Concise Eurocodes: Design of Timber Structures€¦ · · 2012-10-19Concise Eurocodes: Design of Timber Structures: ... Concise Eurocodes: Design of Timber Structures BS EN 1995:

Concise Eurocodes: Design of Timber Structures

This is a sample chapter from Concise Eurocodes: Design of Timber Structures. To read more and buy, visit http://shop.bsigroup.com/bip2198 © BSI British Standards Institution

This book is one of a series of books which currently comprises the following:

Concise Eurocodes: Loadings On Structures BS EN 1991: Eurocodes 1 (BSI ref BIP ref 2199)

Concise Eurocodes: Design of Timber Structures: BS EN 1995: Eurocodes 5 (BSI ref BIP ref 2198)

Concise Eurocodes: Geotechnics BS EN 1997: Eurocodes 7 (BSI ref BIP ref 2205)



BS EN 1995: Eurocode 5

Julian Marcroft


First published in the UK in 2011 by BSI

389 Chiswick High Road London W4 4AL

© British Standards Institution 2011

All rights reserved. Except as permitted under the Copyright, Designs and Patents Act 1988, no part of this publication may be reproduced, stored in a retrieval system

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Whilst every care has been taken in developing and compiling this publication, BSI accepts no liability for any loss or damage caused, arising directly or indirectly in connection with

reliance on its contents except to the extent that such liability may not be excluded in law.

The right of Julian Marcroft to be identified as the author of this Work has been asserted by him in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988.

Typeset in Frutiger by Monolith – http://www.monolith.uk.com Printed in Great Britain by Berforts Group. www.berforts.com

British Library Cataloguing in Publication DataA catalogue record for this book is available from the British Library

ISBN 978 0 580 69452 3


Concise Eurocodes: Design of Timber Structures v

Contents

Foreword vii

BS EN 1995-1-1: Eurocode 1 Section 1 Wind loading 1

1.1 Scope 1

1.2 Normative references 1

1.3 Terms and definitions 3

1.4 Symbols 4

BS EN 1995-1-1: Eurocode 1 Section 2 Basis of design 10

2.1 Basic requirements 10

2.2 Principles of limit state design 10

2.3 Design values 11

2.4 Ultimate limit states 12

2.5 Serviceability limit states 15

2.6 Basic variables 16

2.7 Partial factors for material properties and resistances 18

2.8 System strength 19

BS EN 1995-1-1: Eurocode 1 Section 3 Material properties 20

3.1 Strength modification factors for service classes and load-duration classes 20

3.2 Deformation modification factors for service classes 21

3.3 Solid timber 21

3.4 Glued laminated timber 22

3.5 Laminated veneer lumber (LVL) 22

3.6 Wood-based panels 23

3.7 Adhesives 23

3.8 Metal fasteners 24

BS EN 1995-1-1: Eurocode 1 Section 4 Durability 25

4.1 Resistance to biological organisms 25

4.2 Resistance to corrosion 25

BS EN 1995-1-1: Eurocode 1 Section 5 Basis of structural analysis 26

5.1 General 26

5.2 Effective cross-section at a joint 26

5.3 Trusses 26

BS EN 1995-1-1: Eurocode 1 Section 6 Ultimate limit states 28

6.1 Design of cross-sections subjected to stress in one principal direction 28



Contents

vi

6.2 Design of cross-sections subjected to combined stresses 33

6.3 Members with notches and holes 36

BS EN 1995-1-1: Eurocode 1 Section 7 Serviceability limit states 39

7.1 Limiting values for deflections of beams 39

7.2 Vibrations in residential floors 40

BS EN 1995-1-1: Eurocode 1 Section 8 Connections with metal fasteners and connectors 42

8.1 Connections made with metal dowel-type fasteners 42

8.2 Connections made with split-ring or shear-plate connectors 58

BS EN 1995-1-1: Eurocode 1 Section 9 Components and assemblies 63

9.1 Glued thin-webbed beams 63

9.2 Trusses 63

9.3 Roof and floor diaphragms 64

9.4 Wall diaphragms 65

9.5 Bracing 72

BS EN 1995-1-1: Eurocode 1 Section 10 Structural detailing and control 75

10.1 General 75

10.2 Materials 75

10.3 Glued joints 75

10.4 Connections with mechanical fasteners 76

10.5 Assembly 77

10.6 Transportation and erection 77

10.7 Control 77

10.8 Special rules for diaphragm structures 78

Annex A: Characteristic strengths and moduli for timber and wood-based materials 80

