BSI Structural Eurocodes Companion

8/13/2019 BSI Structural Eurocodes Companion

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BSI

StructuralEurocodesCompanion


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Atkins is one of the worlds leadingmulti-discipline design consultancies, providing innovativeand exciting design solutions to clients in the UK and worldwide

www.atkinsglobal.com Woodcote Grove, Ashley Road, Epsom, Surrey KT18 5BW Plan Design Enable

Atkins has been a significantcontributor to the developmentand introduction of Eurocodesand welcomes their

implementation in the UK


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3BSI Structural Eurocodes Companion

Contents

Section 1. Introduction

Foreword 5

Introduction 5

View from the UK Committee Chairman 7

View from the industry 8

Section 2. The Eurocode timeline

Eurocodes publication schedule 11

Key aspects of the Eurocodes 16

Section 3. Focus on Eurocode materials

Eurocode: Basis of structural design 19

Eurocode 1: Actions on structures 21

Eurocode 2: Design of concrete structures 24

Eurocode 3: Design of steel structures 29

Eurocode 4: Design of composite steel and concrete structures 32

Eurocode 5: Design of timber structures 34

Eurocode 6: Design of masonry structures 36

Eurocode 7: Geotechnical design 38

Eurocode 8: Design of structures for earthquake resistance 39

Eurocode 9: Design of aluminium structures 41

Section 4. Business matters: software and risk

Software to the Eurocodes 43

Implementing Eurocodes: the benefits of computer-basedtraining 45

Insurance and the Eurocodes 49

Structural Eurocodes what they say 51

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Section 1

Introduction


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Foreword / Introduction

Welcome to the 2009 BSI Struc-tural Eurocodes Companionprepared in readiness for one of themost significant developments inconstruction standardization.

Structural Eurocodes are seen asleading the way in structural codes.Their flexibility enables adoptionand use not only within Europe,but internationally. This feature hasbeen recognized by several coun-tries outside Europe and they arealready committed to adoptingEurocodes.

The primary objectives of theEurocodes are to:

p provide common design criteriaand methods of meeting neces-sary requirements for mechanicalresistance, stability and resist-ance to fire, including aspects ofdurability and economy;

p provide a common understand-

ing regarding the design ofstructures between owners,operators and users, designers,

contractors and manufacturersof construction products;

p facilitate the marketing and useof structural components andkits in EU Member States;

p facilitate the marketing and useof materials and constituent pro-ducts, the properties of whichenter into design calculations;

p be a common basis for researchand development, in the con-struction industry;

p allow the preparation of com-mon design aids and software;

p increase the competitiveness ofthe European civil engineeringfirms, contractors, designersand product manufacturers intheir global activities.

Each of the Eurocode parts is pro-duced by a subcommittee underthe guidance and coordination of atechnical committee (CEN/TC 250).

Delegates of the 29 Comit Europende Normalisation (CEN) members

are represented on CEN/TC 250and its subcommittees.

Drafts of the Eurocode parts areelaborated by project teams, whichare selected by the appropriate sub-committees. A project team consistsof about six experts who representthe subcommittee. A vast majorityof the project teams include a UK-based expert.

A Eurocode is subject to exten-sive consultation before it isadopted. Progressive drafts are dis-cussed and commented on by CENmembers and their appointedexperts. AEurocode part is adoptedonly after a positive vote by CENMembers.

This BSI Structural EurocodesCompanion contains articles fromleading academics and profession-als to help you gain an understand-ing of the nature of the new codesand to ease your integration into the

new approach being undertaken. p

ForewordProfessor John Roberts, Principal, Technical Innovation Consultancy

The Structural Eurocodes havebeen a feature of virtually thewhole of my professional life. Atmy first technical conference heldin Paris in 1972 I was introduced toseveral individuals, who subse-quently became key figures in thepreparation of a number of thesedocuments; my research, teaching,advisory, professional and BSIactivities have taken place against

the backdrop of the writing of theENV and EN documents and, morerecently, I have been involved withseveral initiatives intended to facil-

itate their introduction andadoption.

In 1976 the UK signed up to theTreaty of Rome. This contained, asone of its essential tenets, theremoval of artificial barriers totrade. The existence of nationalcodes in each of the various mem-ber states for the design of struc-tural works was seen as oneexample of such a barrier. Thus

more than 30 years ago the UKcommitted to the eventual replace-ment of its national standards, pre-pared under the auspices of BSI, by

the Eurocodes, prepared under thegeneral direction of CEN. We havenow reached the stage where thatprospect has become the reality.

The suite of Structural Eurocodeswill contain 58 documents, cover-ing all structural materials includ-ing loading. Collectively theyrepresent the biggest ever changefor our structural engineering com-munity more significant than the

transfer to limit states or the intro-duction of metric units. Shouldthis be seen as a threat or anopportunity?

IntroductionProfessor David Nethercot OBE FREng, Chairman, I Struct E, Standing Committee on the Implementation

of Eurocodes


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BSI Structural Eurocodes Companion6


To adopt an insular, grudgingand ignoring as far as possibleattitude would be to convert theEurocodes into a threat. On theother hand to adopt a pragmatic,positive and how can we benefitattitude sees the change as anopportunity. Of course, new Struc-tural Codes are always unwelcome:

The onset of new or revised regula-tions invariably heralds a tryingperiod of the unfortunate peoplewho have to work such regulations.This applies both to those who haveto comply with, and those who haveto administer, such regulations.

Whilst that quote might be thoughtto be a statement on the Eurocodes,it actually refers to the introductionsome 50 years ago of a revision toBS 449 a document that somewould still regard as a paragon ofall that codes should be. Given thatthe Structural Eurocodes have beenprepared on a collaborative basis,they clearly cannot be expected toreflect the exact requirements of the

UK. However, through substantialinvolvement with the draftingprocess, including chairmanship ofseveral of the main committees, thiscountry has ensured that the docu-ments are far less unfamiliar thanmight otherwise have been thecase. There are rules, agreements onterminology, and structures for thedocuments that do have to be fol-lowed and which, unsurprisingly,do not accord with BSI arrange-ments. However, within this frame-

work, the material is rather lessdifferent than might, at first sight,be thought to be the case.

The UK is now in the midst of aperiod of transferring the basis ofstructural design from an environ-ment based on national standardsto one founded on the StructuralEurocodes. This is a far from trivialtask. It therefore needs to beaccepted by UK industry as a body,by its member organizations and

by individuals, that just like anyengineering project, it requiresplanning, resourcing and effort tomake it successful. For companies itshould be regarded as akin to thepurchase of a new computer sys-tem or the move to new premises.For individuals, it represents animportant facet of operating as aprofessional person, i.e. recogniz-ing that the operating climate willchange over time and accepting theimperative to update skills andcompetences and to work with thenew tools.

1. Accept the reality of the situa-tion: Eurocodes are fact, therewill be no more BritishStandards.

2. Understand the difference be-tween the legal requirements ofBuilding Regulations, HighwaysAgency requirements, etc. andthe use of Structural Codes.

3. Treat migration from a designenvironment based on BritishStandards to one based on theEurocodes as a project.

4. Recognize that the transitionperiod will, in reality, extendover a number of years, withelements of parallel application.

5. Remember that actual methodsof working on structural designsuse a portfolio of aides, e.g.manuals, manufacturers infor-mation, computer software, text-books. Over time Eurocode-based material will replace thefamiliar and reassuring currentBritish Standards-based items; thisprocess is already in place withseveral items available but devel-oping familiarity needs time.

6. Remember that code rules arethere to assist structural design-ers not as a prescriptive recipeapproach, and that structuralengineering knowledge andunderstanding is universal andcan be applied in any designenvironment.

7. Remain sanguine and take a bal-anced view be particularlycautious when reading claims ofwhat must be done; the climatewithin which structural engi-

neering is practiced in the UK isfar less prescriptive than somewould have us believe.

8. Take courage from the exampleof those silver surfers whohave found new opportunitiesin the internet; Eurocodes arenot about old dogs learning newtricks, they are about dogs of allages performing much the sameset of tricks but with a new andimproved set of equipment. p

Through substantialinvolvement with thedrafting process, includingchairmanship of severalof the main committees,the UK has ensured thatthe documents are far lessunfamiliar than mightotherwise have been the

case.

