Structural Timber Design to Eurocode 5

Jack Porteous is a consulting engineer specialising in timber engineering. He is a Chartered Engineer, Fellow of the Institution of Civil Engineers and Member of the Institution of Structural Engineers. He is a member of the BSI committee B/525/5, which is responsible for the structural use of timber in the UK and for the production of UK input to EN 1995-1-1. He is a member of the editorial advisory panel of the ICE publication, Construction Materials and a visiting scholar and lecturer in timber engineering at Edinburgh Napier University.Abdy Kermani is the Professor of Timber Engineering and Director of the UK’s Centre for Timber Engineering at Edinburgh Napier University. He is a Chartered Engineer, Fellow of the Institution of Structural Engineers and Fellow of the Institute of Wood Science. He has served on the organising committees and editorial technical advisory boards of international journals and conferences on timber engineering and the innovative use of construction materials. He is the appointed principal consultant to several UK and European structural and timber engineering firms and manufacturing industries.

• Preface to the Second Edition xii1 Timber as a Structural Material 11.1 Introduction 11.2 The structure of timber 21.3 Types of timber 31.3.1 Softwoods 31.3.2 Hardwoods 41.4 Natural characteristics of timber 41.4.1 Knots 41.4.2 Slope of grain 51.4.3 Reaction wood 51.4.4 Juvenile wood 61.4.5 Density and annual ring widths 61.4.6 Conversion of timber 71.4.7 Seasoning 111.4.8 Seasoning defects 111.4.9 Cracks and fissures 111.4.10 Fungal decay 111.5 Strength grading of timber 111.5.1 Visual grading 121.5.2 Machine grading 121.5.3 Strength classes 151.6 Section sizes 161.7 Engineered wood products (EWPs) 161.7.1 Glued-laminated timber (glulam) 181.7.2 Cross-laminated timber (CLT or X-Lam) 201.7.3 Plywood 211.7.4 Laminated veneer lumber (LVL) 251.7.5 Laminated Strand Lumber (LSL), TimberStrand® 251.7.6 Parallel Strand Lumber (PSL), Parallam® 271.7.7 Oriented Strand Board (OSB) 271.7.8 Particleboards and fibre composites 391.7.9 Thin webbed joists (I-joists) 391.7.10 Thin webbed beams (box beams) 411.7.11 Structural Insulated Panels (SIPs) 421.8 Suspended timber flooring 441.9 Adhesive bonding of timber 461.10 Preservative treatment for timber 471.11 Fire safety and resistance 481.12 References 502 Introduction to Relevant Eurocodes 522.1 Eurocodes: General structure 522.2 Eurocode 0: Basis of structural design (EC0) 542.2.1 Terms and definitions (EC0, 1.5) 542.2.2 Basic requirements (EC0, 2.1) 552.2.3 Reliability management (EC0, 2.2) 562.2.4 Design working life (EC0, 2.3) 562.2.5 Durability (EC0, 2.4) 572.2.6 Quality management (EC0, 2.5) 582.2.7 Principles of limit state design: General (EC0, 3.1) 582.2.8 Design situations (EC0, 3.2) 582.2.9 Ultimate limit states (EC0, 3.3) 592.2.10 Serviceability limit states (EC0, 3.4) 592.2.11 Limit states design (EC0, 3.5) 602.2.12 Classification of actions (EC0, 4.1.1) 602.2.13 Characteristic values of actions (EC0, 4.1.2) 602.2.14 Other representative values of variable actions (EC0, 4.1.3) 612.2.15 Material and product properties (EC0, 4.2) 622.2.16 Structural analysis (EC0, 5.1) 622.2.17 Verification by the partial factor method: General (EC0, 6.1) 652.2.18 Design values of actions (EC0, 6.3.1) 652.2.19 Design values of the effects of actions (EC0, 6.3.2) 662.2.20 Design values of material or product properties (EC0, 6.3.3) 662.2.21 Factors applied to a design strength at the ULS 712.2.22 Design values of geometrical data (EC0, 6.3.4) 712.2.23 Design resistance (EC0, 6.3.5) 712.2.24 Ultimate limit states (EC0, 6.4.1–6.4.5) 732.2.25 Serviceability limit states: General (EC0, 6.5) 772.3 Eurocode 5: Design of Timber Structures – Part 1-1: General – Common Rules and Rules for Buildings (EC5) 792.3.1 General matters 792.3.2 Serviceability limit states (EC5, 2.2.3) 802.3.3 Load duration and moisture influences on strength (EC5, 2.3.2.1) 842.3.4 Load duration and moisture influences on deformations (EC5, 2.3.2.2) 842.3.5 Stress–strain relations (EC5, 3.1.2) 872.3.6 Size and stress distribution effects (EC5, 3.2, 3.3, 3.4 and 6.4.3) 872.3.7 System strength (EC5, 6.6) 902.4 Symbols 932.5 References 983 Using Mathcad® for Design Calculations 1003.1 Introduction 1003.2 What is Mathcad? 