Annex B: Methods, in accordance with BS EN 1991-1-7 (and its National Annex), for designing platform timber-frame buildings to sustain an extent of localised damage from an unspecified cause without disproportionate collapse 87

Annex C: Cross-referencing between Concise Eurocode 5 clauses and the associated clauses in BS EN 1995-1-1, NA to BS EN 1995-1-1, BS EN 1990, NA to BS EN 1990, BS EN 1991-1-1 and PD 6693-1-1 91


Concise Eurocodes: Design of Timber Structures vii

Foreword

For consulting engineers the transition in structural design procedures from a British Standard to the replacement Eurocode constitutes a major programme of work for any construction material. In the case of timber this transition is made more problematic by the proliferation of BS EN documentation required by a designer as well as because for many consulting engineers timber is a minority-use structural material at a time when the switch to Eurocodes is being made simultaneously for all construction materials.

Concise Eurocode 5 is intended to assist consulting engineers by providing a briefer and more accessible presentation of the design procedures associated with BS EN 1995-1-1: Eurocode 5: Design of Timber Structures encompassing the following features:

a) It is laid out in the same Code format as the Eurocodes and maintains the same 10 sections as BS EN 1995-1-1 albeit with most sections being reduced in length.

b) Unlike BS EN 1995-1-1 it does not cover the less frequently used components (e.g. tapered or curved glued laminated beams) or fasteners (e.g. staples) as well as not addressing the more complex analytical techniques (e.g. second-order effects).

c) It directly incorporates the Nationally Determined Parameters of the National Annex to BS EN 1995-1-1 as well as some of the more important non-contradictory complementary information (NCCI) of PD 6693-1-1.

d) Its section 2 ‘Basis of design’ has been extended to include the essential requirements (e.g. load combination rules) of BS EN 1990 (and its National Annex).

e) The characteristic values of the structural properties of the more commonly used wood-based materials, currently found in BS EN product standards, have been included in its Annex A.

f) Concise Eurocode 5 is broadly half the length of BS EN 1995-1-1.

Concise Eurocode 5 in Annex C cross-references its clauses to the associated clauses in BS EN 1995-1-1 (or its National Annex), BS EN 1990 (or its National Annex) or PD 6693-1-1.

The raison d’être for Concise Eurocode 5 is intended to be accessibility to the design procedures pertaining to BS EN 1995-1-1 rather than explanation of the design procedures of BS EN 1995-1-1. However, notwithstanding this, in Annex D, two design examples are presented covering design aspects where BS EN 1995-1-1 is markedly different from BS 5268.

NOTE This book provides informative commentary on BS EN 1995. However, compliance with the Eurocodes can only be ensured by careful use of the complete version of the official Eurocodes and associated documentation.



Concise Eurocodes: Design of Timber Structures 1

Source reference

BS EN 1995-1-1: Eurocode 1 Section 1 Wind loading

1.1 Scope

(1) Concise Eurocode 5 applies to the design of buildings in timber (solid timber, sawn or planed, glued laminated timber or wood-based structural products, e.g. LVL) or wood-based panels jointed together with adhesives or metal fasteners. It complies with the principles and requirements for the safety and serviceability of structures and the basis of design and verification given in BS EN 1990.

(2) Concise Eurocode 5 is only concerned with requirements for structural resistance, serviceability and durability.

(3) The following subjects are dealt with in Concise Eurocode 5:

Section 1: GeneralSection 2: Basis of designSection 3: Material propertiesSection 4: DurabilitySection 5: Basis of structural analysisSection 6: Ultimate limit statesSection 7: Serviceability limit statesSection 8: Connections with metal fasteners and connectorsSection 9: Components and assembliesSection 10: Structural detailing and control

1.2 Normative references

BS EN 300 Oriented Strand Board (OSB) – Definition, classification and specifications

BS EN 301 Adhesives, phenolic and aminoplastic for load-bearing timber structures; classification and performance requirements