The suite of Structural Eurocodesrepresent:

p the most advanced technicalviews prepared by the bestinformed groups of experts intheir fields across Europe;

p the most comprehensive treat-

ment of the subjects, with manyaspects not previously codifiednow being covered by agreedprocedures;

p a design framework plus detailedimplementation rules validacross Europe and likely to findsignificant usage worldwide.

What therefore should the struc-tural engineering community do?

Some suggestions:


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Iam pleased to be able to write anarticle for this important publica-tion. The Eurocodes are a signifi-cant technical achievement as wellas enabling real progress in theopening of the construction marketin Europe.

The process was long and it isimportant to understand somethingof how the Eurocodes were writtenbefore a full understanding andappreciation can be gained. The reg-ulation and codification of construc-tion has a long history, the firstBuilding Regulations in the UKwere issued shortly after the GreatFire of London. Design codes as weunderstand them were introducedin the beginning of the 20th centuryand were based on an understand-ing of the underlying engineeringscience current at the time.

The approach relied upon theproportionality between load anddisplacement of elastic materialsrecorded by Hooke. In the mid-20thcentury, a new approach was intro-duced that relied upon the propertyof yield and plastic flow of elastic-plastic materials. The two theoriesallowed design rules to be writtenthat were able to control service per-formance (the Elastic theory) andgive accurate collapse and safety

predictions (the Plastic theory). Thisnew process called limit statedesign was capable of following theperformance of a structure from itsworking load to an accurate predic-tion of collapse. Limit state designwas first applied in the UK in thecode for the design of concretestructures, CP110 in 1972, and theapplication to steel and masonrydesign soon followed.

The limit state design conceptwas developed by various inter-

national groups, although one ofwhich, the Euro InternationalCommittee for Concrete (CEB), wasparticularly active. In 1964 recom-

mendations for an internationalcode of practice were publishedwhich were based on CEB andUnited States joint activities. Theintroduction to this publicationmentions the aspiration for a Euro-pean code of practice. It was thiswork that led to CP110 in 1972.

By 1980, the European Commis-sion had a requirement for Euro-pean design standards to fulfil itsobjectives of an open market forconstruction, construction productsand for construction design serv-ices and turned to the work thatwas already being carried out by

progressed the work and will con-tinue to be responsible, now thatthe Eurocodes have all been pub-lished, for further development,including the maintenance andrevision cycles.

That the work took nearly 50years from a point when the con-cept of the process was establishedand 30 from the time that it becamepolitically necessary seems disap-pointing, but there were very manygreat difficulties that the draftersand officials had to overcome.

European engineering and con-struction cultures are varied, somecountries have a practical approachand in others the approach is moremathematical and academic. Theposition of design codes in thelegal framework in the variousmember states is very different.

In some states codes are seen asdeemed to satisfy documentswhich are referred to in brief nat-ional regulations, in others, codesare written into the countries legalcode.

Europe has undergone two peri-ods of enlargement while the workwas being carried out, necessitatingthe consideration of new input. Thetime taken for the work to come tocompletion has meant that more

than one generation of engineershas passed through the committees.The time has also allowed ideasfrom new research and practicalexperience to be incorporated

Although we still have to over-come the problem posed by thecontrol of safety being the preroga-tive of the individual memberstates, which has brought about therequirement for national annexes,the 58 separate documents in theEurocode suite are all identical in

each member state.I believe that this final achieve-

ment is remarkable. p


View from the UK Committee Chairman

View from the UK Committee ChairmanHoward P. J. Taylor FREng, Chair BSI Committee B525, Structural Design Codes (Mirror Committee to

CEN TC 250)

the then extensive network of vol-untary practicing engineers and

academics. Funding was providedfor a period but by 1988 it was clearthat a more structured approachwas required and the Commissionturned to CEN, the existing organi-zation that coordinated standardswork throughout Europe, andcharged it with the final productionof the Eurocodes. BSI as the UKnational standards body is a mem-ber of CEN.

CEN gave the responsibility ofthe Eurocode work to one of its

many committees working onEuropean standards, CommitteeTC 250. From that time, TC 250with its many subcommittees has

European engineeringand construction cultures

are varied, some countrieshave a practical approachand in others the approachis more mathematical andacademic.


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The Eurocodes are widelyregarded as the most techni-cally advanced suite of structuraldesign codes available internation-ally. Why then is it often perceivedthat progress towards their adop-tion has been slow in the UK?

There is undoubtedly still someresistance from pockets of the UKstructural community. Part of theinertia comes from the fact that theUK has extremely good BritishStandards already. For example,BS 5400 Part 3 is widely consideredto be the most comprehensive steelcode of practice in the world butfew would describe it as the mosteconomic. Some in the UK argue thatthe Eurocode rules go too far andare, in some isolated cases, unsafe.There is, however, no evidence ofthis, particularly when the UKNational Annex has, in a few places,

tightened up requirements wherethe Eurocode has permitted this tobe done. Arguments that theEurocodes are unsafe because theygive different answers to previousBritish codes are simply unsoundand in places the British Standardsare far too conservative and areincreasingly being shown to be so.

Other resistance stems from theperceived effort involved in thechangeover. The Eurocode aware-

ness seminars that have been heldover the last few years may poten-tially have been counter productive.They have been intended to reas-sure, whilst at the same time demon-strate there is work to do. In somecases, pointing out a long list of dif-ferences in practice has made theprocess of adoption appear moredaunting than perhaps it really is.

While there may be some resist-ance from within industry, BSI andthe Highways Agency are actively

driving implementation. The pro-duction of national annexes is pro-ceeding at a pace and will besubstantially complete by January

2009, which is on a par with or bet-ter than the progress made bymuch of mainland Europe; bridgedesign should be fully enabled inthe UK by that date. In addition, anincreasing number of consultantsare using Eurocodes to form thebasis of departures from standardsin the assessment of existing struc-tures because they can improvepredicted load carrying resistance.

The state of readiness of industrybodies, software houses and institu-tions is also excellent by comparisonwith our other European counter-parts. The Concrete Centre andSteel Construction Institute have

series of four-day training coursesto 60 Champions across the UKand ensured that all other staff havereceived a lower level of awarenesstraining whilst being given accessto the detailed training material.Other companies are planning sim-ilar strategies. However, a signifi-cant number of companies are onlyjust starting to consider the issue.

Designers who are not preparedface a risky transition period. Theintroduction of Eurocodes will pro-vide a common set of design codesfor use across Europe and, as con-sidered below, in a number of coun-tries outside Europe. Apart from aunique national annex (which canprovide very limited informationand will thus be very easy to assim-ilate by foreign competitors), adesign done in the UK will followthe same set of rules as one done

elsewhere in Europe. This will facil-itate competition by UK designersacross a wide range of countriesbut, of course, the reverse will alsobe true. If we are slow to adapt inthe UK, others will not be and thisbrings potential threats to ourindustry.

The threats will not only comefrom within Europe. Countrieswith an existing reliance on, orclose link to, British Standards are

either already committed to adopt-ing Eurocodes (e.g. Malaysia andSingapore) or are weighing up thebenefits of adopting them (e.g.Hong Kong). In addition, trainingis starting in these countries. Forexample, the Institution of Engi-neers Malaysia commissionedAtkins to run a two-day Eurocodeconcrete bridge design trainingcourse for 85 delegates in KualaLumpur in September 2007, thencommissioned another for steel

design in March 2008, and two fur-ther courses ran in East Malaysia inJuly 2008. There is no similar-scaleexternal training taking place in the

View from the industryChris Hendy, Atkins plc

In places British Stan-dards are far too conserva-tive and are increasinglybeing shown to be so If we are slow to adapt inthe UK, others will not beand this brings potentialthreats to our industry.

produced, and continue to produce,much guidance and training mate-rial. Many of the big softwarehouses are on top of softwareupgrades, waiting only for finalnational annexes to finalizereleases. The ICE and IStructE arerunning seminars and training andpublishing a comprehensive set ofdesigners guides to the variousEurocode parts.

Readiness amongst designers is,however, more patchy. Some of the

big consultants have strategies inhand for helping their engineers tomake the transition. Atkins, forexample has already rolled out a


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Eurocodes - benefits, threats and UK plcs state of readiness

UK in bridge design. These coun-tries may take a keen interest in UKopportunities.

