculation problems . 537 7.13 REFERENCES CHAPTER 7 541 APPENDIX A PROPERTIES OF TIMBER CROSS-SECTIONS. 543 APPENDIX B DESIGN PARAMETERS FOR SOME COMMON MEMBERS .. 547 Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) APPENDIX C NOTATION . 553 INDEX .. 557 SA HB 1082013 Timber Design Handbook xiii Accessed by UNIVERSITY OF QUEENSLAND on 16 Jan 2019 (Document currency not guaranteed when printed) FIGURES Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure 1.1 Trees .3 1.2 Cross-section of trunk .4 1.3 Failure characteristics of clear wood and structural timber .5 1.4 Cell structure of timber, magnified 250 times 6 1.5 Orthotropic nature of wood fibre ..7 1.6 Creep and duration of load effects 9 1.7 Nomenclature of timber used in housing 13 1.8 Distortion in timber 16 1.9 Slope of grain in timber18 1.10 Knots ..19 1.11 Correlation of properties with grading parameters .25 1.12 Derivation of properties from small clears..27 1.13 Derivation of properties from in-grade testing..27 1.14 Flow chart for design for durability 33 1.15 Fire-rated plasterboard to give fire protection to a timber frame.45 1.16 Loss of section due to fire 46 1.17 Plywood.50 1.18 Glulam beams.51 1.19 Laminated Veneer Lumber (LVL) ..52 1.20 Cross laminated timber (CLT) ..54 2.1 Design process .62 2.2 Loading on floor bearers .72 2.3 Contributing areas on supporting members ..73 2.4 Tributary area for a hip rafter in a roof 74 2.5 Example 2.1 - floor system 76 2.6 Example 2.1 - solution .78 2.7 Flow chart for finding strength limit states imposed loads 89 2.8 Wind pressure on a building .97 2.9 Terrain and structure height multiplier Mz,cat .101 2.10 Wind flow over hills.103 2.11 Building surfaces and nomenclature 104 2.12 Wind suctions on a roof at a snapshot in time 106 2.13 Combinations of internal and external pressures ..108 2.14 Wind load example - church in Perth..111 2.15 Snow loadings in sub-alpine and alpine regions 117 2.16 Snow loads example - lodge at Cradle Valley, Tasmania.121 2.17 Snow loads example results .123 2.18 Earthquake response of buildings and static analysis .129 2.19 Horizontal force distribution with position in building..131 2.20 Earthquake loads design example .133 2.21 Earthquake loads design example results..135 2.22 Roof truss anchorage example 149 2.23 Loads on a structure during its lifetime..150 2.24 Probability distribution of loads on a structure.

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