BS EN 312 Particleboards – Specifications BS EN 335-1 Durability of wood and wood-based products – definition

of hazard classes of biological attack. Part 1: GeneralBS EN 335-2 Durability of wood and wood-based products – definition

of hazard classes of biological attack. Part 2: Application to solid wood

EC 5-1-1, 1.1.1(1)

EC 5-1-1, 1.1.1(2)

EC 5-1-1, 1.1.2(2)

EC 5-1-1, 1.2



Section 1 Wind loading

2

Source reference

BS EN 335-3 Durability of wood and wood-based products – Definition of hazard classes of biological attack. Part 3: Application to wood-based panels

BS EN 350-2 Durability of wood and wood-based products – Natural durability of solid wood. Part 2: Guide to natural durability and treatability of selected wood species of importance in Europe

BS EN 351-1 Durability of wood and wood-based products – Preservative treated solid wood. Part 1: Classification of preservative penetration and retention

BS EN 385 Finger jointed structural timber. Performance requirements and minimum production requirements

BS EN 409 Timber structures – Test methods. Determination of the yield moment of dowel-type fasteners – Nails

BS EN 460 Durability of wood and wood-based products – Natural durability of solid wood – Guide of the durability requirements for wood to be used in hazard classes

BS EN 594 Timber structures – Test methods – Racking strength and stiffness of timber frame wall panels

BS EN 636 Plywood – Specifications BS EN 912 Timber fasteners – Specifications for connectors for

timberBS EN 1382 Timber structures – Test methods – Withdrawal capacity

of timber fastenersBS EN 1383 Timber structures – Test methods – Pull through testing

of timber fastenersBS EN 1990 Eurocode – Basis of structural design BS EN 1991-1-1 Eurocode 1: Actions on structures – Part 1-1: General

actions – Densities, self-weight and imposed loadsBS EN 1991-1-3 Eurocode 1: Actions on structures – Part 1-3: General

actions – Snow loadsBS EN 1991-1-4 Eurocode 1: Actions on structures – Part 1-4: General

actions – Wind actionsBS EN 1991-1-7 Eurocode 1: Actions on structures – Part 1-7: General

actions – Accidental actionsBS EN 10147 Specification for continuously hot-dip zinc-coated

structural steel sheet and strip – Technical delivery conditions

BS EN 13986 Wood-based panels for use in construction – Characteristics, evaluation of conformity and marking

BS EN 14080 Timber structures – Glued laminated timber – Requirements




3

Source reference

BS EN 14081-1 Timber structures – Strength graded structural timber with rectangular cross-section – Part 1, General requirements

BS EN 14374 Timber structures – Structural laminated veneer lumber – Requirements

BS EN 14545 Timber structures – Connectors – RequirementsBS EN 14592 Timber structures – Fasteners – RequirementsBS EN 15425 Adhesives, one component polyurethane, for

load bearing timber structures – Classification and performance requirements

BS EN ISO 1461 Hot dip galvanized coatings on fabricated iron and steel articles – Specifications and test methods

1.3 Terms and definitions

1.3.1 Characteristic value

Refer to Annex A.

1.3.2 Equilibrium moisture content

The moisture content at which wood neither gains nor loses moisture to the surrounding air.

1.3.3 Fibre saturation point

Moisture content at which the wood cells are completely saturated.

1.3.4 Moisture content

The mass of water in wood expressed as a proportion of its oven-dry mass.

1.3.5 Racking

Effect caused by horizontal actions in the plane of a wall.

1.3.6 Racking discontinuities

Racking discontinuities in a wall are either door openings or large window openings whose dimensions exceed stipulated limits.

EC 5-1-1, 1.5




4

Source reference

1.3.7 Racking wall

A racking wall is a sheathed timber-frame wall located in a direction parallel to the wind (or other form of horizontal) load, commonly extending between return walls. A racking wall may comprise a single wall diaphragm or, if it contains racking discontinuities, may comprise more than one wall diaphragm.

1.3.8 Slip modulus

A property used in the calculation of the deformation between two members of a structure.

1.3.9 Wall diaphragm

A wall diaphragm is a length of racking wall between racking discontinuities. It may contain no window openings or alternatively may contain fully framed window openings of dimensions less than stipulated limits. A wall diaphragm may comprise a single wall panel or alternatively may contain more than one wall panel, provided that the connection between adjacent wall panels has been designed to provide adequate vertical shear resistance.

