Designers' Guide to Eurocode 8 - Design of Bridges for Earthquake Resistance EN 1998-2

248 Pages·2012·5.96 MB·English

by  Kolias

DESIGNERS’ GUIDES TO THE EUROCODES
DESIGNERS’ GUIDE TO EUROCODE 8:
DESIGN OF BRIDGES FOR EARTHQUAKE
RESISTANCE
EN 1998-2
BASIL KOLIAS
DENCO S.A, Greece
MICHAEL N. FARDIS
University of Patras, Greece
ALAIN PECKER
Ge´odynamique et Structure, France
Series editor
Haig Gulvanessian CBE
PublishedbyICEPublishing,40MarshWall,LondonE149TP
FulldetailsofICEPublishingsalesrepresentativesanddistributorscanbefoundat:
www.icevirtuallibrary.com/info/printbooksales
EurocodesExpert
StructuralEurocodesoffertheopportunityofharmoniseddesignstandardsfortheEuropeanconstruction
marketandtherestoftheworld.Toachievethis,theconstructionindustryneedstobecomeacquainted
withtheEurocodessothatthemaximumadvantagecanbetakenoftheseopportunities.
EurocodesExpertisanICEandThomasTelfordinitiativesetuptoassistincreatingagreaterawareness
oftheimpactandimplementationoftheEurocodeswithintheUKconstructionindustry.
EurocodesExpertprovidesarangeofproductsandservicestoaidandsupportthetransitiontoEurocodes.
For comprehensive and useful information on the adoption of the Eurocodes and their implementation
[email protected]
www.icevirtuallibrary.com
AcataloguerecordforthisbookisavailablefromtheBritishLibrary
ISBN978-0-7277-5735-7
#ThomasTelfordLimited2012
ICEPublishingisadivisionofThomasTelfordLtd,awholly-ownedsubsidiaryoftheInstitutionofCivil
Engineers(ICE).
Allrights,includingtranslation,reserved.ExceptaspermittedbytheCopyright,DesignsandPatentsAct
1988,nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmittedinanyform
orbyanymeans,electronic,mechanical,photocopyingorotherwise,withoutthepriorwrittenpermissionof
thePublishingDirector,ICEPublishing,40MarshWall,LondonE149TP.
Thisbookispublishedontheunderstandingthattheauthorsaresolelyresponsibleforthestatementsmade
andopinionsexpressedinitandthatitspublicationdoesnotnecessarilyimplythatsuchstatementsand/or
opinionsareorreflecttheviewsoropinionsofthepublishers.Whileeveryefforthasbeenmadetoensure
thatthestatementsmadeandtheopinionsexpressedinthispublicationprovideasafeandaccurateguide,
noliabilityorresponsibilitycanbeacceptedinthisrespectbytheauthorsorpublishers.
AssociateCommissioningEditor:JenniferBarratt
ProductionEditor:ImranMirza
MarketSpecialist:CatherinedeGatacre
TypesetbyAcademicþTechnical,Bristol
IndexcreatedbyIndexingSpecialists(UK)Ltd,Hove,EastSussex
PrintedandboundbyCPIGroup(UK)Ltd,Croydon,CR04YY
Preface
Aim of the Designers’ Guide
This Designers’ Guide to EN 1998-2:2005 covers the rules for the seismic design of bridges,
following in a loose way the contents of this EN Eurocode. It highlights its important points
without repeating them, providing comments and explanations for its application, as well as
background information and worked-out examples. However, it does not elaborate every
singleclause inEN 1998-2:2005, neither does it followstrictly the sequence of its clauses.
Layout of this guide
All cross-references in this guide to sections, clauses, subclauses, paragraphs, annexes, figures,
tables and expressions of EN 1998-2 and EN 1998-5 are in italic type, which is also used
wheretextfromEN1998-2andEN1998-5hasbeendirectlyreproduced(conversely,quotations
from other sources, including other Eurocodes, and cross-references to sections, etc., of this
guide, are in roman type). Numbers within square brackets after cross-references in the
marginrefertoParts1,2and5ofEN1998:EN1998-1[1],EN1998-2[2],EN1998-5[3].Expres-
sion numbers specific to this guide are prefixed by D (for Designers’ Guide), for example,
Eq. (D3.1), to prevent confusion with expressionnumbersfrom EN 1998.
