STRUCTURAL TIMBER DESIGN

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STRUCTURAL TIMBER DESIGN to Eurocode 5 2nd Edition Jack Porteous BSc, MSc, DIC, PhD, CEng, MIStructE, FICE Director lack Porteous Consultancy and Abdy Kernlani BSc,

1 STRUCTURAL TIMBER DESIGN to Eurocode 5 2nd Edition Jack Porteous BSc, MSc, DIC, PhD, CEng, MIStructE, FICE Director lack Porteous Consultancy and Abdy Kernlani BSc, MSc, PhD, CEng, FIStructE, FIWSc Professor and Director ofcentre for Timber Engineering Edinburgh Napier University ~WILEY-BLACKWELL A John Wiley & Sons, Ltd., Publication

Contents Pre/ace to the Second Edition 1 Timber as a Structural Material 1.1 Introduction 1.2 The structure of timber 1.3 Types of timber 1.3.1 Softwoods 1.3.2 Hardwoods 1.

2 Contents Pre/ace to the Second Edition 1 Timber as a Structural Material 1.1 Introduction 1.2 The structure of timber 1.3 Types of timber Softwoods Hardwoods 1.4 Natural characteristics of timber Knots Slope of grain Reaction wood Juvenile wood Density and annual ring widths Conversion of timber Seasoning Seasoning defects Cracks and fissures Fungal decay 1.5 Strength grading of timber Visual grading Machine grading Strength classes 1.6 Seetion sizes 1.7 Engineered wood products (EWPs) Glued-laminated timber (glulam) Cross-Iaminated timber (CLT or X-Lam) Plywood Laminated Veneer Lumber (LVL) Laminated Strand Lumber (LSL), TimberStrand Parallel Strand Lumber (PSL), Parallam Oriented Strand Board (OSB) Particleboards and fibre composites Thin webbedjoists (l-joists) Thin webbed beams (box beams) Structural Insulated Panels (SIPs) 1.8 Suspended timber t16örih~ "';\\' ~ i,' :! 'h'\j 1.9 Adhesive bonding of timber,nt':,i,., I;' i"i' xii II 11 II v

vi Contents 1.10 Preservative treatment for timber 1.1 I Fire safety and resistance 1.12 References 47 48 50 2 Introduction to Relevant Eurocodes 52 2.1 Eurocodes: General structure 52 2.

3 vi Contents 1.10 Preservative treatment for timber 1.1 I Fire safety and resistance 1.12 References Introduction to Relevant Eurocodes Eurocodes: General structure Eurocode 0: Basis of structural design (ECO) Terms and definitions (ECO, 1.5) Basic requirements (ECO, 2.1) Reliability management (ECO, 2.2) Design working life (ECO, 2.3) Durability (ECO, 2.4) Quality management (ECO, 2.5) Principles of limit state design: General (ECO, 3.1) Design situations (ECO, 3.2) Ultimate limit states (ECO, 3.3) Serviceability limit states (ECO, 3.4) Limit states design (ECO, 3.5) Classification of actions (ECO, 4.1.1) I3 Characteristic values of actions (ECO, 4.1.2) Other representative values of variable actions (ECO, 4.1.3) Material and product properties (ECO, 4.2) Structural analysis (ECO, 5.1) Verification by the partial factor method: General (ECO, 6.1) Design values of actions (ECO, 6.3.1) I9 Design values of the effects of actions (ECO, 6.3.2) Design values of material or product properties (ECO, 6.3.3) I Factors applied to a design strength at the ULS Design values of geometrical data (ECO, 6.3.4) Design resistance (ECO, 6.3.5) Ultimate limit states (ECO, ) Serviceability limit states: General (ECO, 6.5) Eurocode 5: Design oftimber Structures - Part 1-1: General- Common Rules and Rules for Buildings (EC5) I General matters Serviceability limit states (EC5, 2.2.3) Load duration and moisture influences on strength (EC5, ) Load duration and moisture influences on deformations (EC5, ) Stress-strain relations (EC5, 3.1.2) Size and stress distribution effects (EC5, 3.2, 3.3, 3.4 and 6.4.3) System strength (EC5. 6.6) Symbols References 98 3 Using Mathcad for Design Calculations Introduction What is Mathcad? 100

Contents vii 3.3 What does Mathcad do? 3.3.1 A simple calculation 3.3.2 Definitions and variables 3.3.3 Entering text 3.3.4 Working with units 3.3.5 Commonly used Mathcad functions 3.4 Summary 3.

4 Contents vii 3.3 What does Mathcad do? A simple calculation Definitions and variables Entering text Working with units Commonly used Mathcad functions 3.4 Summary 3.5 References Design of Members Subjected to Flexure Introduction Design considerations Design value of the effect of actions Member span Design for Ultimate Limit States (ULS) Bending Shear Bearing (compression perpendicular to the grain) Torsion Combined shear and torsion Design for Serviceability Limit States (SLS) Deformation Vibration References Examples Design of Members and Walls Subjected to Axial or Combined Axial and Flexural Actions Introduction Design considerations Design of members subjected to axial actions Members subjected to axial compression Members subjected to compression at an angle to the grain Members subjected to axial tension Members subjected to combined bending and axialloading Where lateral torsional instability due to bending about the major axis will not occur Lateral torsional instability under the effect of bending about the major axis Members subjected to combined bending and axial tension Design of stud walls Design of load-bearing walls Out ofplane deflection of load-bearing stud walls (and columns) References Examples Design of Glued-Laminated Members Introduction Design considerations 218

viii Contents 6.3 General 2 I8 6.3.1 Horizontal and vertical glued-iaminated timber 218 6.3.2 Design methodology 219 6.

5 viii Contents 6.3 General 2 I Horizontal and vertical glued-iaminated timber Design methodology Design of glued-iaminated members with tapered, curved or pitched curved profiles (also applicable to LVL members) I Design of single tapered beams Design of double tapered beams, curved and pitched cambered beams Design of double tapered beams, curved and pitched cambered beams subjected to combined shear and tension perpendicular to the grain Finger joints 234 Annex 6. I Deflection formulae for simply supported tapered and double tapered beams subjected to a point load at mid-span or to a uniformly distributed load. 234 Annex 6.2 Graphical representation of factors k r and k p used in the derivation of the bending and radial stresses in the apex zone of double tapered curved and pitched cambered beams References Examples Design ofcomposite Timber and Wood-Based Sections Introduction Design considerations Design of glued composite seetions I Glued thin webbed beams Glued thin flanged beams (stressed skin panels) References Examples Design of Built-Up Columns Introduction Design considerations 3 I General Bending stiffness of built-up columns 3I The effective bending stiffness of built-up sections about the strong (y-y) axis The effective bending stiffness of built-up seetions about the z-z axis Design procedure BuiIt-up seetions - spaced columns Built-up sections -latticed columns Combined axial loading and moment 33 I 8.6 Effect of creep at the ULS References Examples Design of Stability Bracing, Floor and Wall Diaphragms Introduction Design considerations 358

Contents ix 9.3 Lateral bracing 358 9.3.1 General 358 9.3.2 Bracing of single members (subjected to direct compression) by local support 360 9.3.3 Bracing of single members (subjected to bending) by local support 363 9.

6 Contents ix 9.3 Lateral bracing General Bracing of single members (subjected to direct compression) by local support Bracing of single members (subjected to bending) by local support Bracing for beam, truss or column systems Floor and roof diaphragms Limitations on the applicability ofthe method Simplified design procedure The in-plane racking resistance of timber walls under horizontal and verticalloading References Examples Design of Metal Dowel-type Connections Introduction Metal dowel-type fasteners Design considerations Failure theory and strength equations for laterally loaded connections formed using metal dowel fasteners Dowel diameter Characteristic fastener yield moment (MV,Rk) Characteristic embedment strength (!u) Member thickness, t l and t Friction effects and axial withdrawal of the fastener Brittle failure Multiple dowel fasteners loaded laterally The effective number of fasteners Alternating forces in connections Design strength of a laterally loaded metal dowel connection Loaded parallel to the grain Loaded perpendicular to the grain Examples of the design ofconnections using metal dowel-type fasteners Multiple shear plane connections Axialloading of metal dowel connection systems Axially loaded nails Axially loaded bolts Axially loaded dowels Axially loaded screws Combined laterally and axially loaded metal dowel connections Lateral stiffness of metal dowel connections at the SLS and ULS Frame analysis incorporating the effect of lateral movement in metal dowel fastener connections References Examples Design ofjoints with Connectors Introduction Design considerations 473

x Contents 11.3 Toothed-plate connectors 474 11.3.1 Strength behaviour 474 11.4 Ring and shear-plate connectors 480 11.4.1 Strength behaviour 480 11.5 Multiple shear plane connections 487 11.

7 x Contents 11.3 Toothed-plate connectors Strength behaviour Ring and shear-plate connectors Strength behaviour Multiple shear plane connections Brittle failure due to connection forces at an angle to the grain Alternating forces in connections Design strength of a laterally loaded connection Loaded parallel to the grain Loaded perpendicular to the grain Loaded at an angle to the grain Stiffness behaviour of toothed-plate, ring and shear-plate connectors Frame analysis incorporating the effect oflateral movement in connections formed using toothed-plate, split-ring or shear-plate connectors 491 1l.l1 References Examples Moment Capacity of Connections Formed with Metal Dowel Fasteners or Connectors Introduction Design considerations The effective number of fasteners in a row in a moment connection Brittle failure Moment behaviour in timber connections: Rigid model behaviour Assumptions in the connection design procedure Connection design procedure Shear strength and force component checks on connections subjected to a moment and lateral forces The analysis of structures with semi-rigid connections The stiffness of semi-rigid moment connections The analysis of beams with semi-rigid end connections References Examples Racking Design of Multi-storey Platform Framed Wall Construction lntroduction Conceptual design Design requirements of racking walls Loading Basis of Method A General requirements Theoretical basis of the method The EC5 procedure Basis of the racking method in PD General requirements Theoretical basis of the method The PD procedure 579

8 Contents xi 13.7 References 13.8 Examp1es Appendix A: Weights ofbuilding Materials Appendix B: Related British Standardsfor Timber Engineering in Buildings Appendix C: Possible Revisions to be Addressed in a Corrigendum to EN :2004 +Al:200S Index The Example Worksheets Order Form

Structural Timber Design

2nd Edition 2nd Edition 2nd Edition Structural Timber Design Jack Porteous and Abdy Kermani The Authors Abdy Kermani is the Professor of Timber Engineering and Director of the UK s Centre for Timber Engineering