1.3.10 Wall panel

A wall panel consists of timber framing connected on one or both faces to wood-based sheathing sheets. Within the length of a wall panel adjacent sheathing sheets should be connected to the same wall stud.

1.4 Symbols

For the purpose of Concise Eurocode 5, the following symbols apply.

Latin upper case letters

Ad Design value of accidental actionAef Effective contact area in compression perpendicular to grainC Minimum spring stiffness at bracing supportCd Limiting design value of a serviceability criterionE0.05 Fifth percentile value of modulus of elasticity parallel to grainEd Design value of effect of action;Ed,dst Design value of the effect of destabilizing actionsEd,stb Design value of the effect of stabilizing actions(EI )b Floor flexural rigidity perpendicular to the joists

EC 5-1-1, 1.6




5

Source reference

(EI )joist Bending stiffness of a floor joist(EI )ℓ Longitudinal floor bending stiffnessF90,Rd Design splitting capacityF90,Rk Characteristic splitting capacityFc,90,d Design compressive load perpendicular to grainFd Design value of actionFd,b Design stabilizing force at each bracing supportFf,Rd Design lateral capacity of an individual wall sheathing fastenerFi,v,Rd Design racking strength of a wall diaphragmFk Characteristic value of actionFt,d Minimum resistance in any direction of a joint in a trussFv,0,Rk Characteristic load-carrying capacity of the connector for a

force parallel to grainFv,α,Rk Characteristic load-carrying capacity of the connector for a

force at angle α to grainFv,Ed Design shear force on side of connectionFv,ef,Rk Effective characteristic load-carrying capacity for one row

of fastenersFv,Rd Design racking strength of a racking wallFv,Rk Characteristic load-carrying capacity per shear plane per

fastenerGk,j Characteristic values of permanent actionsH Height of wall diaphragmKi,w Modification factor for wall length, vertical load and

holding-down arrangements;Kopening Modification factor taking into account the effect of

fully-framed window openingsKser Slip modulus per shear plane per fastenerL Length of wall diaphragmLt Overall length of trussLef Effective length of beamMd Maximum design moment acting on beamMhole,d Design moment acting on the beam at the hole centreMstb Stabilizing moment for the wall diaphragm from net dead loadMstb,lim Limiting value of stabilizing moment for the wall diaphragm

from net dead loadMy,Rk Characteristic fastener yield momentNd Mean compressive force in element requiring bracingQk,i Characteristic values of variable actionsRd Design value of load-carrying capacity or material strength

propertyRk Characteristic value of load-carrying capacity or material

strength propertyVd Design shear forceVhole,d Design shear force acting on the beam at the hole centre




6

Source reference

Latin lower case letters

a Limit for unit point load deflectiona1 Spacing of fasteners within one row parallel to graina2 Spacing of fasteners within one row perpendicular to graina3,t Distance between fastener and loaded enda3,c Distance between fastener and unloaded enda4,t Distance between fastener and loaded edgea4,c Distance between fastener and unloaded edgeab Bay length between bracing supportsad Design value of geometric data (e.g. span, member dimension)b Member widthbd Diaphragm widthbef Effective width of member taking into account the influence

of cracksd Fastener diameter d1 Diameter of centre hole of connectordc Connector diameterdh Nail head diameterdhole Diameter of holedit Screw inner thread diameterf1 Fundamental frequencyfax,k Characteristic pointside withdrawal strengthfc,0,d Design compressive strength parallel to grainfc,0,k Characteristic compressive strength parallel grainfc,90,d Design compressive strength perpendicular to grainfc,α,d Design compressive strength at an angle α to grainfhead,k Characteristic headside pull-through strengthfh,k Characteristic embedment strengthfm,k Characteristic bending strengthfm,y,d Design bending strength about the (strong) y-axisfm,z,d Design bending strength about the (weak) z-axisfp Design shear capacity per unit length of perimeter

sheathing fastenersft,0,d Design tensile strength parallel to grainft,0,k Characteristic tensile strength parallel grainft,90,d Design tensile strength perpendicular to grainfu,k Characteristic tensile strength of the fastenerfv,d Design shear strengthh Member depthhe Loaded edge distance to the centre of the most distant

fastenerhef Effective (reduced) depth in notched beamshemb Embedment depth of the connectork1 – k4 Modification factors for split-ring or shear plate connectors