Acknowledgements
This Designers’ Guide would not have been possible without the successful completion of
EN 1998-2:2005. Those involved in the process were:
g nationaldelegatesand nationaltechnicalcontacts toSubcommittee 8 ofCEN/TC250
g theProject Team of CEN/TC250/SC8that worked for the conversion from the ENV to
theEN:namely PT4, convenedby Alex Plakas.
v
Contents
Preface v
Aim ofthe Designer’s guide v
Layout ofthis guide v
Acknowledgements v
Chapter 1 Introductionand scope 1
1.1. Introduction 1
1.2. Scope of Eurocode8 1
1.3. Scope of Eurocode8 Part2 2
1.4. Use of Eurocode 8Part2 with theother Eurocodes 2
1.5. Additional European standardsto be used with EN 1998-2:2005 3
1.6. Assumptions 4
1.7. Distinction between principles and application rules 4
1.8. Terms and definitions– symbols 4
References 4
Chapter 2 Performance requirements andcompliance criteria 5
2.1. Performance-based seismic design of bridges 5
2.2. Performance requirementsfornewbridges in Eurocode 8 7
2.3. Compliance criteriafor the non-collapserequirement and
implementation 8
2.4. Exemption from the application of Eurocode 8 16
References 16
Chapter 3 Seismic actions and geotechnical aspects 19
3.1. Design seismic actions 19
3.2. Siting and foundation soils 29
3.3. Soil properties and parameters 30
3.4. Liquefaction, lateral spreading and related phenomena 32
References 36
Chapter 4 Conceptualdesign ofbridges forearthquake resistance 37
4.1. Introduction 37
4.2. Generalrulesfortheconceptualdesignofearthquake-resistantbridges 38
4.3. The choice ofconnection between the piers and the deck 43
4.4. The piers 53
4.5. The abutments and their connection with the deck 59
4.6. The foundations 64
References 65
Chapter 5 Modelling and analysis ofbridgesfor seismic design 67
5.1. Introduction: methods of analysis inEurocode 8 67
5.2. The three components ofthe seismic action in the analysis 68
5.3. Design spectrum forelastic analysis 69
5.4. Behaviour factorsfor theanalysis 69
5.5. Modal response spectrumanalysis 73
5.6. Fundamental mode analysis(or ‘equivalent static’ analysis) 92
5.7. Torsional effects in linear analysis 98
5.8. Effective stiffness forthe analysis 100
5.9. Calculationof seismic displacementdemandsthrough linearanalysis 107
5.10. Nonlinearanalysis 110
References 117
vii
Chapter 6 Verification and detailingof bridge components for earthquakeresistance 119
6.1. Introduction 119
6.2. Combination ofgravityandotheractions withthe design seismic
action 119
6.3. Verification procedure indesign forductility using linear analysis 122
6.4. Capacity design of regions other than flexural plastic hingesin
bridges of ductile behaviour 124
6.5. Overview of detailing and design rules forbridges with ductile or
limited ductile behaviour 129
6.6. Verification and detailing of joints betweenductile pier columns and
the deck or a foundation element 129
6.7. Verificationsin thecontext of design for ductilitybasedon nonlinear
analysis 132
6.8. Overlap and clearancelengths atmovablejoints 135
6.9. Seismic links 140
6.10. Dimensioning ofbearings 142
6.11. Verification of abutments 155
6.12. Verification of thefoundation 159
6.13. Liquefaction and lateral spreading 164
References 167
Chapter 7 Bridges with seismic isolation 171
7.1. Introduction 171
7.2. Objective, means, performance requirementsandconceptual design 171
7.3. Design seismic action 174
7.4. Behaviour families of themost common isolators 174
7.5. Analysis methods 185
7.6. Lateral restoring capability 191
References 191
Chapter 8 Seismicdesign examples 193
8.1. Introduction 193
8.2. Example of a bridge withductile piers 193
8.3. Example of a bridge withlimited ductile piers 210
8.4. Example of seismic isolation 221
References 249
Index 251
viii