The introduction of Eurocodesand the increased technical sophis-tication they bring is timely giventhe growing importance of the sus-tainability agenda and the drivefor leaner construction. Many ofthe basic application rules in theEurocodes lead to a modest butsignificant improvement in econ-omy compared to existing BritishStandards. In many cases, this isderived from more recent research

and testing. However, designersthat follow the more complex meth-ods of analysis permitted by the highlevel principles, such as non-linear

analysis, may find very consider-able improvements in economy.This will be the case, for example,for slender concrete piers or slendersteel panels.

So to return to the original ques-tion, we shouldnt consider thatthe performance of UK plc hasbeen sluggish. We should how-ever recognize that the Eurocodesbring both opportunities andthreats, and so to maximize the for-mer and mitigate the latter now isthe time to step up our preparationactivities. p

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Section 2

The Eurocodetimeline


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Eurocodes publication schedule

Eurocode. BS EN 1990 Basis of structural design

Eurocode part Title UK National Annex

publication status

BS EN 1990:2002 Basis of structural design Published

BS EN 1990:2002 Basis of structural design including Amendment A1Annex A2 for Annex A2 for Bridges Expected 2009

Eurocode 1. BS EN 1991 Actions on structures

Eurocode part Title UK National Annexpublication status

BS EN 1991-1-1:2002 Actions on structures. General actions. Densities, Publishedself-weight, imposed loads for buildings

BS EN 1991-1-2:2002 Actions on structures. General actions. Actions on Publishedstructures exposed to fire

BS EN 1991-1-3:2003 Actions on structures. General actions. Snow loads Published

BS EN 1991-1-4:2005 Actions on structures. General actions. Wind actions Published

BS EN 1991-1-5:2003 Actions on structures. General actions. Thermal Publishedactions

BS EN 1991-1-6:2005 Actions on structures. General actions. Actions Publishedduring execution

BS EN 1991-1-7:2006 Actions on structures. General actions. Accidental Publishedactions

BS EN 1991-2:2003 Actions on structures. Traffic loads on bridges Published

BS EN 1991-3:2006 Actions on structures. Actions induced by cranes Expected 2009

and machinery

BS EN 1991-4:2006 Actions on structures. Silos and tanks Expected 2009

The following tables show the publication dates for the Eurocodes and the corresponding UKNational Annexes.

*This schedule is correct at the time of going to print. For the very latest information please go towww.bsigroup.com/eurocodes.*



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PD 6688-1-1 Proposed title: Background paper to the UK Expected 2009National Annex to BS EN 1991-1-1

PD 6688-1-2:2007 Background paper to the UK National Annex to Published

BS EN 1991-1-2

PD 6688-1-4 Proposed title: Background paper to the UK National Expected 2009Annex to BS EN 1991-1-4

PD 6688-1-5 Proposed title: Background paper to the UK National Expected 2009Annex to BS EN 1991-1-5

PD 6688-1-7 Recommendations for the design of structures to PublishedBS EN 1991-1-7

PD 6688-2 Recommendations for the design of structures to Expected 2009

BS EN 1992-2

Eurocode 2. BS EN 1992 Design of concrete structures


BS EN 1992-1-1:2004 Design of concrete structures. General rules and rules Publishedfor buildings Amd 1 in prepara-

tion, expected 2009

BS EN 1992-1-2:2004 Design of concrete structures. Fire design Published

BS EN 1992-2:2005 Design of concrete structures. Concrete bridges. Design Publishedand detailing rules

BS EN 1992-3:2006 Design of concrete structures. Liquid retaining and Publishedcontaining structures

PD 6687:2006 Background paper to the UK National Annexes to PublishedBS EN 1992-1

PD 6687-1 Background paper to the UK National Annexes to PublishedBS EN 1992-1 and BS EN 1992-3 (supersedesPD 6687:2006)

PD 6687-2:2007 Recommendations for the design of structures to PublishedBS EN 1992-2




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Eurocode 3. BS EN 1993 Design of steel structures


BS EN 1993-1-1:2005 Design of steel structures. General rules and rules for Publishedbuildings

BS EN 1993-1-2:2005 Design of steel structures. General rules. Structural fire Publisheddesign

BS EN 1993-1-3:2006 Design of steel structures. General rules. Supplementary Expected 2009rules for cold-formed members and sheeting

BS EN 1993-1-4:2006 Design of steel structures. General rules. Supplementary Expected 2009rules for stainless steels

BS EN 1993-1-5:2006 Design of steel structures. Plated structural elements Published

BS EN 1993-1-6:2007 Design of steel structures. General. Strength and Expected 2009stability of shell structures

BS EN 1993-1-7:2007 Design of steel structures. General. Plated structures Expected 2009subject to out of plane loading

BS EN 1993-1-8:2005 Design of steel structures. Design of joints Published

BS EN 1993-1-9:2005 Design of steel structures. Fatigue strength Published

BS EN 1993-1-10:2005 Design of steel structures. Material toughness and Publishedthrough-thickness properties

BS EN 1993-1-11:2006 Design of steel structures. Design of structures with Publishedtension components

BS EN 1993-1-12:2007 Design of steel structures. Additional rules for the Publishedextension of EN 1993 up to steel grades S 700

BS EN 1993-2:2006 Design of steel structures. Steel bridges Published

BS EN 1993-3-1:2007 Design of steel structures. Towers, masts and Expected 2009chimneys. Towers and masts

BS EN 1993-3-2:2008 Design of steel structures. Towers, masts and Expected 2009chimneys. Chimneys

BS EN 1993-4-1:2007 Design of steel structures. Silos, tanks and pipelines. Expected 2009Silos

BS EN 1993-4-2:2007 Design of steel structures. Silos, tanks and pipelines. Expected 2009Tanks

BS EN 1993-4-3:2007 Design of steel structures. Silos, tanks and pipelines. Expected 2009Pipelines

BS EN 1993-5:2007 Design of steel structures. Piling Expected 2009

BS EN 1993-6:2007 Design of steel structures. Crane supporting structures Expected 2009


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PD 6695-1-9 Proposed title: TBA Published

PD 6695-1-10 Proposed title: TBA Published

PD 6695-2 Proposed title: Recommendations for the design of Publishedstructures to BS EN 1993-2:2006

Eurocode 4. BS EN 1994 Design of composite steel and concrete structures


BS EN 1994-1-1:2004 Design of composite steel and concrete structures. Published

General rules and rules for buildings

BS EN 1994-1-2:2005 Design of composite steel and concrete structures. PublishedGeneral rules. Structural fire design

BS EN 1994-2:2005 Design of composite steel and concrete structures. PublishedGeneral rules and rules for bridges

PD 6696-2:2007 Recommendations for the design of structures to PublishedBS EN 1994-2:2005

Eurocode 5. BS EN 1995 Design of timber structures


BS EN 1995-1-1:2004 Design of timber structures. General. Common rules Publishedand rules for buildings

BS EN 1995-1-2:2004 Design of timber structures. General. Structural fire Publisheddesign

BS EN 1995-2:2004 Design of timber structures. Bridges Published

Eurocode 6. BS EN 1996 Design of masonry structures


BS EN 1996-1-1:2005 Design of masonry structures. General rules for Publishedreinforced and unreinforced masonry structures

BS EN 1996-1-2:2005 Design of masonry structures. General rules. PublishedStructural fire design




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BS EN 1996-2:2006 Design of masonry structures. Design considerations, Publishedselection of materials and execution of masonry

BS EN 1996-3:2006 Design of masonry structures. Simplified calculation Published

methods for unreinforced masonry structures

Eurocode 7. BS EN 1997 Geotechnical design


BS EN 1997-1:2004 Geotechnical design. General rules Published

BS EN 1997-2:2007 Geotechnical design. Ground investigation and testing Expected 2009

PD 6694-1:2007 Proposed title: Recommendations for the design of Expected 2009structures subject to traffic loading to BS EN 1997-1:2004

Eurocode 8. BS EN 1998 Design of structures for earthquake resistance


BS EN 1998-1:2004 Design of structures for earthquake resistance. PublishedGeneral rules, seismic actions and rules for buildings

BS EN 1998-2:2005 Design of structures for earthquake resistance. Bridges Expected 2009

BS EN 1998-3:2005 Design of structures for earthquake resistance. No NA to beAssessment and retrofitting of buildings published

