Designers' Guide to Eurocode 4 - Design of Composite Steel and Concrete Structures EN 1994-1-1 (2nd Edition)

245 Pages·2012·3.955 MB·245\245

by  Johnson, Roger P.

DESIGNERS’ GUIDES TO THE EUROCODES
DESIGNERS’ GUIDE TO EUROCODE 4:
DESIGN OF COMPOSITE STEEL AND
CONCRETE STRUCTURES
EN 1994-1-1
Second edition
ROGER P. JOHNSON
University of Warwick, UK
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Designers’GuidetoEurocode4:Designofcompositesteelandconcretestructures
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Introduction
TheprovisionsofEN1994-1-1(BritishStandardsInstitution,2004a)areprecededbyaforeword,
most of whichis common toall Eurocodes. The Foreword containsclauses on:
g thebackground to theEurocodeprogramme
g thestatusand fieldof application of the Eurocodes
g nationalstandards implementing Eurocodes
g links betweenEurocodesand harmonised technical specifications forproducts
g additionalinformation specific toEN 1994-1-1
g theNationalAnnexfor EN 1994-1-1.
GuidanceonthecommontextisprovidedintheintroductiontotheDesigners’GuidetoEN1990,
Eurocode:BasisofStructuralDesign(Gulvanessianetal.,2002),andonlybackgroundinforma-
tion essential to users ofEN 1994-1-1is given here.
EN 1990 (British Standards Institution, 2005a) lists the followingstructural Eurocodes:
EN 1990 Eurocode:Basisofstructural design
EN 1991 Eurocode 1:Actionson structures
EN 1992 Eurocode 2:Designof concrete structures
EN 1993 Eurocode 3:Designof steel structures
EN 1994 Eurocode 4:Designof composite steel and concrete structures
EN 1995 Eurocode 5:Designof timberstructures
EN 1996 Eurocode 6:Designof masonry structures
EN 1997 Eurocode 7:Geotechnical design
EN 1998 Eurocode 8:Designof structures for earthquake resistance
EN 1999 Eurocode 9:Designof aluminium structures
Thetencodeshave58parts,allofwhichhavebeenpublishedintheUKbytheBritishStandards
Institution (BSI) as, forexample,BS EN 1994-1-1.
The information specific to EN 1994-1-1 emphasises that this standard is to be used with
otherEurocodes.Thestandardincludesmanycross-referencestoparticularclausesinEN1992
(British Standards Institution, 2004b) and EN 1993 (British Standards Institution, 2005b).
Similarly,thisguideisoneofaseriesonEurocodes,andisforusewiththeguideforEN1992-
1-1(BeebyandNarayanan,2005)andtheguideforEN1993-1-1(GardnerandNethercot,2007).
Where, in a building, types of loading or structural member occur that are typical
of bridges, EN 1994-2 (British Standards Institution, 2005c) is relevant, and the guide to
EN 1994-2,‘Compositebridges’(Hendy and Johnson, 2006), maybe useful.
Each national standards body has implemented each Eurocode part as a national standard. It
comprises, without any alterations, the full text of the Eurocode and its annexes as published
by the European Committee for Standardization (CEN), usually preceded by a National Title
Pageanda NationalForeword,and followed by a NationalAnnex.
EachEurocoderecognisestherightofnationalregulatoryauthoritiestodeterminevaluesrelated
to safety matters. Values, classes or methods to be chosen or determined at national level are
referred to as Nationally Determined Parameters (NDPs). A recommended value for each one
1
Designers’GuidetoEurocode4:Designofcompositesteelandconcretestructures
is given in a note that follows the relevant clause. These clauses are listed in the Foreword. The
values are usuallythoseassumed during drafting and used for calibration work.
In EN 1994-1-1 the NDPs are principally the partial factors for material or product properties
peculiar to this standard; for example, for the resistance of headed stud shear connectors, and
of composite slabs to longitudinal shear. Other NDPs are values that may depend on climate,
such asthe free shrinkage of concrete.
EachNationalAnnexgivesorcross-referstothevaluestobeusedfortheNDPsinitscountry.All
butoneofthe12recommendedvaluesofNDPsinEN1994-1-1havebeenacceptedforuseinthe
UK,twowithqualification.Theexceptionisinclause9.6(2),onthedeflectionofprofiledsheeting.
Otherwise,theNationalAnnexmaycontainonlythefollowing(EuropeanCommission,2002):
g decisions on the application of informativeannexes
g references tonon-contradictory complementary information (NCCI) toassistthe userin
applying the Eurocode.