Designers’GuidetoEurocode8:DesignofBridgesforEarthquakeResistance
ISBN978-0-7277-5735-7
ICEPublishing:Allrightsreserved
http://dx.doi.org/10.1680/dber.57357.001
Chapter 1
Introduction and scope
1.1. Introduction
Design of structures for earthquake resistance penetrated engineering practice for buildings
much earlier than for bridges. There are several reasons for this. First, seismic design is of rel-
evance mainly for piers, but is secondary for the deck. The deck, though, receives in general
far more attention than the piers, as it is more important for the function and the overall cost
of the bridge, while its engineering is also more challenging. So, seismic considerations, being
relevant mainly for the less important components of bridges, have traditionally been of lower
priority. Second, a good number of bridges are not so sensitive to earthquakes: the long-span
ones – which are also the subject of lots of attention and of major design and engineering
effort– are very flexible, and their long periods of vibration are outside the frequency range of
usual ground motions. At the other extreme, short bridges, with one or only few spans, often
follow the ground motion with little distress, and normally suffer only minor damage.
However, with the very rapid expansion of transportation networks, the new priorities in land
use–especiallyinurbanareas–andthesensitivitiesofrecenttimestoprotectionoftheenviron-
ment,bridgeengineeringhasspreadfromthetraditionalfieldofshortcrossingsofrivers,ravines
orothernaturalbarriersorofover-andunderpassesformotorwaystolongviaductsconsisting
of a large number of spans on equally numerous piers, often crossing territories with different
ground or soil conditions. The heavy damage suffered by such types of engineering works in
the earthquakes of Loma Prieta in 1989 and Kobe in 1995 demonstrated their seismic vulner-
ability. More recent events have confirmed the importance of proper seismic design (or lack of
it) forbridge projects.
Owingtothesedevelopments,recentdecadeshaveseenmajoradvancesintheseismicengineering
ofbridges.Itmaynowbeclaimedwithacertainamountofconfidencethatthestate-of-the-artin
theseismicdesignofbridgesiscatchingupwiththatofbuildings,whichismoredeeplyrootedin
common design practice and codes. Europe, where even the moderate-to-high seismicity
countriesofthesouthlackedmodernseismicdesigncodesforbridges,hasseenthedevelopment
ofEN1998-2:2005asamodern andcompleteseismicdesignstandard,onparwithitscounter-
parts in California, Japan and New Zealand. Part 2 of Eurocode 8 (CEN, 2005a) is quite
advanced from the point of view of the state-of-the-art and of seismic protection technology,
not only compared with the pre-existing status at national levels but also with respect to the
other parts of the new European seismic design standard (EN Eurocode 8) that address other
types of civil engineering works. It is up to the European community of seismic design
practice to make good use of it, to the benefit of the seismic protection of new bridges in
Europe and of its own professional competiveness in other seismic parts of the world. This
Designers’ Guide aspires to help this community become familiar with Part 2 of Eurocode 8,
get themost outof it and applyit in a cost-effective way.
1.2. Scope of Eurocode 8
Eurocode 8 covers the design and construction of earthquake-resistant buildings and other Clauses1.1.1(1),
civilengineering works– including bridges,but excludingnuclear power plants,offshorestruc- 1.1.1(2)[1]
tures and large dams. Its stated aim is to protect human life and property in the event of an Clause1.1.1(1)[2]
earthquake and to ensure that structures that are important for civil protection remain
operational.