BS EN 1998-4:2006 Design of structures for earthquake resistance. Silos, Publishedtanks and pipelines

BS EN 1998-5:2004 Design of structures for earthquake resistance. PublishedFoundations, retaining structure and geotechnicalaspects

BS EN 1998-6:2005 Design of structures for earthquake resistance. Towers, Publishedmasts and chimneys

PD 6698:2009 Background paper to the UK National Annexes to Expected 2009BS EN 1998-1, BS EN 1998-2, BS EN 1998-4,BS EN 1998-5 and BS EN 1998-6


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p The Eurocodes support NationalBuilding Regulations and othernational requirements for regu-lated work but remain sub-servient to them.

p National regulations set the ap-propriate level of safety throughNationally Determined Para-meters (NDP). Certain otherparameters can be set by indi-vidual countries.

p The clauses in the Eurocodes aredivided into principles andapplication rules. Principles areidentified by (P) after the clausenumber and cover items forwhich no alternative is permit-

ted. Application rules are recom-mended methods of achievingthe principles but alternativerules may also be used.

p There are two types of annex inthe Eurocodes. Normative an-nexes are part of the require-ments of the code.

p Informative annexes provideguidance that can be adoptedor not on a country by countrybasis.

p The national annex is a specialtype of informative annex thatcontains the choices made by aparticular country. Typically

the national annex will statevalues and classes applicable tothat country, provide valuewhere only a symbol is given inthe Eurocode and providecountry specific data. Thenational annex also chooseswhen alternatives are given inthe Eurocodes and indicateswhich informative annexesmay be used. Finally it refers tonon-contradictory complemen-tary information (NCCI).

p An NCCI is a way of introduc-ing additional guidance to sup-plement the Eurocodes withoutcontradicting them. p



Eurocode 9. BS EN 1999 Design of aluminium structures


BS EN 1999-1-1:2007 Design of aluminium structures. General structural rules Published

BS EN 1999-1-2:2007 Design of aluminium structures. Structural fire design Published

BS EN 1999-1-3:2007 Design of aluminium structures. Structures susceptible Publishedto fatigue

BS EN 1999-1-4:2007 Design of aluminium structures. Cold-formed structural Publishedsheeting

BS EN 1999-1-5:2007 Design of aluminium structures. Shell structures Published

Key aspects of the Eurocodes


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Section 3

Focus on Eurocodematerials


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BS EN 1990, Eurocode: Basis ofstructural design, is the head keycode for the harmonized StructuralEurocodes. BS EN 1990 establishesfor all the Structural Eurocodes theprinciples and requirements forsafety and serviceability and pro-vides the basis and general princi-ples for the structural design andverification of buildings and civilengineering structures (includingbridges, towers and masts, silos andtanks, etc.). BS EN 1990 gives guide-lines for related aspects of structuralreliability, durability and qualitycontrol. It is based on the limit stateconcept and used in conjunctionwith the partial factor method.

As shown in the figure,BS EN 1990 will be used with everyEurocode part for the design of newstructures, together with:

p BS EN 1991 Eurocode 1:Actionson structures; and

p the design Eurocodes BS EN 1992to BS EN 1999 (Eurocodes 2 to 9).

This is different to the situationadopted by the present BritishStandard codes of practice (e.g.BS 8110, BS 5950 and BS 5628)because with the design Eurocodesthe requirements for achievingsafety, serviceability and durability

and the expressions for actioneffects for the verification of ultimateand serviceability limit states andtheir associated factors of safety areonly given in BS EN 1990. Unlikethe equivalent British Standardcodes of practice the material Euro-codes (BS EN 1992, BS EN 1993,BS EN 1994, BS EN 1995,BS EN 1996 and BS EN 1999) onlyinclude clauses for design anddetailing in the appropriate mate-rial; they require all the material-

independent information for thedesign from BS EN 1990.

The principal objective ofBS EN 1990 is that it sets out for

every Eurocode part the principlesand requirements for achievingsafety, serviceability and durabilityof structures.

BS EN 1990 provides the infor-mation for safety factors for actionsand combination for action effectsfor the verification of both ultimateand serviceability limit states. Itsrules are applicable to the design ofbuilding and civil engineering

frame housing) all need to use theprinciples and rules in BS EN 1990together with the appropriate Euro-codes, thus ensuring a level playingfield, as do the execution standards.

To achieve safety, serviceabilityand durability for structuresBS EN 1990 has requirements to beadhered to by the complete Euro-code suite and construction prod-uct standards on:

p fundamental requirements(safety, serviceability, resistanceto fire and robustness);

p reliability management anddifferentiation;

p design working life;

p durability;

p quality assurance and qualitycontrol.

BS EN 1990, as well as being the

key Eurocode in setting recom-mended safety levels, also intro-duces innovative aspects (listedbelow) that encourages the designengineer to consider the safety ofpeople in the built environmenttogether with responsible consider-ations of economy.

Eurocode: Basis of structural design

Eurocode: Basis of structural designProfessor Haig Gulvanessian CBE, Civil Engineering and Eurocode Consultant

The links between the Eurocodes

EN 1990

EN 1991

EN 1992 EN 1993 EN 1994

EN 1995 EN 1996 EN 1999

Structural safety,serviceability anddurability

Actionsonstructures

Design anddetailing

EN 1997 EN 1998Geotechnical and

seismic design

structures including bridges, masts,towers, silos, tanks, chimneys andgeotechnical structures.

Furthermore construction prod-ucts requiring CE marking (e.g.precast concrete products, metalframe domestic houses and timber

The principal objective ofBS EN 1990 is that it setsout for every Eurocodepart the principles andrequirements for achievingsafety, serviceability anddurability of structures.


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p BS EN 1990 allows reliabilitydifferentiation based on the con-sequences of failure.

p It introduces the concept ofusing the representative valuesof actions and not only the char-acteristic values as used for UKcodes of practice. The loads usedin the BS EN 1990 load combina-tions recognize the appropriatecases where rare, frequent,or quasi-permanent occurringevents are being consideredwith the use of an appropriatereduction coefficient (y) appliedto the characteristic load values,as appropriate. The use of the

representative values for actionsin the load combination expres-sions for ultimate and service-ability limit state verificationsare logical and give economiesfor particular design situations.

p It provides an alternative loadcombination format, giving thechoice to the designer of using

either the expressions 6.10 or6.10a/6.10b for the combinationof actions for ultimate limit stateverification. This choice pro-vides opportunities for econ-omy especially for the heaviermaterials, and can provide flexi-bility with regard to assessment.

p It permits the use of lower fac-tors of safety for loads com-pared to British Standards.Although the effects of actionsaccording to the Eurocodes arelower than UK national codesfor ULS and SLS verification,this should not be a concern tothe industry as the BS EN 1990

values are based on better sci-ence and better research.

p The use of advanced analyticaltechniques for the designer areencouraged, as are the use ofprobabilistic methods shouldthe designer wish to use thesefor more specialized designproblems.

BS EN 1990 is a fully operativecode and the concept of a fullyoperative material-independentcode is new to the European designengineer. It is certainly not a codethat should be read once and thenplaced on the bookshelf. It is thekey Eurocode that sets the require-ments for design, material, productand execution standards. BS EN 1990needs to be fully understood as it iskey to designing structures thathave an acceptable level of safetyand economy, with opportunitiesfor innovation.

A course and a designers guidefor BS EN 1990 are available in the

UK through Thomas Telford Ltd ofthe Institution of Civil Engineers.

Regarding implementation ofBS EN 1990 in the UK, BS EN 1990was published in April 2002 andthe BSI National Annex for Build-ings was published in 2004. The BSINational Annex for Bridges is duein 2009. p


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Eurocode 1: Actions on structures

BS EN 1991, Eurocode 1: Actionson structures, provides compre-hensive information and guidanceon all actions that are usually neces-sary to consider in the design of build-ing and civil engineering structures.

BS EN 1991 comprises 10 differ-ent EN parts (see p. 12). These Partswill provide the characteristic val-ues for actions for use withBS EN 1990, Eurocode: Basis of struc-tural design, and BS EN 1992 toBS EN 1999 as appropriate, fordesign and verification on the basisof the overall principles that aregiven in BS EN 1990.

The following is a brief summaryof the scope, field of applicationand difference with UK practice foreach part of BS EN 1991.