1003.3 What does Mathcad do? 1013.3.1 A simple calculation 1013.3.2 Definitions and variables 1023.3.3 Entering text 1023.3.4 Working with units 1033.3.5 Commonly used Mathcad functions 1043.4 Summary 1063.5 References 1064 Design of Members Subjected to Flexure 1074.1 Introduction 1074.2 Design considerations 1074.3 Design value of the effect of actions 1094.4 Member span 1094.5 Design for Ultimate Limit States (ULS) 1104.5.1 Bending 1104.5.2 Shear 1214.5.3 Bearing (compression perpendicular to the grain) 1274.5.4 Torsion 1314.5.5 Combined shear and torsion 1334.6 Design for Serviceability Limit States (SLS) 1334.6.1 Deformation 1344.6.2 Vibration 1374.7 References 1424.8 Examples 1435 Design of Members and Walls Subjected to Axial or Combined Axial and Flexural Actions 1585.1 Introduction 1585.2 Design considerations 1585.3 Design of members subjected to axial actions 1605.3.1 Members subjected to axial compression 1605.3.2 Members subjected to compression at an angle to the grain 1705.3.3 Members subjected to axial tension 1725.4 Members subjected to combined bending and axial loading 1745.4.1 Where lateral torsional instability due to bending about the major axis will not occur 1745.4.2 Lateral torsional instability under the effect of bending about the major axis 1785.4.3 Members subjected to combined bending and axial tension 1795.5 Design of stud walls 1795.5.1 Design of load-bearing walls 1805.5.2 Out of plane deflection of load-bearing stud walls (and columns) 1865.6 References 1885.7 Examples 1896 Design of Glued-Laminated Members 2166.1 Introduction 2166.2 Design considerations 2186.3 General 2186.3.1 Horizontal and vertical glued-laminated timber 2186.3.2 Design methodology 2196.4 Design of glued-laminated members with tapered, curved or pitched curved profiles (also applicable to LVL members) 2236.4.1 Design of single tapered beams 2236.4.2 Design of double tapered beams, curved and pitched cambered beams 2286.4.3 Design of double tapered beams, curved and pitched cambered beams subjected to combined shear and tension perpendicular to the grain 2346.5 Finger joints 234Annex 6.1 Deflection formulae for simply supported tapered and double tapered beams subjected to a point load at mid-span or to a uniformly distributed load. 234Annex 6.2 Graphical representation of factors k§¤ and kp used in the derivation of the bending and radial stresses in the apex zone of double tapered curved and pitched cambered beams. 2376.6 References 2386.7 Examples 2397 Design of Composite Timber and Wood-Based Sections 2587.1 Introduction 2587.2 Design considerations 2597.3 Design of glued composite sections 2607.3.1 Glued thin webbed beams 2607.3.2 Glued thin flanged beams (stressed skin panels) 2747.4 References 2837.5 Examples 2838 Design of Built-Up Columns 3118.1 Introduction 3118.2 Design considerations 3118.3 General 3128.4 Bending stiffness of built-up columns 3138.4.1 The effective bending stiffness of built-up sections about the strong (y–y) axis 3148.4.2 The effective bending stiffness of built-up sections about the z–z axis 3168.4.3 Design procedure 3188.4.4 Built-up sections – spaced columns 3238.4.5 Built-up sections – latticed columns 3278.5 Combined axial loading and moment 3318.6 Effect of creep at the ULS 3328.7 References 3338.8 Examples 3339 Design of Stability Bracing, Floor and Wall Diaphragms 3579.1 Introduction 3579.2 Design considerations 3589.3 Lateral bracing 3589.3.1 General 3589.3.2 Bracing of single members (subjected to direct compression) by local support 3609.3.3 Bracing of single members (subjected to bending) by local support 3639.3.4 Bracing for beam, truss or column systems 3649.4 Floor and roof diaphragms 3689.4.1 Limitations on the applicability of the method 3689.4.2 Simplified design procedure 3689.5 The in-plane racking resistance of timber walls under horizontal and vertical loading 3709.6 References 3729.7 Examples 37310 Design of Metal Dowel-type Connections 38310.1 Introduction 38310.1.1 Metal dowel-type fasteners 38310.2 Design considerations 38710.3 Failure theory and strength equations for laterally loaded connections formed using metal dowel fasteners 38910.3.1 Dowel diameter 39510.3.2 Characteristic fastener yield moment (My,Rk) 39710.3.3 Characteristic embedment strength (fh,k) 39810.3.4 Member thickness, t1 and t2 40210.3.5 Friction effects and axial withdrawal of the fastener 40310.3.6 Brittle failure 40610.4 Multiple dowel fasteners loaded laterally 41210.4.1 The effective number of fasteners 41310.4.2 Alternating forces in connections 41610.5 Design strength of a laterally loaded metal dowel connection 41610.5.1 Loaded parallel to the grain 41610.5.2 Loaded perpendicular to the grain 41710.6 Examples of the design of connections using metal dowel-type fasteners 41810.7 Multiple shear plane connections 41810.8 Axial loading of metal dowel connection systems 42010.8.1 Axially loaded nails 42010.8.2 Axially loaded bolts 42310.8.3 Axially loaded dowels 42310.8.4 Axially loaded screws 42310.9 Combined laterally and axially loaded metal dowel connections 42710.10 Lateral stiffness of metal dowel connections at the SLS and ULS 42810.11 Frame analysis incorporating the effect of lateral movement in metal dowel fastener connections 43510.12 References 43610.13 Examples 43711 Design of Joints with Connectors 47311.1 Introduction 47311.2 Design considerations 47311.3 Toothed-plate connectors 47411.3.1 Strength behaviour 47411.4 Ring and shear-plate connectors 48011.4.1 Strength behaviour 48011.5 Multiple shear plane connections 48711.6 Brittle failure due to connection forces at an angle to the grain 48711.7 Alternating forces in connections 48711.8 Design strength of a laterally loaded connection 48811.8.1 Loaded parallel to the grain 48811.8.2 Loaded perpendicular to the grain 48911.8.3 Loaded at an angle to the grain 48911.9 Stiffness behaviour of toothed-plate, ring and shear-plate connectors 48911.10 Frame analysis incorporating the effect of lateral movement in connections formed using toothed-plate, split-ring or shear-plate connectors 49111.11 References 49111.12 Examples 49112 Moment Capacity of Connections Formed with Metal Dowel Fasteners or Connectors 50412.1 Introduction 50412.2 Design considerations 50512.3 The effective number of fasteners in a row in a moment connection 50512.4 Brittle failure 50612.5 Moment behaviour in timber connections: Rigid model behaviour 50712.5.1 Assumptions in the connection design procedure 50712.5.2 Connection design procedure 50912.5.3 Shear strength and force component checks on connections subjected to a moment and lateral forces 51212.6 The analysis of structures with semi-rigid connections 51912.6.1 The stiffness of semi-rigid moment connections 52012.6.2 The analysis of beams with semi-rigid end connections 52212.7 References 52612.8 Examples 52613 Racking Design of Multi-storey Platform Framed Wall Construction 55513.1 Introduction 55513.2 Conceptual design 55513.3 Design requirements of racking walls 55813.4 Loading 55813.5 Basis of Method A 56013.5.1 General requirements 56013.5.2 Theoretical basis of the method 56213.5.3 The EC5 procedure 56413.6 Basis of the racking method in PD6693-1 57313.6.1 General requirements 57313.6.2 Theoretical basis of the method 57513.6.3 The PD6693-1 procedure 57913.7 References 58613.8 Examples 587Appendix A: Weights of Building Materials 610Appendix B: Related British Standards for Timber Engineering in Buildings 612Appendix C: Possible Revisions to be Addressed in a Corrigendum to EN 1995-1-1:2004 + A1:2008 614Index 618The Example Worksheets Order Form 624