Eurocode8hassixParts,listedinTable1.1.Amongthem,onlyPart2(CEN,2005a)iscoveredin Clauses1.1.1(4),
this Designers’ Guide. 1.1.3(1)[1]
1
Designers’GuidetoEurocode8:DesignofBridgesforEarthquakeResistance
Table1.1. Eurocode8parts
Part EN Title
1 EN1998-1:2004 Designofstructuresforearthquakeresistance.Generalrules,
seismicactions,rulesforbuildings
2 EN1998-2:2005 Designofstructuresforearthquakeresistance.Bridges
3 EN1998-3:2005 Designofstructuresforearthquakeresistance.Assessmentand
retrofittingofbuildings
4 EN1998-4:2006 Designofstructuresforearthquakeresistance.Silos,tanks,pipelines
5 EN1998-5:2004 Designofstructuresforearthquakeresistance.Foundations,
retainingstructures,geotechnicalaspects
6 EN1998-6:2005 Designofstructuresforearthquakeresistance.Towers,masts,chimneys
1.3. Scope of Eurocode 8 Part 2
Clauses1.1.1(2)– Part 2 of Eurocode 8 (CEN, 2005a) has as its sole object the seismic design of new bridges. It
1.1.1(4),1.1.1(6)[2] focuses on bridges having a deck superstructure supported directly on vertical or nearly
vertical concrete or steel piers and abutments. The seismic design of cable-stayed or arched
bridges is only partly covered, while that of suspension bridges, timber bridges (strictly
speaking, bridges on timber piers), masonry bridges, moveable bridges or floating bridges is
notcoveredatall.Part2ofEurocode8alsocoversthedesignofbridgeswithseismicisolation.
Unlike existing buildings, whose seismic assessment and retrofitting is covered in Eurocode 8
(CEN, 2005b), existing bridges arenot addressed at all.
1.4. Use of Eurocode 8 Part 2 with the other Eurocodes
Clauses1.1.2(1)– Part2 of Eurocode 8builds on the general provisions ofPart1 (CEN, 2004b) for:
1.1.2(3)[1]
g the general performancerequirements
g seismic action
g analysis methodsandprocedures applicableto all types of structures.
Clauses1.1(1),1.1(2) All thegeneral or specific provisions ofPart5 of Eurocode8 (CEN, 2004a) regarding:
[3]
g sitingof the works
g properties and seismic verification of thefoundation soil
g seismic design ofthe foundation or of earth-retaining structures
g seismic soil–structure interaction
apply aswell.
Clause1.2.1[1,2] Eurocode 8 is not a stand-alone code. It is applied alongside the other relevant Eurocodes in a
Clauses1.2.2,1.2.4[2] package referring to a specific type of civil engineering structure and construction material.
For bridges,there arefour Eurocode packages:
g 2/2: Concrete bridges
g 3/2: Steel bridges
g 4/2: Composite bridges
g 5/2: Timber bridges.
To be self-sufficient, each package includes all the Eurocode parts needed for design, as
follows:
g Several EN Eurocodes areincluded in every single bridge package:
– EN 1990:‘Basisof structural design’ (includingAnnexA2: ‘Application for bridges’)
– EN 1991-1-1: ‘Actions on structures – General actions – Densities,Self weightand
Imposedloadsfor buildings’
– EN 1991-1-3: ‘Actions on structures – General actions – Snow loads’
2
Chapter1. Introductionandscope
– EN 1991-1-4: ‘Actions on structures –General actions– Wind actions’
– EN 1991-1-5: ‘Actions on structures –General actions– Thermal actions’
– EN 1991-1-6: ‘Actions on structures –General actions– Actionsduring execution’
– EN 1991-1-7: ‘Actions on structures –General actions– Accidental actions’
– EN 1991-2:‘Actions on structures – Traffic loads on bridges’
– EN 1997-1:‘Geotechnical Design –General rules’
– EN 1997-2:‘Geotechnical Design –Ground investigation andtesting’
– EN 1998-1:‘Design of structures forearthquake resistance – General rules, seismic
actions,rules for buildings’
– EN 1998-2:‘Design of structures forearthquake resistance – Bridges’
– EN 1998-5:‘Design of structures forearthquake resistance – Foundations, retaining
structures,geotechnicalaspects’.
g Additional EN-Eurocodesare included in theConcrete Bridges package (2/2):
– EN 1992-1-1: ‘Design ofconcrete structures – General– General rules and rules for
buildings’
– EN 1992-2:‘Design of concrete structures –Concrete bridges – Design and detailing
rules’.