It will be noted that National Annexes may refer to NCCI, but cannot include it. In practice,
questions on the interpretation of code clauses always arise. Any organisation can publish
materialclaimedtobe‘non-contradictory’,andparticularindustriesmayhaveavestedinterest
in doing so. Two interpretations of a particular provision could appear, such that they cannot
both be non-contradictory.
Each National Annex will have been approved by the relevant national standards body (BSI
for the UK), which in effect gives NCCI to which it refers a status close to that of a national
standard. However, much NCCI will appear after the National Annex has been published.
Before using such material for work claimed to be in accordance with Eurocodes, the designer
should be satisfied that it isnon-contradictory.
Drafting errors in codes and some questions of interpretation are resolved by the official
corrigenda and amendments that appear during the lifetime of a code. Proposals for these are
classified as ‘editorial’ or ‘technical’. As they would apply in all EU member states, technical
changes have to be approved by CEN Committee TC250/SC4. A list of editorial corrigenda to
EN 1994-1-1 was issued by the BSI in April 2008. The important ones are mentioned in this
guide. So far, (2011) there have beenno technical changes to EN 1994-1-1.
REFERENCES
Beeby AW and Narayanan RS (2005) Designers’ Guide to EN 1992-1-1. Eurocode 2: Design of
Concrete Structures (Common Rules for Buildings and Civil Engineering Structures). Thomas
Telford,London.
BritishStandardsInstitution(BSI)(2004a)BSEN1994-1-1.Designofcompositesteelandconcrete
structures.Part1-1:Generalrulesandrulesforbuildings.BSI,London.
BSI (2004b) BS EN 1992-1-1. Design of concrete structures. Part 1-1: General rules and rules for
buildings.BSI,London.
BSI(2005a)BSEN1990þA1.Eurocode:basisofstructuraldesign.BSI,London.
BSI (2005b) BS EN 1993-1-1. Design of steel structures. Part 1-1: General rules and rules for
buildings.BSI,London.
BSI (2005c) Design of composite steel and concrete structures. Part 2: Bridges. BSI, London,
BSEN1994-2.
European Commission (2002) Guidance Paper L (Concerning the Construction Products Directive –
89/106/EEC).ApplicationandUseofEurocodes.EC,Brussels.
Gardner L and Nethercot D (2007) Designers’ Guide to EN 1993-1-1. Eurocode 3: Design of Steel
Structures(GeneralRulesandRulesforBuildings).ThomasTelford,London.
Gulvanessian H, Calgaro JA and Holicky´ M (2002) Designers’ Guide to EN 1990. Eurocode: Basis
ofStructuralDesign.ThomasTelford,London.
Hendy CR and Johnson RP (2006) Designers’ Guide to EN 1994-2. Eurocode 4: Design of
Composite Steel and Concrete Structures. Part 2: General Rules and Rules for Bridges. Thomas
Telford,London.
2
Preface to the first edition
EN 1994, also known as Eurocode 4, is one standard of the Eurocode suite and describes the
principles and requirements for safety, serviceability and durability of composite steel and
concrete structures. Itissubdivided into three parts:
g Part1-1: ‘General rules and rules forbuildings’
g Part 1-2: ‘Structural fire design’
g Part 2: ‘Bridges’.
It is intended to be used in conjunction with EN 1990 (‘Basis of structural design’), EN 1991
(‘Actions on structures’) and the other design Eurocodes.
Aims and objectives of this guide
Theprincipalaimofthisbookistoprovidetheuserwithguidanceontheinterpretationanduse
of EN 1994-1-1 and to present worked examples. The guide explains the relationship with the
otherEurocodepartstowhichitrefersandwiththerelevantBritishcodes.Italsoprovidesback-
ground information and references toenable users of Eurocode 4 to understand the origin and
objectives of its provisions.
Layout of this guide
EN 1994-1-1 has a foreword and nine sections, together with three annexes. This guide has an
introduction that corresponds to the foreword of EN 1994-1-1, and Chapters 1 to 9 of the
guidecorrespondtoSections1to9oftheEurocode.Chapters10and11correspondtoAnnexes
AandBoftheEurocode,respectively.AppendicesAtoDofthisguideincludeusefulmaterial
from the draft Eurocode ENV 1994-1-1.
Thenumberingandtitlesofthesectionsinthisguidealsocorrespondtothoseoftheclausesof
EN 1994-1-1.Somesubsectionsarealsonumbered(e.g.1.1.2).Thisimpliescorrespondencewith
thesubclauseinEN 1994-1-1ofthesamenumber.Theirtitlesalsocorrespond.Thereareexten-
sive references tolower-level clauseandparagraphnumbers.The firstsignificantreferenceisin
bolditalictype(e.g.clause1.1.1(2)).Theseareinstrictnumericalsequencethroughoutthebook,
tohelpreaderstofindcommentonparticularprovisionsofthecode.Somecommentsonclauses
are necessarily out ofsequence,but use ofthe index should enable these to be found.
All cross-references in this guide to sections, clauses, subclauses, paragraphs, annexes, figures,
tables and expressions of EN 1994-1-1 are in italic type, which is also used where text from a
clause inEN 1994-1-1 hasbeen directly reproduced (conversely, cross-references to and quota-
tions from other sources, including other Eurocodes, are in roman type). Expressions repeated
from EN 1994-1-1 retain their number; other expressions have numbers prefixed by D (for
Designers’ Guide); e.g. Equation D6.1 inChapter 6.
Acknowledgements
TheauthorsaredeeplyindebtedtotheothermembersofthefourprojectteamsforEurocode4
on which they have worked: Jean-Marie Aribert, Gerhard Hanswille, Bernt Johansson, Basil
Kolias, Jean-Paul Lebet, Henri Mathieu, Michel Mele, Joel Raoul, Karl-Heinz Roik and Jan
Stark;andalsototheLiaisonEngineers,NationalTechnicalContacts,andotherswhoprepared
nationalcomments.TheythanktheUniversityofWarwickforfacilitiesprovidedforEurocode
work, and,especially, their wives Diana and Linda fortheir unfailing support.
R.P. Johnson
D. Anderson
v
Contents
Preface tothe first edition v
Aims and objectives ofthis guide v
Layout ofthis guide v
Acknowledgements v
Preface tothe second edition vi
Introduction 1
References 2
Chapter 1 General 3
1.1. Scope 3
1.2. Normative references 5
1.3. Assumptions 6
1.4. Distinction between principles and application rules 6
1.5. Definitions 6
1.6. Symbols 7
References 7
Chapter 2 Basis of design 9
2.1. Requirements 9
2.2. Principles of limit states design 9
2.3. Basic variables 9
2.4. Verification bythe partialfactormethod 9
References 11
Chapter 3 Materials 13
3.1. Concrete 13
3.2. Reinforcing steel 15
3.3. Structural steel 15
3.4. Connectingdevices 16
3.5. Profiled steel sheetingfor compositeslabs inbuildings 17
References 17
Chapter 4 Durability 19
4.1. General 19
4.2. Profiled steel sheetingfor compositeslabs inbuildings 19
Chapter 5 Structural analysis 21
5.1. Structural modellingfor analysis 21
5.2. Structural stability 22
5.3. Imperfections 26
5.4. Calculationof action effects 27
Example 5.1: effectivewidthof a concrete flange 29
5.5. Classification of cross-sections 38
References 41
Chapter 6 Ultimate limit states 43
6.1. Beams 43
6.2. Resistancesof cross-sections ofbeams 46
Example 6.1: resistance moment in hogging bending, with an effectiveweb 54
Example 6.2: resistance tobending and vertical shear 59
vii
6.3. Resistance of cross-sections ofbeams forbuildings with partial
encasement 60
6.4. Lateral–torsional buckling of compositebeams 61
Example 6.3: lateral–torsional buckling ofa two-span beam 70
6.5. Transverse forces on webs 70
6.6. Shearconnection 71
Example 6.4: arrangementof shear connectors 75
Example 6.5: reduction factorsfor transversesheeting 83
Example 6.6: transverse reinforcement forlongitudinal shear 89
Example 6.7: two-span beamwithcomposite slab – ultimate limit state 92
Example 6.8: partial shear connection with non-ductile connectors 110
Example 6.9: elasticresistance to bending, and influence of thedegreeof
shear connection and the type ofconnector on bending resistance 111
6.7. Compositecolumns and composite compression members 113
Example 6.10: compositecolumn with bending aboutone or both axes 123
Example 6.11: longitudinal shear outside areas ofload introduction, for a
composite column 128
6.8. Fatigue 129
Example 6.12: fatigue inreinforcement andshearconnection 135
References 137
Chapter 7 Serviceability limit states 143
7.1. General 143
7.2. Stresses 144
7.3. Deformationsin buildings 144
7.4. Cracking ofconcrete 148
Example 7.1: two-span beam(continued) – SLS 153
References 157
Chapter 8 Composite joints in frames forbuildings 159
8.1. Scope 159
8.2. Analysis, includingmodelling and classification 160
8.3. Design methods 163
8.4. Resistance of components 164
Example 8.1: end-plate joints in atwo-spanbeamin a braced frame 166
References 179
Chapter 9 Composite slabs with profiled steel sheetingforbuildings 181
9.1. General 181
9.2. Detailing provisions 182
9.3. Actionsand action effects 183
9.4. Analysis for internal forces and moments 184
9.5–
9.6. Verification of profiled steel sheetingas shuttering 185
9.7. Verification of compositeslabs forthe ultimatelimit states 185
9.8. Verification of compositeslabs forserviceability limit states 191
Example 9.1: two-span continuous compositeslab 193
References 201
Chapter 10 Annex A(Informative). Stiffnessof jointcomponents inbuildings 203
A.1. Scope 203
A.2. Stiffness coefficients 203
A.3. Deformationof the shear connection 205
Example 10.1: elasticstiffnessof an end-plate joint 205
References 209
Chapter 11 Annex B(Informative). Standardtests 211
B.1. General 211
B.2. Testson shear connectors 212
viii
B.3. Testing of compositefloor slabs 215
Example 11.1: m–ktests on compositefloor slabs 219
Example 11.2: thepartial-interaction method 223
References 226
AppendixA Lateral–torsionalbucklingof composite beams forbuildings 229
Simplified expression for‘cracked’ flexural stiffness ofa composite slab 229
Flexural stiffness ofa beam with encased web 230
Maximumspacing of shear connectors for continuousU-frame action 230
Toptransverse reinforcement above an edge beam 231
Derivation ofthe simplified expression for(cid:1)(cid:1)(cid:1) (Equation D6.14) 232
LT
Effect ofweb encasement on (cid:1)(cid:1)(cid:1) 233
LT
Factor C forthe distribution ofbending moment 233
4
Criteria forthe verification of lateral–torsionalstabilitywithoutdirect
calculation 234
Reference 235
AppendixB The effect ofslab thickness onthe resistance ofcomposite slabs to
longitudinalshear 237
Summary 237
The model 237
The m–kmethod 238
The partial-connection method 240
Reference 241
AppendixC Simplified calculationmethod fortheinteraction curve fortheresistanceof
compositecolumn cross-sections tocompressionand uniaxialbending 243
Scope and method 243
Neutral axesand plastic section moduli of some cross-sections 245
Concrete-filled rectangular and circular hollow sections 247
Example C.1: N–M interaction polygon for acolumn cross-section 247
AppendixD Compositebeams using precastconcreteslabs 251
References 251
Index 253
ix
Designers’GuidetoEurocode4:Designofcompositesteelandconcretestructures
ISBN978-0-7277-4173-8
ICEPublishing:Allrightsreserved
http://dx.doi.org/10.1680/dcscb.41738.003
Chapter 1
General
ThischapterisconcernedwiththegeneralaspectsofBSEN1994-1-1:2004,‘Eurocode4:Design
of composite steel and concrete structures, Part 1-1: General rules and rules for buildings’. It
will be referred to as ‘EN 1994-1-1’. A corrigendum was circulated by the British Standards
Institution (BSI) in April 2008. The few significant changes will be referred to where they are
relevant.ThematerialdescribedinthischapteriscoveredinSection1,inthefollowingclauses:
g Scope Clause1.1
g Normative references Clause1.2
g Assumptions Clause1.3
g Distinction between principles and application rules Clause1.4
g Definitions Clause1.5
g Symbols Clause1.6
1.1. Scope
1.1.1 Scope of Eurocode 4
ThescopeofEN1994(allthreeparts)isoutlinedinclause1.1.1.ItistobeusedwithEN1990, Clause1.1.1
‘Eurocode:basisofstructuraldesign’,whichistheheaddocumentoftheEurocodesuite.Clause Clause1.1.1(2)
1.1.1(2)emphasisesthattheEurocodesareconcernedwithstructuralbehaviourandthatother
requirements(e.g.thermalandacoustic insulation) arenot considered.
The basis for verification of safety and serviceability is the partial factor method. EN 1990
recommends values for load factors, and gives various possibilities for combinations of
actions. The values and choice of combinations are given in the National Annex for the
countryin which the structure isto be constructed.
Eurocode4isalsousedinconjunctionwithEN1991,‘Eurocode1:Actionsonstructures’(BSI,
2002)anditsNationalAnnex,todeterminecharacteristicornominalloads.Whenacomposite
structureistobebuiltinaseismic region,accountneedstobetakenofEN1998,‘Eurocode8:
Design ofstructures for earthquake resistance’(BSI,2004).
Structural fire design (EN 1994-1-2) is outsidethe scope of this guide.
TheEurocodesareconcernedwithdesign,notexecution,butminimumstandardsofworkman-
shiparerequiredtoensurethatthedesignassumptionsarevalid.Forthisreason,clause1.1.1(3) Clause1.1.1(3)
lists the European standards for the execution of steel structures and the execution of concrete
structures. The former includes some requirements for composite construction, for example
for thetesting of welded stud shear connectors.
1.1.2 Scope of Part 1-1 of Eurocode 4
EN 1994-1-1 deals with aspects of design that are common to the principal types of composite
structure,buildingsandbridges.ThisresultsfromtheEuropeanCommitteeforStandardization
(CEN)requirementthataprovisionshouldnotappearinmorethanoneENstandard,asthiscan
causeinconsistencywhenonestandardisrevisedbeforeanother.Forexample,ifthesamerules
forresistancetobendingapplyforacompositebeaminabuildingasinabridge(asmostofthem
do), then those rules are ‘General’ and appear in EN 1994-1-1, even where most applications
occurinbridges.Forexample,clause6.8(fatigue)isinPart1-1,withafewadditionalprovisions
in EN 1994-2 (BSI, 2005).
3
Designers’GuidetoEurocode4:Designofcompositesteelandconcretestructures
InEN1994-1-1,allrulesthatareforbuildingsonlyareprecededbyaheadingthatincludesthe
word ‘buildings’, or, if an isolated paragraph, are placed at the end of the relevant clause (e.g.
clauses 5.3.2 and 5.4.2.3(5)).
The coverage in this guide of the ‘general’ clauses of Part 1-1 is relevant to both buildings and
bridges, except where noted otherwise. However, guidance provided by or related to the
worked examples may be relevantonly toapplications inbuildings.
Clause1.1.2(2) Clause1.1.2(2)liststhetitlesofthesectionsofPart1-1.ThoseforSections1–7arethesameasin
the other material-dependent Eurocodes. The contents of Sections 1 and 2 similarly follow an
agreed model.
The provisions ofPart1-1coverthe design ofthe common composite members:
g beams in which a steel section acts compositely with concrete
g composite slabs formed with profiled steel sheeting
g concrete-encased and concrete-filled compositecolumns
g jointsbetween compositebeams and steel or composite columns.
Sections 5 and 8 concern connected members. Section 5, ‘Structural analysis’, is needed
particularly for framed structures. Unbraced frames and sway frames are within its scope. The
provisions include the use of second-order global analysis and prestress by imposed deforma-
tions, and defineimperfections.
The scope of Part 1-1 extends to steel sections that are partially encased. The web of the steel
sectionisencasedbyreinforcedconcrete,andshearconnectionisprovidedbetweentheconcrete
andthesteel.Thisisawell-establishedformofconstruction.Theprimaryreasonforitschoiceis
improved resistance infire.
Fully-encased compositebeams arenot included because:
g no satisfactory model hasbeen found forthe ultimate strength inlongitudinal shear of a
beamwithoutshear connectors
g it is not known towhat extent some design rules (e.g.for moment–shear interaction and
redistribution of moments)are applicable.
A fully encased beam with shear connectors can usually be designed as if partly encased
or uncased, provided that care is taken to prevent premature spalling of encasement in
compression.
Part2,‘Bridges’,includesfurtherprovisionsthatmayonoccasionbeusefulforbuildings,suchas
those on:
g composite plates(wherethe steel member is aflatsteel plate,not a profiled section)
g composite plate girders and box girders
g tapered or non-uniform compositemembers
g structures that areprestressed by tendons.
The omission ofapplication rules foratypeof member orstructure should notprevent its use,
where appropriate. Some omissions are deliberate, to encourage the use of innovative design,
basedonspecialisedliterature,thepropertiesofmaterials,andthefundamentalsofequilibrium
andcompatibility;andfollowingtheprinciplesgivenintherelevantEurocodes.Thisapplies,for
example,to:
g large holes in webs of beams
g types of shear connector otherthan welded studs
g baseplatesbeneath compositecolumns
g shearheadsin reinforced concrete framedstructures (Piel and Hanswille, 2006)
g manyaspects of‘mixed’structures,as used intall buildings.
4