BS EN 1991-1-1, Densities, self-weightand imposed loads for buildings

BS EN 1991-1-1 covers the assess-ment of actions for use in structuraldesign due to:

p the density of construction ma-terials and stored materials;

p the self-weight of structural ele-ments and whole structures, andsome fixed non-structural items;

p imposed loads on floors androofs of buildings (but exclud-

ing snow, which is covered byBS EN 1991-1-3, Snow loads).

The scope of BS EN 1991-1-1 isgreater than for the appropriate UKnational codes (BS 6399-1 andBS 648). There remain some topics(e.g. vertical loads on parapetsand values for actions for storageand industrial use) that are notcovered as comprehensively inBS EN 1991-1-1 when comparedto BS 6399, and these topics will

feature in a complementary docu-ment published by BSI, PD 6688-1-1,which will also provide back-ground information.

BS EN 1991-1-2, Actions onstructures exposed to fire

BS EN 1991-1-2 covers the actions tobe used in the structural design ofbuildings and civil engineeringworks where there is a requirementto give adequate performance in fireexposure. It is intended for use withBS EN 1990 and with the parts onstructural fire design in Eurocodes 2

to 6 and 9. For fire design, fireactions are the dominant action.

The national annex toBS EN 1991-1-2 will refer to a com-plementary document, PD 6688-1-2,which will provide backgroundinformation to the national annex.

are some differences: BS EN 1991-1-3does not apply to sites at altitudesabove 1500 m (the limit in BS 6399-2is 500 m). In the BS EN 1991-1-3snow map, the UK is divided into anumber of zones. An expression isgiven to determine the snow loadon the ground which depends uponthe zone and the altitude of the site.

BS EN 1991-1-4, Wind actions

BS EN1991-1-4 is applicable to:

p building and civil engineeringworks with heights up to 200 m;

p bridges with spans of not morethan 200 m (subject to certainlimitations based on dynamicresponse criteria);

p land-based structures, their com-ponents and appendages.

The specific exclusions are:

p lattice towers with non-parallelchords;

p guyed masts and guyed chimneys;

p cable supported bridges;

p bridge deck vibration fromtransverse wind turbulence;

p torsional vibrations of buildings;

p modes of vibration higher thanthe fundamental mode.

The scope of BS EN 1991-1-4 ismuch wider than BS 6399-2, as itincludes wind actions on otherstructures, which in the UK aregiven in a number of other BritishStandards and design guides. Insome cases, there is no equivalentUK standard, e.g. dynamic re-sponse of certain buildings. Thenational annex to BS EN 1991-1-4will refer to a complementary doc-ument, PD 6688-1-4, which will

give background information tothe national annex and other essen-tial advice.

Eurocode 1: Actions on structuresProfessor Haig Gulvanessian CBE, Civil Engineering and Eurocode Consultant

BS EN 1991-1-3, Snow loads

BS EN 1991-1-3 provides guidancefor the calculation of:

p snow loads on roofs, which occurin calm or windy conditions;

p loads on roofs that occur where

there are obstructions, and bysnow sliding down a pitchedroof onto snow guards;

p loads due to snow overhangingthe cantilevered edge of a roof;

p snow loads on bridges.

BS EN 1991-1-3 applies to:

p snow loads in both maritime (i.e.UK) and continental climates;

p new buildings and structures;

p significant alterations to existing

buildings and structures.

The scopes of BS EN 1991-1-3 andBS 6399-2 are similar. However, there

BS EN 1991 gives uniqueguidance on a particular

type of action.


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BS EN 1991-1-5, Thermal actions

BS EN 1991-1-5 gives principles, rulesand methods of calculating thermalactions on buildings, bridges and

other structures including theirstructural components. Principlesfor determining thermal actions forcladdings and other appendages onthe building are also provided.

Characteristic values of thermalactions are provided for the designof structures that are exposed todaily and seasonal climaticchanges. Structures in which ther-mal actions are mainly a function oftheir use (e.g. chimneys, coolingtowers, silos, tanks, warm and coldstorage facilities, hot and cold serv-ices) are also treated. The character-istic values of isotherms of nationalminimum and maximum shade airtemperatures are provided in theform of maps.

The guidance in this part, in par-ticular the guidance relating tobuilding structures, is not coveredin UK loading standards. Thenational annex to BS EN 1991-1-5will refer to a complementary doc-

ument, PD 6688-1-5, which willprovide background information tothe national annex.

BS EN 1991-1-6, Actions duringexecution

BS EN 1991-1-6 covers assessmentof actions, combinations of actionsand environmental influences dur-ing the execution stage, includingthose actions applied to auxiliary

construction works, e.g. scaffold-ing, propping and bracing, for usein structural design of buildingsand bridges. The safety of peopleon construction sites due to con-struction accidents is not within thescope of this Eurocode part.

The guidance in this part is notcovered in UK loading standards.

BS EN 1991-1-7, Accidental actions

BS EN 1991-1-7 describes safetystrategies for accidental design sit-uations. It recommends design val-ues for the most common cases of

accidental actions from impact andexplosion; it gives design modelsand detailed provisions that may beused as alternatives to design veri-fications. It also provides moreadvanced impact and explosiondesign concepts than which werefound in British Standards.

External explosions, warfare,sabotage or risk scenarios due tonatural phenomena, such as torna-does, extreme erosion or rock falls,are not in the scope of thisEurocode part.

Although aspects of accidentalactions are covered in BS 6399-1 andBS 5400, BS EN 1991-1-7 compre-

hensively covers the topic of acci-dental actions in one document. Acategorization scheme concerningthe robustness of buildings, whichhas also been used in ApprovedDocument A of the Building Regu-lations, is introduced in BS EN 1991-1-7. The UK design engineer will befamiliar with the design require-ments of this part although riskassessments will be required forsome categories of structures.

The national annex toBS EN 1991-1-7 will refer to a com-plementary document, PD 6688-1-7,which will give background infor-mation to the National Annex, inparticular to risk assessments onimpacts to supporting structuresfor bridges.

BS EN 1991-2, Traffic loads onbridges

BS EN 1991-2 specifies imposedloads (models and representativevalues) associated with road traffic,pedestrian actions and rail traffic,that include, when relevant,dynamic effects and centrifugal,braking, acceleration and acciden-tal forces. It also includes guidanceon combinations with non-trafficloads on road and railway bridges,and on loads on parapets.

The national annex toBS EN 1991-2 will refer to a comple-

mentary document, PD 6688-2,which will give background infor-mation to the national annex.

BS EN 1991-3, Actions induced bycranes and machinery

BS EN 1991-4 specifies actions, self-weights and imposed loads (models

and representative values) associ-ated with hoists, crabs and craneson runway beams, and static anddynamic actions induced in sup-porting structures by machinery.

BS EN 1991-4, Actions in silos andtanks

BS EN 1991-3 gives general princi-ples and rules for determiningactions arising from the storage ofbulk materials and liquids in silosand tanks. The scope is restricted to:

p silos with limited eccentricity ofinlet and outlet, with smallimpact effects caused by filling,and with discharge devices thatdo not cause shock or eccentric-ities beyond the givenlimitations;

p silos containing particulatematerials which are free-flowingand have a low cohesion;

p tanks with liquids stored at nor-mal atmospheric pressure.

Difference betweenBS EN 1991 and the UKsystem of loading codes

Each part of BS EN 1991 givesunique guidance on a particulartype of action. Within each partguidance is provided for buildingsand other construction works (e.g.

bridges). This is different to the BSIsystem of loading codes where thecodes are based on the type ofstructure, e.g. BS 6399 for buildingsand BS 5400 for bridges.

Industry initiatives

A course for BS EN 1991 is availablein the UK through Thomas TelfordLtd of the Institution of Civil Engi-neers. Two designers guides, thefirst covering Actions on Buildingsand the second covering Actions onBridges will be published in 2009 byThomas Telford Ltd. p



24/52

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Eurocode 2: Design of concrete structures

The Eurocode process began over30 years ago and is nearing fullimplementation. The concrete sec-tor has been leading the way withthe new codes. Designers and engi-neers can now design usingEurocode 2. The full package of thecode, including all its nationalannexes and supporting documen-tation, is in place and is being usedon projects. The UK committee isno longer supporting BS 8110.

Like it or not, the introduction ofthe Eurocodes is inevitable so itseems best to accept this and resolveto make the change as easy as possi-ble. With this in mind, The ConcreteCentre as part of the ConcreteIndustry Eurocode 2 Group has notonly developed a transition strategy

but has delivered this via a widerange of resources. These include acompanion guide Concise Eurocode 2,and a series of guides under the ban-ner How to design concrete structuresusing Eurocode 2. The series of Howto... leaflets was released in early2006 and have now been gatheredtogether and published as a com-pendium, which includes new chap-ters on Retaining Walls andDetailing. Precast Eurocode 2: Design

Manual and Precast Eurocode 2:Worked Examples, have been pub-lished by British Precast. ConciseEurocode 2 for Bridges will be pub-lished by the Concrete Centre inearly 2009. In addition, a dedicatedwebsite www.eurocode2.info hasbeen set up. This site contains expla-nations, news, key information anddownloads, and, in particular, aseries of detailed worked examples.

The Concrete Centre togetherwith the Modern Masonry Alliance

has jointly published a series ofthree guides called How to DesignMasonry Structures Using Eurocode 6explaining Eurocode 6. Eurocode 6

introduces a new classification ofmasonry units and also a newdesign approach for masonry mem-bers in compression.

Despite the cost of changing tothe new codes, there will be eco-nomic benefits to be gained fromtheir use. In concrete design it isexpected that there will be materialcost savings of up to 5% comparedwith using BS 8110. Furthermore,the Eurocodes are organized toavoid repetition, they are techni-cally advanced and should offermore opportunities for UK design-ers to work throughout Europe.Plus any delay in implementing theEurocodes will diminish the abilityof UK designers and engineers to

material Eurocodes, such as basis ofdesign, actions, geotechnics, is a bigenough challenge itself, therefore todo this alongside just one materialis a much simpler proposition.Concrete lends itself to being thetrailblazer material for a number ofreasons. Firstly, Eurocode 2 for con-crete has only four parts, secondly,the national annexes are all pub-lished and guidance on them isreadily available and thirdly, almostevery project has concrete in itsomewhere.

Another early decision is whetherto train an individual or two, agroup, or the majority of staff. In-house experts can be sent on in-depth external courses and thenrelay the knowledge gained by act-

ing as a conduit for Eurocoderelated queries within the officeand subsequently training their col-leagues. The risk with this strategyis that the expert may not be up tothe task, they may leave the prac-tice, or simply will not have thetime to act as a mentor to the wholepractice. The additional issue ofwho to choose as the potentialEurocode expert can be such aproblem that this approach is often

rejected.Some practices are instead choos-ing to pioneer the Eurocodesthrough specific projects. Thisenables a broad base of expertise todevelop and chooses the experts bydefault. Those sent on trainingcourses can apply their knowledgeat once on real life projects withhelp readily available from thestructural engineering departmentat The Concrete Centre. UsingEurocodes for specific projects pro-

vides a broader base of expertisecompared with having a singlechampion. A further advantage isthat focusing on specific projects

Eurocode 2: Design of concrete

structuresDr Andrew Minson, The Concrete Centre

work on projects in the rest ofEurope whilst permitting firmsfrom Continental Europe to workover here.

Moving over to Eurocode designis going to be a huge commitmentbut when designers want to makethe transition the concrete industryis ready to help. The Concrete Cen-tres regional technical team havenoticed that practices are adoptingan arrangement of Eurocode imple-mentation strategies.

The initial decision for a practiceto make is whether to implement all

the material Eurocodes at once or tochoose one single material as thetrailblazer. The advantage of this isthat wrestling with all the non-

In concrete design it isexpected that there willbe material cost savingsof up to 5% comparedwith using BS 8110.


27/52



limits the practices exposure toEurocodes until more confidenceand knowledge is gained. In theshort term, this approach limits theinevitably increased design time toa single project, allows lessons to belearnt and permits an understand-ing on how to effectively train staff.The final option is to train all staffand implement on all projects com-mencing after a certain date.

Whatever strategy is imple-mented in the office, employeeswill need to be trained. This may beface-to-face, through self-learningor by distance learning. A range ofcourses has been developed by

The Concrete Centre to meet thedemands of face-to-face training(see box).

An alternative is to have a periodof distance self-learning, usingguidance and publications ofworked examples with access to ahelpline. This could prove benefi-cial if sandwiched between intro-duction and lessons learntface-to-face sessions.

The new Eurocodes should beviewed as a challenging opportu-nity and the concrete sector hasrisen to the challenge and donemuch to develop a range of tools tohelp realize this opportunity. p

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Eurocode 2 Resources

PublicationsConcise Eurocode 2Published by The Concrete Centre

This publication summarises the information that will be commonly usedin the design of reinforced concrete framed buildings to Eurocode 2 and itsUK National Annex and provides explanations to all necessary clauses. Withextensive clause referencing to Eurocode 2 and other relevant Eurocodes,design tables and column charts, the publication is self-sufficient and alsoacts as a manual to the code.

Precast Eurocode 2 Part 1: Design manualPrecast Eurocode 2 Part 2: Worked examplesPublished by British Precast

Part 1 provides a summary of the basis of precast concrete design to Eurocode 2and offers guidance through the new code, the UK National Annex and otherrelevant Eurocodes. The sister publication, Part 2, complements Part 1 andtogether they aim to promote an understanding of Eurocode 2 for precastconcrete. Designers will find them useful companion documents to the newcode both during the transition period and beyond.

How to Design Concrete Structures to Eurocode 2Published by The Concrete Centre

This publication aims to make the transition to Eurocode 2: Design of ConcreteStructures and its National Annex as easy as possible by drawing together inone place the key information and commentary required for the design oftypical concrete elements. Chapters include: Getting Started; Foundations;Slabs; Flat slabs; Beams; Deflections; Columns; Retaining walls and Detailing.

Properties of Concrete for use in Eurocode 2Published by The Concrete Centre

In the design of concrete structures, engineers have the flexibility to specifyparticular concrete type(s) aimed at meeting the specific performancerequirements for their project. This guide is aimed at design engineers toprovide them with a greater knowledge of concrete behaviour, so that theycan optimise the use of the material aspects of concrete in their design.Guidance is given on the properties of concrete for design to Eurocode 2 andthe corresponding UK national annex.

To assist designers with the application of Eurocode 2, a range of technical

design guidance is available from the cement and concrete industry.

For more information visitwww.eurocode2.info

www.eurocode2.info

SoftwareRC SpreadsheetsPublished by The Concrete Centre

The release of Version 3 of the spreadsheets follows the publication ofEurocode 2 plus its UK National Annex and the publication ofAmendment 3 to BS 8110 Part 1: 1987. The spreadsheets allow the rapidproduction of clear and accurate design calculations and facilitate theexamination of a wide range of what if scenarios. For more information visitwww.concretecentre.com/rcdesign.

Training and CPDsThe Concrete Centre provides various Eurocode 2 training courses - whichrange from half-day courses for those already familiar with the design ofconcrete buildings to a comprehensive two-day workshop which covers allsections of the new code and explores its practical application with workedexamples. Visit www.concretecentre.com/eventsfor further information.


29/52

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Introduction

The primary encouragement toUK designers is that the struc-tural mechanics has not changed the steel behaves in the same way,no matter which code is used to checkresistance. The second encourage-

ment is that familiarity with theEurocode 3 (BS EN 1993-1-1) willbring the realization that the samedesign checks are being executed inBS 5950 and Eurocode 3, althoughthe presentation may be slightlydifferent.

Loading

Although this article primarily con-cerns resistance, the loading side of

the relationship is also important.Load combinations are found inEN 1990, and together with thenational annex for that code, theresults will bring benefits to UKdesign. For strength design, mosteconomy will be realized by usingexpression 6.10b (the nomenclaturewill become familiar in time) whichwill be the key expression in mostcircumstances. Under this loadcombination, elements that onlyexperience vertical loads, such asfloor beams, will be designed for1.25 permanent actions + 1.5 variable actions. This is an immedi-ate attraction compared to BS 5950,which would have floor beamsdesigned for 1.4 dead loads +1.6 imposed loads.

Systems carrying wind loads, suchas bracing, will experience largerdesign loads, because in load com-binations where the leading vari-able action is identified as the wind,

it will attract a load factor of 1.5.Additionally, the Eurocode equiva-lent to BS 5950s notional horizontalloads (NHF) known as equivalent

horizontal loads (EHF), appear inevery load combination and inaddition to the heavier wind loads.

Resistance

Three noticeable general changes are:

p the different nomenclature in EC3;p the layout of the standard,

which is arranged by structuralphenomena, not design processand thus will be unfamiliar;

p the presentation of code checksby equation, rather than in look-up tables, and a lack of charts.

on 1/200, which is of course the0.5% of BS 5950.

Cross sectional resistance

As expected, there are no signifi-cant changes here. Shear resistancehas almost trivial changes, with a

modest change in the shear area. InBS 5950, the shear resistanceinvolves a factor of 0.6 in EC3 thefactor is 1/3, which is 0.577. Thisillustrates that, often, the differencesare very small.

Buckling

In both strut buckling and lateraltorsional buckling, UK designerswill find a different presentation.

Slenderness for strut buckling iscalled l calculated as l = (Aft/Ncr)where Ncr is the Euler buckling load.It can be demonstrated algebraicallythat the expression for l is inextri-cably linked to l/ryy as calculated innational standards the Eurocodeslenderness is l/ryy divided by afactor approximately 90. Eitherapproach may be used to calculatethe EC3 slenderness. Having calcu-lated the slenderness, there is noabsolute value of design stress cal-culated in the Eurocode. The resist-ance is always based on a reductionfactor, multiplied by the yieldstrength. This means that a multi-tude of tables displaying values ofpc andpb are not required just twosingle expressions.

For strut buckling, values arevery close to those determined inaccordance with BS 5950. For lateraltorsional buckling (LTB), the resist-ances according to the Eurocode are

generally significantly higher approximately 25% for middlerange Universal Beams. AlthoughLTB does not govern all members,

Eurocode 3: Design of steel structures

Eurocode 3: Design of steel

structuresDavid Brown, Deputy Director, Steel Construction Institute

All are issues of presentation, andwill be managed as designersbecome familiar with the standard.Engineers will recognize a close andtransparent link with the underly-

ing structural mechanics (whichwas often opaque in BS 5950), usingvalues such as the Euler load, forexample. In many cases simplespreadsheets can be used to re-create look-up tables if needed.

Frame stability

This is almost the same as BS 5950.lcr of BS 5950 becomes acr in EC3,with a very similar calculation. Thefamiliar limit of 10, above which

second order effects are smallenough to be ignored, and belowthat an amplifier, which is the samein both standards. EHF are based

The same design checks

are being executed inBS 5950 and Eurocode 3,although the presentationmay be slightly different.


31/52

the Eurocode has a valuable advan-tage when it does.

Combined axial load and

bendingWith an axial term, a mayor axisbending term and a minor axisbending term, the expressions inthe Eurocode look innocent.Designers will find the interactionfactors that precede the bendingterms appear far from straightfor-ward, but spreadsheets are alreadyavailable to ease the calculation(www.steelbiz.org).

ConnectionsWith one exception, no significantchanges will be found in connec-tion design. Bolts have very similarshear and tensile resistances, andweld strengths are similar to thosein BS 5950. The resistance of stan-dard flexible end plates is still gov-

erned by shear in the beam web, forexample. The major change is in thebearing resistance of bolts, which issignificantly higher than thenational standard.

Support tools

Like most sectors, the steel commu-nity has been very active in preparingsupport materials. The ubiquitousBlue Book will be available, along-side a whole series of other guides,including worked examples, a con-cise guide, connection guides and aguide to multi-storey frames. Theseare the first of many that will beproduced (www.shop.steelbiz.org).Significant resources are availableonline (www.access-steel.com) andsoftware will be available.

Conclusions

For the steel designer, once familiarwith the appropriate documents (a

significant task, as this includes themany parts of the Eurocodes, thenational annexes and other supportinformation), and familiar with thelayout of the clauses within theStandard, the process will be reas-suringly similar to design toBS 5950. This general observationhas some exceptions, such as com-bined axial loads and bending, butwith some thought, it is easy to seethat the underlying principles ofstructural mechanics are the samein both standards. In many ways,more recent versions of BS 5950have done a good job of introduc-ing designers to issues such as

frame stability, which will be seenin a very similar format in theEurocode.

The steel knows no different, andthe structural mechanics has notchanged. In time, this new standardfor steel design will become afamiliar friend. p


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Eurocode 4 brings both benefitsand challenges to UK designerswho are familiar with the earlier nat-ional standards for composite steeland concrete structures. Eurocode 4consists of three parts: Part 1-1,General rules and rules for buildings;

Part 1-2, General rules Structuralfire design; and Part 2, General rulesand rules for bridges. To enable Euro-code 4 to be used, designers alsoneed to make reference to the Euro-codes dealing with the design of con-crete and steel structures, BS EN 1992and BS EN 1993, respectively.

Before the Eurocodes can beused, designers need another docu-ment called the national annex(NA) which specifies the appropri-

ate partial safety factors that needto be used for structures built in aparticular country. In addition topartial safety factors, there are somechoices given in the Eurocodes toallow different nations to controlthe design methods used in theirterritory; these parameters arecalled Nationally Determined Para-meters (NDPs). The NA may alsoinclude reference to non-conflictingcomplementary information (NCCI),which provides designers withinformation that is not given inEurocodes themselves, such asmaterial from earlier national stan-dards or design guides. For thedesign of steel structures, the web-site www.steel-ncci.co.uk will belisted in the UK NA to Eurocode 3and Eurocode 4, and will provideall the necessary NCCI to theseEurocodes.

To assist designers in under-standing Eurocode 4, references [1],

[2] and [3] provide backgroundinformation on the origin andobjectives of the code provisions;this is supplemented by a selection

of worked examples that illustratethe use of a particular clause. Inaddition, background informationis freely available through theEurocodes website of the EuropeanCommission Joint Research Centre(http://eurocodes.jrc.ec.europa.eu).

One of the major changes for UKdesigners familiar with compositeconstruction is that the Eurocodesmake greater use of first principlesand, owing to the fact that thereis little duplication of material,a number of standards and theircorresponding NAs will need tobe consulted when designing astructural element. However, dueto their much wider scope, theEurocodes bring a number of ad-

vantages to designers when com-pared to earlier national standards.For example, asymmetric steel sec-tions that possess a much largerbottom flange in relation to the topflange are very efficient when usedin composite beams. As opposed tothe earlier national standard forbuildings, BS EN 1994-1-1 permitsthe designer to use steel sections ofthis type through rules for compos-ite beams with partial shear con-nection. Moreover, for compositebridges, pilot studies undertakenfor the Highways Agency haveindicated that the new structuralEurocodes produce more economicdesigns compared to those usingthe earlier national standards [4].

As well as improving on rulescontained in the earlier nationalstandards, the Eurocodes also per-mit designs to be undertaken onstructures where there previouslyhad been an absence of codified

rules. This is particularly true forcomposite columns, which, althoughpopular internationally due to theirslender lines and enhanced resist-

ance for both normal and fire con-ditions, have not been widely usedin UK buildings to date.

Following the publication of theUK NAs, the Steel ConstructionInstitute (SCI) will be issuing asuite of design guides that provide

advice on designing structural ele-ments and frames using theEurocode provisions, together witha full set of worked examples. Inaddition to the design guides, theEuropean steel industrys multi-lingual Eurocode 3 and Eurocode 4website, Access Steel (www.access-steel.com), provides free access to50 interlinked modules on detaileddesign of elements, free element-design software, and interactive

worked examples. To complementthe design guides and electronicresources, training courses onEurocode 4 are being provided byThe Institution of Civil Engineers,The Institution of Structural Engi-neers and SCI.

References

[1] Johnson, R.P. and Anderson, D.Designers Guide to EN 1994-1-1:

Eurocode 4: Design of Composite Steeland Concrete Structures, Part 1-1:General Rules and Rules for Buildings,Thomas Telford, London, 2004

[2] Moore, D., Bailey, C., Lennon, T.and Wang, Y. Designers Guide toEN 1991-1-2, EN 1992-1-2, EN 1993-1-2 and EN 1994-1-2, ThomasTelford, London, 2007

[3] Hendy, C.R. and Johnson, R.P.Designers Guide to EN 1994-2Eurocode 4: Design of Composite Steeland Concrete Structures Part 2, GeneralRules and Rules for Bridges, ThomasTelford, London, 2006

[4] Hendy, C.R. Implications of thechange to Eurocodes for bridgedesign, Proceedings of the Institutionof Civil Engineers: Bridge Engineering,161, March 2008, pp3-10 p

Eurocode 4: Design of composite

steel and concrete structuresDr Stephen Hicks, Manager Structural Systems, Heavy Engineering Research Association, Manukau City,New Zealand (formerly Senior Manager Building Engineering, Steel Construction Institute, UK)


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Corus and our partners in the UK steel

construction industry are ready to help

designers through the transition from

British Standards to EC3 and EC4,

providing practical design guidance,

technical support and training courses.

To find out what is available visit

www.corusconstruction.com/eurocodes

Structural Design EurocodesWell guide you through


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Introduction

BS EN 1995 is in three parts:p Part 1-1: General. Common rules

and rules for buildings

p Part 1-2: General. Structural firedesign

p Part 2: Bridges

With BS EN 1990 and three stan-dards which provide essentialmaterial properties (BS EN 338,Structural timber Strength classes,BS EN 1194, Timber structures Glued laminated timber Strengthclasses and determination of character-istic values, and BS EN 12369, Wood-based panels Characteristic values forstructural design) Eurocode 5 will

replace BS 5268, Parts 2, 3, 4 and 6.

Key changes

The key changes for designersfamiliar with BS 5268 will be:

p the differentiation between ulti-mate, serviceability and acci-dental limit states;

p the partial factor format, whichrequires safety factors to beapplied manually to both loadsand material properties, ratherthan having them all built intotabulated grade or basic values;

p new symbols and materialstrength modification factors;

p that BS EN 1995 is a theoreticaldesign code rather than a codeof best practice, so formulaereplace tabulated values andmost of the helpful advice givenin BS 5268 has disappeared.

Principal benefits

p As with other Eurocodes, multi-national companies will benefit

by being able to use the sametimber design code in many dif-ferent countries both within andoutside Europe [1].

p Using a similar design format tothat used for other structuralmaterials will help to make tim-ber design more accessible.

p The separation of ultimate andserviceability design states per-mits the use of more rationaldesign limits a Buro Happoldengineer stated that the award-winning Sheffield Winter Gar-den glulam roof could not havebeen designed to BS 5268.

complex, particularly for thedesign of connections, floors,deflections and fire.

p The loss of much helpful guid-ance such as standard bracingfor trussed rafter roofs, stabledepth-to-breadth ratios forbeams, and the wind shieldingeffect of masonry attached totimber frame buildings, meansthat supporting publicationswill be required.

p No guidance for the design ofglued joints is provided valueshave to be obtained from tests.

p The code and its numerous sup-porting standards will cost con-siderably more.

ChallengesSome challenges for designers willbe:

p learning the new symbols;

p determining the critical loadcase for combined loads of dif-ferent durations;

p remembering which materialmodification factors to use (inparticular reducing the tabulatedcharacteristic values to allow for

load duration);p designing trussed rafter roofs,

which involves dozens of differ-ent load combinations and loadcases;

p demonstrating the strength andstability requirements for timberframe walls with only minimalguidance;

p calculating the design resistanceof connections.

Effects on the timber industry

Major changes in timber usage andspecification are unlikely. However:

Eurocode 5: Design of timber

structuresArnold Page, Structural Timber Engineering Consultant

p The separation of principles andapplication rules allows theengineer more freedom butrequires more understanding onhis or her part.

p The direct use of characteristictest values simplifies the adop-tion of new timber materials

and components.p The connection design formulaecan cater for LVL, OSB and chip-board as well as for solid timbermaterials.

p The dedicated timber bridgedesign code should facilitateand encourage the use of timberin lightweight bridges.

p The formulaic approach facili-tates the development of spread-sheets and software.

Chief disadvantages

p Structural calculations to EC5are generally considerably more

Major changes in timber

usage and specificationare unlikely


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Eurocode 5: Design of timber structures

p characteristic strength proper-ties for panel products and com-ponents such as timber I-joistsand metal hardware must nowbe obtained in accordance withCEN testing standards;

p floors may have to be a littlestiffer (i.e. more timber);

p large roof structures withoutbrittle finishes may not requireso much timber;

p there will have to be yet morereliance on software for thedesign of trussed rafters, con-nections and timber framewalls.

General guidance andpublications

Various manuals and guidancedocuments have been published

in the UK, and many of theseare listed on the Eurocodes Expertwebsite [2] under Timber/Pub-lications. STEP, which is a two-volume publication written byEuropean experts, provides excel-lent background material and use-ful design examples. TRADA runscourses on Eurocode 5 in conjunc-tion with the Institution of Struc-tural Engineers, and during 2009 itwill be completely updating itsexisting Eurocode 5 design aids,design examples and software.Manual for the design of timber build-ing structures to Eurocode 5 [3]includes a CD which has spread-

sheets for connection design.Finally BSI intends to preserve theguidance in BS 5268, which wouldotherwise be lost, by producing anew publication of complementary

information for use with Eurocode 5(PD 6693).

Summary

With supporting information Euro-code 5 is a workable design codewhich is particularly useful formulti-national companies and thedesigners of larger engineeringstructures and bridges.

References

[1] The Structural Engineer, 18 September2007. The Institution of Structural

Engineers, London[2] http://www.eurocodes.co.uk[3] Manual for the design of timber build-

ing structures to Eurocode 5, TheInstitution of Structural Engineers/TRADA, December 2007 p


For more information please visit:www.bsigroup.com/BSOLconstruct

BritishStandardsOnline (BSOL)Access to British Standards directfrom your desktop

www.bsigroup.com/BSOLconstruct

Marketing reference 2159-AC


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Eurocode 6 (BS EN 1996) followsthe general presentation of thematerial Eurocodes in that Part 1-1covers the design of plain and rein-forced masonry whilst Part 1-2deals with structural fire design.There are two further parts: Part 2which deals primarily with theselection of materials and executionof masonry and Part 3, which coverssimplified calculation methods forunreinforced masonry structures.

BS 5628 was the first limit statedesign code for masonry in theworld and UK designers are veryfamiliar with the principles thathave now been encapsulated inEurocode 6. There are, however, afew major changes that UK designerswill need to become familiar with.

During the drafting of Eurocode6, a way had to be found to dealwith the wide range of masonryunits used across Europe. Thisrange not only includes differentmaterial such as clay, concrete andstone, but also a variety of configu-rations based upon the proportionand direction of any holes or perfo-rations, web thickness etc. This hasresulted in four groupings ofmasonry units. The UK only has

experience of Group 1 and Group 2masonry units but no doubtGroup 3 and Group 4 units willfind their way to the UK.

The characteristic compressivestrength of masonry is no longerpresented in the form of tables butas an equation. This equationincludes the normalized strength ofthe masonry and the strength of themortar. The normalized strength isnew to the UK and relates the com-pressive strength of the unit deter-

mined by test to a standardizedshape and moisture content. Thedesignation of mortars has alsochanged with the need for a decla-

ration based on strength ratherthan mix proportions. Thus an M12mortar may be expected to have astrength of 12 N/mm2.

A key aspect of the standardssupporting Eurocode 6 is that onlymasonry units are referred to, leav-ing the various UK NationalAnnexes to specify standard sizesfor bricks and blocks and how tospecify, using performance stan-dards, such things as engineeringbricks.

and suitable values of partial safetyfactors have been introduced.

Fire design will largely remain inthe form of tables similar to thosecontained in BS 5628-3. The fireresistance of a load-bearing wallnow comprises two values depend-ing upon how highly loaded thewall is and is further enhanced ifthe wall is plastered.

Part 2 of Eurocode 6 (BS EN 1996-2) contains limited information of avery general nature on materialsand execution. Five new exposureclassifications MX1 to MX5 aredefined. Part 2 is not, however, areplacement for the extensive guid-ance provided in BS 5628 and it isintended that this information,together with some guidance gar-

nered from BS 5628-1 and -2, willform the basis of a PD to be pub-lished by BSI.

Part 3 (BS EN 1996-3) deals withsimplified calculation methods forunreinforced masonry but it is notanticipated that this will be widelyused in the UK where other guid-ance, for example Approved Docu-ment A of the Building Regulationsfor England and Wales, is likely toproduce

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