g Additional EN-Eurocodesincluded in the Steel Bridges package (3/2):
– EN 1993-1-1: ‘Design ofsteel structures – General rules and rules forbuildings’
– EN 1993-1-5: ‘Design ofsteel structures – Plated structural elements’
– EN 1993-1-7: ‘Design ofsteel structures – Strength and stabilityof planar plated
structures subject to out ofplane loading’
– EN 1993-1-8: ‘Design ofsteel structures – Design ofjoints’
– EN 1993-1-9: ‘Design ofsteel structures – Fatigue’
– EN 1993-1-10: ‘Design ofsteel structures – Selection ofsteel for fracture toughnessand
through-thicknessproperties’
– EN 1993-1-11: ‘Design ofsteel structures – Design ofstructures withtension
components’
– EN 1993-2:‘Design of steel structures –Steel bridges’.
g EN-Eurocodeswhich areincluded in addition inthe Composite Bridges package (4/2) are:
– EN 1992-1-1: ‘Design ofconcrete structures – General– General rules and rules for
buildings’
– EN 1992-2:‘Design of concrete structures –Concrete bridges – Design and detailing
rules’
– EN 1993-1-1: ‘Design ofsteel structures –General rules andrules forbuildings’
– EN 1993-1-5: ‘Design ofsteel structures – Plated structural elements’
– EN 1993-1-7: ‘Design ofsteel structures – Strength and stabilityof planar plated
structures subject to out ofplane loading’
– EN 1993-1-8: ‘Design ofsteel structures – Design ofjoints’
– EN 1993-1-9: ‘Design ofsteel structures – Fatigue’
– EN 1993-1-10: ‘Design ofsteel structures – Selection ofsteel for fracture toughnessand
through-thicknessproperties’
– EN 1993-1-11: ‘Design ofsteel structures – Design ofstructures withtension
components’
– EN 1993-2:‘Design of steel structures –Steel bridges’
– EN 1994-1-1: ‘Design ofcompositesteel and concrete structures – Generalrules and
rules for buildings’
– EN 1994-2:‘Design of compositesteel and concrete structures – Generalrules and rules
forbridges’.
Althoughpackage5/2,fortimberbridges,doesincludeParts1,2and5ofEurocode8,EN1998-
2:2005 itself isnot meant tocovertimberbridges.
1.5. Additional European standards to be used with EN 1998-2:2005
Part 2 ofEurocode 8 makes specific reference tothe following product standards: Clause1.2.4[2]
g EN 15129:2009: ‘Antiseismic Devices’
g EN 1337-2:2000: ‘Structural bearings– Part 2:Sliding elements’
g EN 1337-3:2005: ‘Structural bearings– Part 3:Elastomeric bearings’.
3
Designers’GuidetoEurocode8:DesignofBridgesforEarthquakeResistance
AlthoughEN1337-5‘Structuralbearings–Part5:Potbearings’isnotspecificallyreferenced,itis
also to be used, asrelevant.
1.6. Assumptions
Clauses1.3(1),1.3(2) Eurocode8referstoEN1990(CEN,2002)forgeneralassumptions,soreferenceismadehereto
[1,2] Designers’GuidestootherEurocodesforelaboration.Also,Eurocode8addstheconditionthat
nochangetothestructure(notevenonethatincreasestheforceresistanceofmembers)should
takeplace during execution or afterwardswithoutproperjustification and verification.
1.7. Distinction between principles and application rules
Clause1.4[1,2] Eurocode 8 refers to EN 1990 for the distinction between principles and application rules.
Accordingly, reference is made here also to Designers’ Guides to other Eurocodes for elabor-
ation. It is noted, though, that, in practice, the distinction between principles and application
rules is immaterial, as all provisions of the normative text are mandatory: non-conformity to a
single application rule disqualifies the entire design from being considered to accord with the
EN Eurocodes.
1.8. Terms and definitions – symbols
Clauses1.5,1.6[2] Terms and symbols are defined in the various chapters of this Designers’ Guide wherever they
first appear.
REFERENCES
CEN (Comite´ Europe´en de Normalisation) (2002) EN 1990: Eurocode – Basis of structural design
(includingAnnexA2:Applicationtobridges).CEN,Brussels.
CEN(2004a)EN1998-5:2004Eurocode8–Designofstructuresforearthquakeresistance–Part5:
Foundations,retainingstructures,geotechnicalaspects.CEN,Brussels.
CEN(2004b)EN1998-1:2004.Eurocode8–Designofstructuresforearthquakeresistance–Part1:
Generalrules,seismicactionsandrulesforbuildings.CEN,Brussels.
CEN(2005a)EN1998-2:2005Eurocode8–Designofstructuresforearthquakeresistance–Part2:
Bridges.CEN,Brussels.
CEN(2005b)EN1998-3:2005Eurocode8–Designofstructuresforearthquakeresistance–Part3:
Assessmentandretrofittingofbuildings.CEN,Brussels.
4
Designers’GuidetoEurocode8:DesignofBridgesforEarthquakeResistance
ISBN978-0-7277-5735-7
ICEPublishing:Allrightsreserved
http://dx.doi.org/10.1680/dber.57357.005
Chapter 2
Performance requirements and
compliance criteria
2.1. Performance-based seismic design of bridges
Paraphrasing – fortheparticular purposeof theseismic design of bridges – the fib 2010 Model
Codeib,2012)–theseismicperformanceofabridgereferstoitsbehaviourunderseismicaction:
the bridge must be designed, constructed and maintained so that it adequately and in an econ-
omically reasonable way performs in earthquakes that may take place during its construction
and service.Morespecifically, the bridge must:
g remain fit forthe use forwhichit hasbeen designed
g withstand extreme, occasionaland frequentseismic actionslikely to occur during its
anticipated use and avoid damage by an exceptionalearthquake to an extent
disproportionate to thetriggeringevent
g contributepositively to theneedsof humankindwithregard to nature, society,economy
and wellbeing.
Accordingly, three categories of performance are addressed by the fib 2010 Model Code
(fib, 2012):
g Serviceability:the ability of the bridge andits structural components toperform, with
appropriatelevelsof reliability, adequately fornormal useafter oreven duringseismic
actionsexpected during its service life.
g Structural safety: theabilityof thebridge and its structural components to guarantee the
overallstability, adequatedeformability and ultimateload-bearing resistance,
corresponding to occasional, extremeor exceptional seismic actions with appropriatelevels
ofreliability for thespecifiedreference periods.
g Sustainability: the ability of the bridge to contributepositively to the fulfilment ofthe
present needsof humankindwithrespect tonature, society and people, without
compromising the ability offuture generationsto meet their needsin a similar manner.
Inperformance-baseddesign,thebridgeisdesignedtoperforminarequiredmannerduringits
entirelifecycle,withperformanceevaluatedbyverifyingitsbehaviouragainstspecifiedrequire-
ments,basedinturnonstakeholders’demandsforthebridgeperformanceandrequiredservice
life. Performance-based design of a new bridge is completed when it has been shown that the
performancerequirementsaresatisfiedforallrelevantaspectsofperformancerelatedtoservice-
ability, structural safety and sustainability. If the performance of a structure or a structural
componentis considered tobe inadequate, we say we have‘failure’.
The Eurocodes introduce limit states to carry out performance-based design for serviceability
andsafety(CEN,2002).Limitstatesmarktheboundarybetweendesiredandundesirablestruc-
turalperformanceofthewholestructureoracomponent:beyondalimitstate,oneormoreper-
formancerequirementsarenolongermet.Fortheparticularcaseofseismicdesign,limitstates
are defined conceptually for all transient situations in the service life or the execution of the
bridgeduringwhichtheearthquakeactsincombinationwithanyrelevantpersistentortransient
actionsorenvironmentalinfluences.Theycorrespondtodiscreterepresentationsofthestructural
response under a specified exposure for which specific losses/damages can be associated. In
practice,they use simplified models for theexposure and thestructural response(fib, 2012).
5