7

Source reference

k90 Embedment strength modification factor for all angles to grain other than 0°

ka1 Reduction factor for the minimum spacing a1 parallel to grain;

ka2 Reduction factor for the minimum spacing a2 perpendicular to grain

kamp Amplification factor to account for shear or slip deflectionskc,90 Modification factor for compression strength perpendicular

to grainkcr Factor to take account of effect of cracks on shear strengthkcrit Factor which takes into account reduced bending strength

due to lateral bucklingkc,y , kc,z Factors taking account of reduced compression strength due

to lateral bucklingkd Modification factor for screw diameterkdef Deformation factor taking into account duration of load and

moisture contentkdist Proportion of load acting on a single joistkf Bracing modification factorkh Depth factor for bending and tensile strengthkl Length factor for LVL tensile strengthkℓ Bracing length modification factorkm Bi-axial bending factorkmod Modification factor for the effect of duration of load and

moisture contentkn Material constant for evaluation of shear strength in

notched beamskrope Rope effect modification factorkshape Factor accounting for effect of shape of the cross-section on

torsional strengthkstrut Factor to account for stiffness contribution of floor struttingksys System strength factorkv Reduction factor for shear strength of notched beamsky , kz Factors for evaluation of reduced compression strength due

to lateral bucklingl Member length (for LVL)ℓ Span or length of cantileverℓb Overall span of the stabilizing systemℓd Floor or roof diaphragm span ℓeq Equivalent floor span ℓthr Length of the threaded part in the pointside memberm Mass of floor corresponding to permanent actions onlymt Threshold mass of floor for fundamental frequency calculationn Number of fasteners/connectors in the rownef Effective number of fasteners/connectors in a row




8

Source reference

np Number of parallel membersp Proportion of wall diaphragm occupied by window openingsqd Design internal stability load per unit lengths Size effect exponent for LVLsj Floor joist spacingsn Wall sheathing perimeter fastener spacingt Thickness of OSB or particleboard (embedment strength

calculations)t1 Headside member thicknesst2 Central member thickness for double shear connections or

pointside penetration for single shear connectionstpen Pointside penetration or the length of the threaded part in

the pointside memberucreep Creep deformationufin Final deformationufin,G Final deformation for permanent actionufin,Q Final deformation for variable actionuinst Instantaneous deformation;uinst,G Instantaneous deformation for permanent actionuinst,Q Instantaneous deformation for variable actionx Distance from the line of action of the support reaction to

the corner of the notch

Greek letters

a Angle of stress or load to grainan Ratio of effective member depth to member depth in

notched beamsb Ratio of pointside-to-headside embedment strengthsbc Material constant for evaluation of lateral buckling

modification factorcF Partial factor for the actioncG Partial safety factor for permanent actionscM Partial factor for a material propertycQ Partial safety factor for variable actionskrel,m Relative slenderness under bendingkrel,y Relative slenderness ratio corresponding to bending about

the y-axiskrel,z Relative slenderness ratio corresponding to bending about

the z-axisky Slenderness ratio corresponding to bending about the y-axiskz Slenderness ratio corresponding to bending about the z-axisn Material constant for evaluation of lateral torsional buckling

modification factorqk Characteristic density of the wood-based material




9

Source reference

qm Mean density of timber or wood-based materialrc,0,d Design compressive stress parallel to grainrc,90,d Design compressive stress in the effective contact area

perpendicular to grainrc,α,d Design compressive stress at an angle α to grainrm,y,d Design bending stress about the (strong) y-axisrm,z,d Design bending stress about the (weak) z-axisrt,0,d Design tensile stress parallel to grainrt,90,d Design tensile stress perpendicular to the grain at the

hole locationsd Design shear stressstor,d Design torsional stressw0 Factor for combination value of a variable actionw1 Factor for frequent value of a variable actionw2 Factor for quasi-permanent value of a variable action


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Concise Eurocodes: Design of Timber Structures€¦ · · 2012-10-19Concise Eurocodes: Design of Timber Structures: ... Concise Eurocodes: Design of Timber Structures BS EN 1995: