extending the service life of civil structures -...

Based on the Workshop held in Amsterdam, the Netherlands 27 November 2014

Towards a Shared Innovation Programme

Extending the Service Life of

Civil Structures

T O W A R D S A S H A R E D I N N O V A T I O N P R O G R A M M E

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Table of contents

Acknowledgements iiiParticipants iv

1 Mostpromisingroutesforinnovation 11.1 Extendingtheservicelifeofcivilstructures 11.2 Ageingconcretestructures 11.3 Ageingsteelstructures 31.4 Callforaction 6

2 Introduction 72.1 TheIssue 72.2 TheProcess 72.3 Schedule 8

3 ChallengesofageingEuropeantransportinfrastructure 9

4 Concretestructures 114.1 Theexperts’viewpoint:challengesandvisions 114.1.1 Safetyofexistingstructures:linkingtheoryandpractice 114.1.2 FutureinFEMforconcretestructures 114.1.3 Innovativemethodsforthepreservationandretrofittingofexistingstructures 124.1.4 PresentandfuturechallengesofageingconcreteinfrastructureinNorway 134.2 Definingtheroutesandformulatingacommonagenda 144.2.1 Route1:Life-CycleAssessmentandcostingmethodology 154.2.2 Route2:Frameworkforre-assessmentofexistingstructures 154.2.3 Route3:Systembehaviour 17

5 Steelstructures 185.1 ExtendingtheservicelifeofsteelbridgesintheNetherlands 185.2 Practicalexperience,solutionsandresearchintosteelbridgesinGermany 195.3 Definingroutesandformulatingacommonagenda 205.3.1 Route1:InnovationsneededfortheFatigueroute 215.3.2 Route2:InnovationsneededfortheStaticstrengthroute 22

6 Callforaction 23

Appendices 24

ColophonThispublicationispartlybasedontheproceedingsoftheworkshop‘ExtendingtheServiceLifeofCivilStructures’,aninitiativeofTNO.

Referenceismadetoseveralpresentations.Ifyouareinterestedinthese,orwouldlikefurtherinformation,pleasecontactArieBleijenbergviaarie.bleijenberg@[email protected].

TNO.NL/ASSETMANAGEMENT


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Acknowledgements

On27November2014,expertsfromsevenEuropeancountries,representingtwentyorganisations,gatheredinAmsterdam,attheworkshop‘ExtendingtheServiceLifeofCivilStructures’.ThirtyparticipantscontributedtodiscussionsonmajorchallengesforageingcivilstructuresinEurope,andjoinedforcestodefinethemostpromisinginnovationroutesforextendingtheservicelifeofthestructures.

Firstofall,Iwouldliketothankallparticipants(seenextpage)forattendingthisinspiringeventandcontributingtheirexperience,expertiseandvisiontoformulateasharedvisiononextendingtheservicelifeofcivilstructures.

Thiswouldnothavebeenpossiblewithoutthethoughtfulpresentationsgivenby: Prof.WernerRothengatter(KarlsruheInstituteofTechnologyandadvisortothePällmann

CommissionandDaehreCommission)–Futureoftransportinfrastructurefinancing DavidAshurstCEngMICE(AssociateDirectorofARUP) FrankvanDoorenMSc(Rijkswaterstaat) HeinzFriedrichDipl.-Ing.(BASt) Prof.RobbyCaspeele(GhentUniversity) Prof.MaxHendriks(NorwegianUniversityofScienceandTechnology) PeterTanner,CivilEng.(EduardoTorrojaInstituteforConstructionScience–Spanish

NationalResearchCouncilandCESMAIngenieros) DrClausK.Larsen(NorwegianPublicRoadAdministration)

Thiseventwaspossiblethankstotheguidanceoftheday’schairmanArieBleijenbergMSc(TNO)andtoProf.JohanMaljaars(TNO),KimvanBuul-BesselingMSc(TNO)andProf.RaphaëlSteenbergen(TNO),wholedtheparallelsessions.IwouldalsoliketothankProf.RobPolder(TNO)forhissubstantivesupport,aswellasLauraHellebrandMSc(TNO)andDrMonicaNicoreac(TNO)fortheireffortinreportingontheworkshop.

JeroenKruithofMScDelft,30January2015

E X T E N D I N G T H E S E R V I C E L I F E O F C I V I L S T R U C T U R E S

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Participants

AdriVervuurt,TNOAgnieszkaBigajvanVliet,TNOAndražLegat,ZAGNationalBuildingandCivilEngineeringInstituteArieBleijenberg,TNODavidAshurst,ARUPDirkJanvanBoven,OverijsselProvincialAuthorityElenaReigAmoros,AccionaFrankvanDooren,RijkswaterstaatFransJonkman,UniversityofTwenteHeinzFriedrich,BAStJ.deBoer,DeBoerDCJeroenKruithof,TNOJohandenOuden,Joh.Mourik&CoHoldingBVJohanFleer,JansenVenneboerJohanMaljaars,TNOKeithHarwood,ARUPKimvanBuul-Besseling,TNOLauraHellebrandt,TNOLeoKlatter,RijkswaterstaatLouisCaers,BASFMarcelWillemse,Noord-HollandProvincialAuthorityMarkWehrung,BallastNedamBeheerMaxHendriks,NorwegianUniversityofScienceandTechnologyMonicaNicoreac,TNOPeterTanner,IETcc-CSICandCESMAIngenierosRichardWebers,BASFRaphaëlSteenbergen,TNORobPolder,TNORobbyCaspeele,GhentUniversitySalimYazici,Noord-HollandProvincialAuthoritySteffenFreitag,Ruhr-UniversitätBochumWernerRothengatter,KarlsruheInstituteofTechnology


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1 Most promising routes for innovation

1.1 Extending the service life of civil structures

ThroughoutEurope,structuressuchasbridgesandviaductsareapproachingtheendoftheirservicelife.Materialdegradationisadirectconsequenceofageingandleadstoreducedresistancetoenvironmentalimpacts.Inthemeantime,someoftheseenvironmentalimpacts,orloadsforshort,haveincreased.Trafficloadsandextremeweatherconditionssuchaswindloadsorwaveloadsarenotaspredictedinthe1960sor1970swhenasignificantproportionoftheexistinginfrastructurewasdesigned.Asaresult,thesafetyofstructuresisamatterforconcernandinseveralEuropeancountriestheywilleventuallyhavetoberenovatedorreplaced.However,replacementandrenovationarecostly,andcauseinconveniencetousers.

Duringtheworkshopwesawexamplesfrom: Germany,wheretheDaehreCommissiondetermineda€7.2billionannualre-investment

need(foralltransportinfrastructure)[A2]andanannualmaintenancebacklogof€2.65billion.

Norway,whichhasanannualmaintenancebacklogof€0.5-1billion[B4] TheNetherlands,withanexpectedannualreinvestmentneedforcivilstructuresof

€0.2-€0.5billion[A1].

Inthecomingdecades,extendingtheservicelifeofcivilstructureswillbethemajorchallengeinattemptstocutmaintenancecostsandreducenuisanceforroadusersalloverEurope.InordertoinitiatethedevelopmentofajointresearchagendaatEuropeanlevel,TNOorganisedaEuropeanworkshop,whichwasheldon27November2014.MorethanthirtyexpertsfromtwentyEuropeanorganisationsinsevenEuropeancountriesjointlyformulatedanswerstothefollowingquestions: Whatarethemostpromisingroutesforextendingtheservicelifeofcivilstructures? Whatarethetechnologies/innovationsneededinordertoputthemintopractice?

Themostpromisingrouteshavebeenformulatedseparatelyforconcreteandsteelstructures.

1.2 Ageing concrete structures

Twentyparticipantsfromvariousfields(academia,engineeringofficesandgovernmentalengineeringoffices)contributedtothissession,providingabroadscopeforformulatingproblemsaswellasdefiningroutesforinnovation.Thetopicscoveredfocusedbothonconcreteassetsinparticularandageingcivilstructuresingeneral(seealsoFigure1).


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Figure1.Promisingroutestoinnovationforageingconcretecivilstructures

1 Life-CycleCostingmethodologyFrom the point of view of the asset owner, technical problems and solutions should be translated into life-cycle costs. There is a need for quantitative, preferably monetised decision support for the management and maintenance of existing infrastructure. a. DevelopmentofanapplicableframeworkforLife-CycleCosting(LCC).b. Determiningthetime-dependentbehaviourofvariousmaintenancemeasuresandtheir

costaspects.c. Developmentofadecision-supporttool.d. Extensionofcostingmethodologytoenvironmentaleffects.

2 DevelopingpracticalcodifiedassessmentguidelinesforexistingstructuresIn order to assess and continuously guarantee the safety and availability of civil structure assets, practitioners require a framework, ultimately in the form of a norm, to deal with assessment and evaluation, as well as interventions.a. Determineguidelinesonwhattomeasureandmonitorandhow.b. Determinemethodsforincorporatingqualitativeinformationinaquantitativeway.c. Determinehowtousetheinformationgatheredtoupdateloadparameters,resistance

parametersandpartialfactorsinday-to-dayengineering.d. Developpracticalmodelsforresistanceofexistingstructures.e. Developsuitablereliabilitylevelsbasedoncostoptimisationandhumansafety

requirements.

Need for innovation

Asset owner

”How much does it cost?”

1 Life-CycleCosting

Engineer–practitioner

”How should I assess thesafety of existing structures?”

2 Codified assessment guidelines

Engineer–research

”How do I model the structure more realistically??”

3 Models:realfailure mechanisms& deterioration


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3 Advancedmodelsofstructures3.1 Modelling real failure mechanisms, avoiding hidden safeties in structural models There is a knowledge gap in the field of the behaviour of structures as a system, and the

impact of this behaviour on overall structural reliability.a.Howtodefineandassesssystemreliability,forductileorbrittlebehaviour. – Whatistheeffectoflocalbehaviouronglobalstructuralreliability? – Developdifferentacceptancecriteriaandsafetyformatforsystemandsectionlevels. – Developloadmodelsforsystemandsectionlevels. – Developacommonrationaleforassessingtherobustnessofexistingstructures.b.Performlarge-scaleteststocalibratethemodels,alsofordynamicloadings.c.Methodsandrequirementsfornon-destructivetesting,inordertodetermineproperties.d.Betterunderstandingofsoil-structureinteraction.e.DevelopmentofNon-LinearFiniteElementModelling(NLFEM)forexistingstructures

fordifferentfailuremechanics.f. DevelopmentofasafetyformatforNLFEMcalculations.g.Howtoassessmodeluncertainties.

3.2 Developing alternative structural models for deteriorating structures Theresistanceofanageingstructureisdependentontheconditionofthematerialsof

whichitiscomposed,forexamplethelevelofdegradationofreinforcementbars.However,thereislimitedknowledgeonhowandinwhatformtoincludematerialdegradationinstructuralmodels.a.Developprobabilisticmodelsforlocalandglobaldeterioration.b.Performsmall-andlarge-scaleexperimentsondeterioratingstructuralelements.c.Coupledeteriorationtoreliabilityassessmentoveracertain(remaining)lifetime.

1.3 Ageing steel structures

Duringtheworkingsessiononsteelstructures,theEuropeanexpertsdecidedonthemostpromisingroutesforextendingtheservicelifeofsteelbridges.TheroutesareshowninFigure2.Whatisnecessaryforbothroutesisadecision-makingtoolforassessingexistingbridgeswhichwillbeusefulfortheprocessofselectingthebridgesforre-assessmentanddecidingwhethertodonothing,torenovateortoreplace.Acoupleofaspectsneedtobedefinedasinputforthedecision-makingtool: Knowingtheconditionoftheassetsaspreciselyaspossible. Knowingthedifferentoptionsforstrengtheningtheassets.


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Thetechnologiesandinnovationsneededfortheroutessetoutaredescribedinthefollowingsections.

1. Fatiguestrength1.1 Loads and response (monitoring) Theprocessofmeasuringandmonitoringthestressesonrepresentativebridgescould

provideimportantdatathatcanbeusedforallthebridgesonahighway. Thefollowingtechnologiesarerequired:

a.Developaccessible,reliableandcompetitivemonitoringsystemswithalonglife.b.Developsensortechniquesthatareabletodetectevenminorfatiguedamage/

degradationinthestructureandgiveaccurateestimationsofthefatiguedegradationprocess(size,positionandgrowth).

c.Methodsforautomaticandstandarddataprocessing(ofthedataprovidedbythemonitoringsystems).

d.ProvidebetterestimationsoffatigueloadsandupdatethefatigueloadmodelfromEurocodewiththehelpofmeasureddata.

e.Writeaguidelineforengineersforextractingthestresses(hot-spotornominal)forfatigueforuseinthedesignstageofnewandexistingbridges.

f. Measurestoharmonisenationalstandardsforexistingstructures.g.Improvethepartialfactorsforfatiguegiveninthestandards,forexistingstructures,

forthetwocases:withandwithoutmonitoring/inspection.

Fatigue

Static strength

Loads

Loads

Response

Response

Strengthening

Strengthening

Replacement

Replacement

Monitoring

Monitoring

Figure2.Themostpromisingroutesforextendingtheservicelifeofsteelstructures


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1.2 Strengthening Regardingthestrengtheningofsteelbridgesforfatigue,therearetwolevelsforthe

proposedinnovationsandresearch:abroadlevelandamorefocusedone. Forthebroaderinnovations,betterexplorationofthefollowingaspectsisproposed:

a.Createnewrenovationtechniquesforsteelbridgesthatusesimpleandunsophisticatedon-sitetechnologies(low-techon-site)andhigh-techsolutionsinworkshops,asopposedtosolutionssuchasahigh-strengthconcreteoverlaypouredonsite.

b.Findnewwaystostrengthenmovablebridges.c. Lookintostrengtheningandrenovationtechniquesforthemaingirdersystem.

Onamorefocusedlevel,thefollowinginnovationsareneeded:a.Findandqualifythelifeenhancementofpost-weldtreatmentsonexistingstructures

anddeterminetheboundariesofapplicationb.Findnewweldingtechniquesfor‘oldsteels’c.Develop‘cold’(i.e.non-weld)repairtechniquesforshort,mediumandlong-term

structuredlifeextension.d.Findrepairtechniquesthatcanbecarriedoutwithongoingtraffic.

1.3 Replacement Regardingtheoptionofreplacingageingstructures,thereareplentyoflessonstobe

learnedfornewbridgesregardingnotonlythetechnicalaspectsbutalsobyplanningformonitoringandinspection.

Researchintothefollowingaspectsisproposed:a.Developbridge-renewaltechniqueswithfasterconstruction.b.Developbridge-renewaltechniquesthatcanbecarriedoutinextremelylimitedspaces.c.Betterregulaterobustnessofdesignsinstandards.

2. Staticstrength2.1 Loads and response monitoring Theresearchtopicsproposedinthisareacoveredseveralissues,including:

a.Exploretheoptionsandeffectsofregulationsonloadlimitationandtheenforcementoftheseregulationsusingmonitoringsystems.

b.ImprovetheloadmodelsfortheUltimateLimitState(ULS)byusingmeasuredtrafficloaddataonbridges(tobegenerallyusedandappliedinstandards).

c. Implementauniformmethodologyforextrapolatingmeasureddatatotargetprobabilitylevels(forbridge-specificuse).

2.2 Strengthening Forstrengtheningthestaticcapacityofsteelbridges,improvedmethodologies,manuals

andbettertechniquesshouldbelookedinto.Thefocusshouldbeonallassets,includingsmallerbridges.

2.3 Replacement Therobustbridgedesignforfuturetrafficloadsshouldberegulatedinnorms

(seeRoute1–Fatigue).


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1.4 Call for action

Maintainingareliableandsafe(transport)infrastructurenetworkistheconcernofeveryassetowner.Duringtheworkshopwesawthatthebudgetrequiredtomaintainthecurrentinfrastructurenetworkwillincreaserapidly.TheexamplesfromGermany,NorwayandtheNetherlandsareallproofofannualre-investmentneedsandmaintenancebacklogsofmanybillionsofeuros.

Theeffectivenessofthereplacementprogrammesisofconcerntoallcitizens,asisthesafetyofcivilstructures.WecallfornationalandEuropeanpolicy-makerstoexerttheirinfluenceonprogrammessuchasHorizon2020andInfravation,toencourageandsupportthebuildingandsharingofknowledgeonextendingtheservicelifeofcivilstructures.Duringtheworkshop,themainfocuspointsforengineeringwereidentified.Itisnowtimetotakeaction.Toreachanoptimuminboththeshortandthelongterm,knowledgeofexistingstructureshastobedeveloped,existingacademicknowledgeshouldbecontinuouslymadeavailabletopractitionersincodifiedformatand,atthesametime,existingandnewknowledgeonstructuresshouldbetranslatedinto(life-cycle)costaspects.

Thechallengeofdealingwithageinginfrastructurecannotbeaddressedinaneffective,efficientandsustainablewayonthelocalandnationallevelalone.WealsocalluponEuropeanknowledgeinstitutionstoacceleratethebuildingandsharingofacommonknowledgebaseinthefieldofexistingstructures.Existingworkinggroupsofplatformssuchasfib(InternationalFederationofStructuralConcrete)andRILEM(InternationalUnionofLaboratoriesandExpertsinConstructionMaterials,SystemsandStructures)provideaframeworkforworkingonseveralofthemosturgenttopics.

Theworkshopwasauniqueevent,whereexpertsfromalloverEuropejointlydraftedaresearchagendaforextendingtheservicelifeofcivilstructures.Letuscontinuetoworktogether,bydisseminatingthisagendaandusingitinourownorganisations.Togetherwecanchangethefuturebycarryingoutthisjointresearchagendatopreventafuturewithspirallingmaintenancecostsandconsiderablenuisanceforroadusers!


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2 Introduction

2.1 The Issue

ThroughoutEurope,structuressuchasbridgesandviaductsareapproachingtheendoftheirservicelife.Materialdegradationisadirectconsequenceofageingandleadstoreducedresistancetoenvironmentalimpacts.Inthemeantime,someoftheseenvironmentalimpacts,orloadsforshort,haveincreased.Trafficloadsandextremeweatherconditionssuchaswindloadsorwaveloadsarenotaspredictedinthe1960sor1970s,whenasignificantproportionoftheexistinginfrastructurewasdesigned.Asaresult,thesafetyofstructuresisofconcernandinseveralEuropeancountriestheywilleventuallyneedtoberenovatedorreplaced.However,replacementandrenovationarecostly,andcauseinconveniencetousers.

Inthecomingdecades,extendingtheservicelifeofcivilstructureswillbethemajorchallenge.InnovationswhichextendtheservicelifeofcivilstructureswillcutmaintenancecostsandreducenuisanceforroadusersalloverEurope.

WithaviewtosettingupajointresearchagendaatEuropeanlevel,TNOorganisedaninternationalworkshop,whichwasheldon27November2014.Here,morethanthirtyexpertsfromtwentyEuropeanorganisationsinsevenEuropeancountriesjointlyformulatedanswerstothefollowingquestions: Whatarethemostpromisingroutesforextendingtheservicelifeofcivilstructures? Whatarethetechnologies/innovationsneededinordertoputthemintopractice?

2.2 The Process

Thepurposeoftheworkshopwastofacilitatetheprocessoffindingjointanswerstothesequestions.Theschedulecanbeseenonthefollowingpage.

Theeventbeganwithaplenarysessionduringwhich,twokeynotespeakersaswellasthehosthighlightedtheurgencyofthechallengeposedbyageingcivil-structureassets.

Asfromatechnicalperspectivetypicalsteelandconcretestructureshavedifferentissues,twoseparateworkshopsprovidedaframeworkfordefiningtheroutesandtherequiredinnovations.Eachworkshopbeganwithshortpresentationsbyexpertsinthefield,whosharedtheirvisiononthemostpromisingroutesforservicelifeextensionaswellasthenecessarydevelopments.

Themainpartoftheworkshopswasdedicatedtoformulatinganswerstothequestionsabove.Inthesteelworkshop,aframeworkfortherouteswasproposedbythesessionleaderanddevelopedfurtherbythegroup.Intheworkshopforconcretestructures,foursub-groupsdiscussedanddefinedinnovationroutes(threepergroup).Therouteswerethenfurtherprioritisedbytheplenarygroup(andclusteredwherenecessary).Inthisprocessthequestion


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‘Whatarethemostpromisingroutesforextendingtheservicelifeofcivilstructures?’wasansweredbytheplenarygroup.Then,threemainprioritieswerechosenbythewholegroup.Thesewerefleshed-outinsmallergroups,withtheaimofansweringthequestion:‘Whatarethetechnologies/innovationsneededinordertoputthemintopractice?’

Afinalplenarysessionprovidedanopportunitytopresenttheproposedroutes,answerquestionsandgatherfeedback.

2.3 Schedule

10.00-10.45 Welcome Refer to10.45-11.00 Opening — ArieBleijenbergMSc,TNO A-111.00-12.30 Challenges of ageing European infrastructure — Prof.WernerRothengatter–KIT;advisortothePällmann A-2 CommissionandDaehreCommission(Futureoftransport infrastructurefinancing) — DavidAshurstCEngMICE–AssociateDirector,ARUP A-312.30-13.30 Lunch 13.30-16.30 Workshops on ageing structures Concrete structures LedbyProf.RaphaëlSteenbergen(TNO) — Prof.RobbyCaspeele(GhentUniversity):Safetyofexisting B-1 structures:linkingtheoryandpractice — Prof.MaxHendriks(NorwegianUniversityofScienceand B-2 Technology):FutureinFEMforconcretestructures — PeterTanner,CivilEng.(IETcc-CSICandCESMAIngenieros): B-3 Innovativemethodsforthepreservationandretrofittingof existingstructures — DrClausK.Larsen(NorwegianPublicRoadAdministration):Present B-4 andfuturechallengesofageingconcreteinfrastructureinNorway Steel structures LedbyProf.JohanMaljaars(TNO) — FrankvanDoorenMSc(Rijkswaterstaat):Experienceandfuture C-1 challengeswithexistingsteelcivilstructuresintheNetherlands — HeinzFriedrichDipl.-Ing.(BASt):Practicalexperience,solutions C-2 andresearchintosteelbridgesinGermany16.30-17.00 Conclusions – Sharing and feedback17.00-18.00 Reception

Thefollowingsectionssummarisethecontentoftheevent.ThepresentationscanbefoundintheAppendix.

T OWA R D S A S H A R E D I N N O V A T I O N P R O G R AMM E

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3 Challenges of ageing European transport infrastructure

Guaranteeingtheavailabilityandsafetyofaconstantlyageingagingarealofcivilstructuresismorethanalocalornationalproblem.Thiswasillustratedwithexamplesfromseveralcountries,presentedbythehostoftheeventandtwokeynotespeakers.

ArieBleijenbergMSc(TNO)gaveanoverviewofthesituationregardingageinginfrastructureintheNetherlands.[A1]Asignificantincreaseinthenumberofconstructionstoberefurbishedisnecessaryinthecomingdecades,implyingcostsofatleast€150million,upto€500milliononayearlybasis.Increasingtheservicelifeofexistingstructureswillhelptostayclosetolowercostmargin–savinghundredsofmillionsofeurosinthenationalbudget.Asanexample,byincreasingthemeanrepairlifefrom10to25years,thenumberofnecessarybridgereplacementsdecreasesbyapproximately40%in2020andbyanevenhigherproportioninthelaterdecades(Figure3).

Figure3.EstimatedincreaseinthenumberofstructuresinneedofrepaironDutchhighways.Source:Non-traditionalassessmentandmaintenancemethodsforagingconcretestructures–technicalandnon-technicalissues;R.B.Polderetal.–MaterialsandCorrosion2012,63,No.12.

Prof.WernerRothengatter(KarlsruheInstituteofTechnology)addressedtheissuesmainlyonthelevelofdecision-makingandplanningofinfrastructureinvestment.[A2]InGermany,significanteffortshavebeenmadetodescribethelifetimeofcivilstructures(components)instatisticalterms,whilethesemodelscanbefurtherimprovedbyalsotakingaccountofvisualinspectionsandtechnicaldepletion.

4000

3500

3000

2500

2000

1500

1000

500

Meanrepairlife10

Num

bero

fstruc

turest

hatn

eedrepa

ir

1990 2010 2030Year

2050 2070

Meanrepairlife25

0


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Besidesthephysicalmodelshowever,life-cycleplanningshouldaccountforfinancialaspects.Prof.WernerRothengattersuggeststhatresearchinthefieldofinvestmenttheoryandoperationsresearchiswelldefined.Inthemeantime,publicbudgetsdonotreflecttheneedsimposedbythelargenumberofageingstructures,therebycreatingasignificantmaintenancebacklog–€2.65billionperyearinGermanyalone(DaehreCommission,2012).ThePällmannCommission(2000),DaehreCommission(2012)andBodewigCommission(2013)haveworkedonadvisingdecision-makersondealingwithexistinginfrastructure.Theinclusionofphysicalandfinanciallife-cycleplanninginnewinfrastructureprojectswasoneofthekeyrecommendations.Thisapproachcanbesupportedby,amongothers,BIMmodellingofalllargeinfrastructureprojects,whichhasbeenrecommendedasalegalrequirementtopolicy-makersinGermany.

Inthemeantime,atEuropeanlevel,infrastructureinvestmentsfocusmainlyonnewconstruction.Ifsufficientexploitationormaintenancebudgetsarenotforeseen,thisinfrastructurewilldegraderapidly–forexamplethehigh-speedrailnetworkinSpain.Fromthisaspect,apositiveexampleofsuchlife-cycleapproachtoinfrastructureinvestmentswastherestrictivepolicyadaptedbytheCzechTransportMasterPlanning.TostrengthenthefinancialsituationofpublicworksProf.Rothengatteradvocatedforinclusionofprivatelymanagedorganisationsandtrustfunds.DavidAshurstCEngMICE,thesecondkey-notespeaker,addressedthesituationintheUnited Kingdom.[A3]Inthecomingfiveyears,thelargest-everinfrastructureinvestmentsareplannedforroadsandrailways,amountingto€80billion.Rothengatterpointedouttheneedsofinfrastructureassetowners:safety,adaptingtofuturerequirements,optimisingtheuseofexistingassets,understandingdeteriorationandminimisingdisruptiontooperation.Inthemeantime,technicalchallengeshavetobeaddressed,including:fatigueproblems,accurateinspectionandmonitoringtechniques,chloridedamage,ageingofpost-tensionedconcretebridges.AccordingtoMrAshurstCEngMICE,thefocuspointsofageingstructuresare:(1)Gettingtoknowassets,(2)Fatigueinsteelstructures,and(3)Chlorideingress.ThepresentationsindicatenotonlythattheageingoftheexistingcivilstructuresisaEurope-wideissue,butalsothatthechallengesarefoundinabroadrangeoffields,fromspecifictechnicalquestionstoinvestmentmodelsandpolicymaking.Thediscussionsthatfollowedfocusedontechnicalaspects,andpartlyaddressedlife-cyclecosting.


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4 Concrete structures

TheparallelsessionaboutageingconcretestructureswasledbyProf.RaphaëlSteenbergen(TNO).Twentyparticipantsfromvariousfields(academia,engineeringoffices,governmentalengineeringoffices)contributedtotheworkofthissession,providingabroadscopeforformulatingproblemsaswellasdefiningroutesforinnovation.Thepresentationsanddiscussionsaresummarisedinthefollowingsections.

4.1 The experts’ viewpoint: challenges and visions

4.1.1 Safetyofexistingstructures:linkingtheoryandpractice

Prof. Robby Caspeele (Ghent University) proposedsixmainchallengesaspromisingroutesfordevelopment: Developingpracticalcodifiedassessmentguidelinesforexistingstructures,basedon

aprobabilisticapproachandapplicableforpracticalusebyintroducedsafetyfactors. TheguidelinesshouldbecompatiblewiththeEurocodeframeworkandabletoaccountfor

alternativesafetylevels,remainingworkinglife,referenceperiodandadditionalinformation. Takingaccountofrealfailuremechanisms,spatialvariabilityincluding(time-dependent)

degradationandsystembehaviourwhenquantifyingstructuralreliability. Developingacommonrationaleforrobustnessassessmentofexistingstructures. Howtoincorporatequalitativeinformationfrominspectionsinaquantitativeway. Quantifyingtheinfluenceofdifferentassessmentmethodsonthestructuralreliabilitylevel. Dealingwiththeincreasedcomplexityintheassessmentofexistingstructures.‘Beyond

failureprobability’(Pf)takethecostaspectofriskintoaccountindecision-making(inamoreadvancedwaythaniscurrentlythecase).

4.1.2 FutureinFEMforconcretestructures

Prof. Max Hendriks (Norwegian University of Science and Technology & Technical University of Delft)focusedonNon-LinearFiniteElementModelling(NLFEM).NLFEMisaresource-intensivecomputationalmethodthatdescribesstructuralbehaviourwithhighaccuracy.Itmaybeacompetitiveanalysistechniqueincaseswheresignificantadditionalanalysiscostsareoutweighedbythesavingsmadeduetotheresultsofhigheraccuracy.

Thesafetyassessmentofexistingcivilstructuresmaybesuchacase.However,theoutputofNLFEMisadesignloadwithnoindicationofagivenexceedanceprobabilityandthus,implicitly,asafetylevel.Whenthetargetrequirementofstructuralsafetyisareliabilityindex/acceptedfailureprobability,theresultofNLFEMthereforedoesnotgiveadirectlyapplicableanswerastowhetherthestructureissufficientlysafe.Therefore,fortheapplicabilityofNLFEM,asafetyformatshouldbedeterminedandaccepted.


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4.1.3 Innovativemethodsforthepreservationandretrofittingofexisting structures

ThepresentationbyPeter Tanner, Civil Eng. (IETcc-CSIC and CESMA Ingenieros)focusedon: Risk-basedmodelsandrequirements Thefundamentalproblemrelatingtotheassessmentofexistingstructuresistofindan

answertothequestionastowhethertheyaresafeenoughforfutureuse.Decision-makingonstructuralsafetyusingtheapproachesadoptedineverydaypracticeisaffectedbyasetofshortcomings,sincerisksassociatedwithaspecificinfrastructurearenotexplicitlyquantified.Therefore,theallocationofresourcesforriskreductionisoftennotoptimal.Toolsandrationalrisk-acceptancecriteriaaretobedeveloped,intendedforthepracticalapplicationofexplicitriskanalysismethods.Theuseofsuchmethodsinstructuralassessmentaffordsaseriesofsignificantadvantages:—updatedinformationmaybetakenintoaccountfortheverificationofstructural

performance—systemreliabilitymaybeverified—benefitsfromriskreductionorcontrolmeasuresmaybequantified—rationaldecisioncriteriaareavailablefortheacceptanceofsufficientlysmallrisks—interventionsmaybeoptimised.

Step-by-stepexaminationimprovingaccuracyofdata Themaindifferencebetweenassessingperformanceinexistinganddesignphase

structuresisthatmanycharacteristicswhosevaluesaremerelyanticipatedinthelattercanbemeasuredintheformer.Aphasedprocedureisthereforenormallyusedforstructuralassessmentinwhichtheaccuracyofthemodelsisenhancedfromphasetophasebyimprovingexaminationassumptionsthroughupdatesoftheinitialgeneraldata.

Themostaccuratewaytoapplyactualsitedatawouldbetoconductaprobabilisticanalysis.However,suchmethodsmaynotbesuitedtoeverydayusebypractisingengineersandarelimitedtothefinalphaseofthestagedassessment,ifnecessary.Structuralsafetyverificationsintheprecedingphasesarebasedonasimilarpartialfactorformulationasadoptedinstructuraldesigncodes,inwhichtherepresentativevaluesforthevariablesandthepartialfactorscanbemodifiedonthebasisofupdatedinformation.

Toolsarethereforebeingdevelopedtoaccommodatesitedatabyupdatingboththecharacteristicvaluesofloadandstrengthvariablesaswellastheassociatedpartialfactors.Simplemodelsarealsoneededtoextendthesetools,originallyestablishedforsoundstructures,tothereliabilityassessmentofdeterioratingstructures.

Systemreliability Thepartialfactorformatsavailableincurrentcodeshavebeendevelopedforstructural

safetyverificationsatcross-sectionslevel.Forthispurpose,independentcalculationsarenormallyusedfortheestablishmentofinternalforcesandmomentsontheonehand,andthecorrespondingresistancesontheother.Accordingtosuchaprocedure,thecurrentpartialfactormethodsdonottakeintoaccounttheeffectofstructuralbehaviouronreliability.


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Instructureswithaductilebehaviour,redistributionsofinternalforcesandmomentsarepossibleandthefailureofonecross-sectiondoesnotleadtothecollapseofthesystem.Insuchcases,theprobabilityoffailureofthesystemiswellbelowtheprobabilityoffailureoftheindividualcross-sections.Systemratherthancross-sectionreliabilityshouldthereforebeconsideredintheassessmentofexistingstructures.Suchanapproachmayleadtoconsiderablebenefits,particularlyinthecaseofstructureswithaductilebehaviour.

Riskcontrolbymeansofmonitoring Differentcausesmayleadtothenon-complianceofaparticularrequirementrelatingtoan

existinginfrastructure.Manyofthecausesmaybetracedbacktodeviationsfromexpectedactionsorresistances.Thequantificationofparametersrelatingtosuchinfluencesmayprovideevidenceaboutthedegreeofcomplianceofagivenstructurewithaparticularserviceabilityorsafetyrequirement.Suchparametersmaythereforebecalledindicatorsandassociatedthresholdvaluescanbeestablishedonariskbasis,aswellasadmissibleaveragefrequenciesforoutcrossing.

Indicatorsmaybemonitoredandthemeasuredvaluescancontinuouslybecomparedtothethresholdvaluespreviouslyestablished.Alarmsystemsmaybeinstalledwhichareactivatedintheeventofoutcrossing.Safetymeasurescanthereforebeadopteddependingontheconsequencesoftheobservednon-compliance.Basedonsuchanapproach,andbyusingmoderninformationtechnology,inspectionsoflargeinfrastructuresmaybeautomatedandoptimised.

4.1.4 PresentandfuturechallengesofageingconcreteinfrastructureinNorway

Prof.RobPoldergaveapresentationthatwaspreparedbyDr Claus K. Larsen (Norwegian Public Road Administration),whowasunfortunatelyunabletoattend.Thepresentationcoveredthefollowingtopics: LargemaintenancebackloginNorway,(€0.5-€1billionp.a.)whichincreaseseveryyear. Themostrelevantdegradationmechanisms:

—Reinforcementcorrosion—Alkali-silicareaction(ASR)

Developmentsneededinthefieldofassessmentandinspection:—Evaluatingthetypeandqualityofdata—Providingcorrectandreliableassessments

Developingsupportfor‘choiceofaction’:—Developcriteriaforchoosingcorrecttypeofaction—Determinethe’servicelife’ofvariousactions—Developnew,reliableandcost-effectivesolutions

Understandhowdesigninfluencesservicelife.


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4.2 Defining the routes and formulating a common agenda

Thefinalaimoftheworkshopwastoformulate(1)alimitednumberofroutes,and(2)specificpointstotackle.Thiswasachievedbymeansofafacilitatedprocessinwhich,first,eachofthefourdiscussiongroups(thespeakersconstitutedaseparategroup),proposedthree‘mostpromisingroutes’ofdevelopment.Thesearesummarisedbelow(notprioritised): Life-cycleanalysisandcostingofmaintenancemethods. Methodsforassessingremainingservicelife. Monitoringofdifferentcriticalcross-sections. Baselineassessment–fastandcheapmethodforthemajorityofstructures;high-accuracy

methodologyforcriticalstructures. Quantifyingthebenefitsofintervention. Costestimateforresiduallife,usingmonitoringresults. Uniqueguidelineforstructuralreliability. Understandingthesystembehaviourofrepair,thegoalbeingtoincreasetheservicelifeof

repair. Systemapproachforassessmentofexistingstructures,spatialvariabilityuntilcollapse. Codifiedframeworkforassessingexistingstructures. Effectofdeteriorationonstructuralperformance–experimentsandmodels. BroaderapplicationareaofNLFEMmodelsforstructuralreliabilityassessment.

Apartfromtheroutes,therelevantinputduringthediscussionsincludedthefollowingcomments: ‘Oneofthemainchallengesistounderstandthecurrentstatusofthestructureonthe

conditioncurve.’ ‘Foralargenumberofassets,aquickscanmethodsuchasimageanalysisisapromising

techniquetosupportdecision-making.’ ‘Theperceptionofservicelifeshouldbeoncommongrounds,inordertospeakeffectively

aboutservice-lifeextension.’ ‘Fromthepointofviewoftheowner,technicalproblemsandsolutionsshouldbe

translatedintocostaspects.’

Thethreemostpromisingrouteswereproposedandthenecessarydevelopmentsforeachwerefleshed-outingroups.Theproposedroutesanddevelopmentsaredescribedinthefollowingsections.


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4.2.1 Route1:Life-CycleAssessmentandcostingmethodology

‘WithoutLife-CycleCostingmethod,nothingmakessense.’(foradecision-maker)Thistopichadbeennamedasaprioritybyamajorityofparticipants.Theneedforquantitative,preferablymonetisable,decisionsupportwasarticulatedinthegroupdiscussions.Infrastructureassetmanagerswantto: Determinetheremaininglifeofexistingstructures. Beabletodeterminethecostsrelatingtovariousstructuralupgradingandrenovation

measures. Basedonquantifiedinformationaboutthecurrentconditionsupportedbymeasurement

data,gainknowledgeaboutthetime-dependentimpactofrepairandtheremainingservicelife.

Optimisemaintenanceplanning.

Torealisethesegoals,life-cycleassessmentandcostingmethodologyshouldbedevelopedforpractice.Thiscanbetranslatedintothefollowingneeds:a. DevelopmentofanapplicableframeworkforLife-CycleCosting.b. Determiningthetime-dependentbehaviourofvariousmaintenancemeasuresandtheir

costaspects.c. Developmentofdecision-supporttool.d. Extendcostingmethodologytoenvironmentaleffects.

4.2.2 Route2:Frameworkforre-assessmentofexistingstructures

Somecommentsfromthediscussions: ‘Weneedaguidelinethatdoesn’tneednewresearch.Somethingfast,thatisbetterthan

whatwehavenow.’ ‘Inacademicresearchweassumethatinformationisavailable–butthisisnotthecasein

practice.’

Inseveraldiscussions,aswellasinthespeakers’presentations,theneedforadevelopedframeworktore-assessexistingstructureswasemphasised.Practitionersarecallingforaframework(ultimatelyintheformofacode)todealwithbothassessment/evaluationandinterventions.Afour-stepframeworkwasdevelopedbythediscussiongroup.ThestepsareshowninFigure4.


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Figure4.Frameworkforre-assessmentofexistingstructures

First,amethodologyfordatagatheringshouldbecodified.Inpractice,alargenumberofcivilstructures(e.g.bridges)mustbekeptsufficientlysafeandfulfilfunctionalrequirements.Thisrequires‘fastandcheap’methods,enablingtheassessmentofseveralstructuresandpossiblyincorporatingupdating.Thesecondstep,basedontheinitialdata,istheassessmentofthecurrentcondition.Inthethirdstep,basedontheresultsofasimpleassessmentofthecurrentcondition,thelevelofdetailingshouldbedetermined.Forstructuresinwhichsafetyisquestionable,highaccuracymethodsareneeded.Ontheonehandthisreferstothevalueofinformation(Whattomeasure?Howprecisely?)andontheotherhandtothedetailoftheanalysismethod(uptocomplexitysuchasusingnon-linearfiniteelementmethods).Thefourth,highlyrelevantsteptoadaptforpracticeistheincorporationoftime-dependenceinsafetyformats.Althoughimplicitlytakenintoaccountincertainloadingschemes(e.g.trafficloadonbridgesinthecodesintheNetherlands),thedevelopmentofstructuralsafetyintimeisnotdeterminedincurrentpractice.

Thesestepswillleadto(morerealistic)inputforcostoptimisation.Thisreferstotheultimategoalofinfrastructuremaintainersinthefieldofdecision-making.Thefollowingarespecificaimsforresearchrelatingtotheaboveframework:a. Determineguidelinesonwhattomeasureandmonitorandhow.b. Determinemethodsforincorporatingqualitativeinformationinaquantitativeway.c. Determinehowtousetheinformationgatheredtoupdateloadparameters,resistance

parametersandpartialfactorsinday-to-dayengineering.d. Developpracticalmodelsforresistanceofexistingstructures.e. Developsuitablereliabilitylevelsbasedoncostoptimisationandhumansafety

requirements.f. Developaframeworkforadjustablepartialfactors.

1 Datagathering

2 Assessmentofcurrentcondition

3 Determinelevelofdetailing

4 Safetyformatincorporatingtime

5 Costoptimisation


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4.2.3 Route3:Systembehaviour

Thethirdmainchallengewasarticulatedinseveralpresentationsandwaschosenasaprioritybyamajorityofparticipants.Thereseemstobeacommonunderstandingthatthereisaknowledgegapinthefieldofthebehaviourofstructuresasasystem,andtheimpactofthisbehaviouronoverallstructuralreliability.First,itisnotknown(inday-to-dayengineeringpractice)howtoevaluateexistingstructuresbasedontheir‘real’failuremechanisms:cross-sectionalcapacityisconsideredinsteadofsystemcapacity.Ontheotherhand,spatialvariability(mainlyofstrengthparameters)isnotfullyincorporatedinstructuralre-assessment.

Currentperformance-basedstructuralreliabilitycriteria(i.e.acceptedprobabilitiesoffailure)refertoonespecificelementorsinglecross-section,forexampleabeaminbending.Inrealityhowever,theremaybesomeredundanciesinthesystem,sincestructuresdifferinrobustness.Thisaspectisnotquantifiedandthereislittleknowledgeavailableonhowtorealisticallyassesstheoverallfailureprobability(thussafety)ofacivilstructure.Thefollowingnecessarytechnologiesshouldbedevelopedinordertoaddresstheknowledgegapinsystembehaviour:a. Howtodefineandassesssystemreliability,forductileorbrittlebehaviour.

—Whatistheeffectoflocalbehaviouronglobalstructuralreliability?—Developdifferentacceptancecriteriaandsafetyformatforthesystemandsectionlevels.—Developloadmodelsforthesystemandsectionlevels.—Developacommonrationaleforrobustnessassessmentofexistingstructures.

b. Performlarge-scaleteststocalibratethemodels.c. Methodsandrequirementsfornon-destructivetesting,inordertodetermineproperties.d. Betterunderstandingofsoil-structureinteraction.

Inordertomodelstructuresmorerealisticallyandtakemoreadvantageof‘hiddensafeties’,developmentsinthenon-linearfiniteelementanalysisarerequired.Theseare:e. DevelopmentofNLFEMmodelsforexistingstructuresfordifferentfailuremechanics.f. DevelopmentofasafetyformatforNLFEMcalculations.

Furthermore,materialdegradationmodelsshouldbebetterincorporatedintheanalysisofexistingstructures.Toachievethis,thefollowingstepsareimportant:g. Developprobabilisticmodelsforlocalandglobaldeterioration.h. Performsmall-andlarge-scaleexperimentsondeterioratingstructuralelements.i. Coupledeteriorationtoreliabilityassessmentinacertain(remaining)lifetime.


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5 Steel structures

TheparallelsessionaboutageingsteelstructureswasledbyProf.JohanMaljaarsfromTNO&EindhovenTechnicalUniversity(theNetherlands).Thetenparticipantsfromvariousfields(academia,engineeringoffices,governmentalengineeringoffices)gavetheirinputtothesession,settingtheframeworkfortheinnovationroutes.

Thepresentationsanddiscussionsaresummarisedinthefollowingsections.

5.1 Extending the service life of steel bridges in the Netherlands

Frank van Dooren MSc (Rijkwaterstaat, GPO department Bridges and Viaducts)presentedtwomaincriticalaspectsofageinginfrastructureintheNetherlands:localfatigueissuesinsteelbridgeswithorthotropicdecks,andstaticstrengthissuesinsteelbridges.

Forthetopicoffatigueinsteelbridges,alistoftopicsrequiringfurtherdevelopmentandresearchwasproposed: Safety-approachfatiguecalculations(γmf,γff):thepartialfactorsforfatigueinexisting

structuresgiveninstandardsneedtobeimproved. ImproveEurocode1993-1-9+1993-2:updateclassificationofbridgesandimproved

calculationdemands. ImproveEN1991-2:updatingthefatigueloadmodel4and5forexistingbridges,withthe

helpofmeasureddata. Improvethedemandsforextractinghot-spotornominalstressesfromFinalElements(FE)

forfatiguecalculations,atthedesignstage. Disseminatetheknowledgeofcrack-propagationcalculationswiththeprospectof

determiningsafeinspectionintervals. Developnewtechniquestoreducethestressesinorthotropicdecks. Improvedetection/measurementandpredictiontechniques(individualbridges). Giveattentiontoglobalfatigueinthemaingirdersystem.

Twopromisingdevelopmentswerereferredtointhispresentation:a. Bridgemonitoringwithreal-timeupdateforcrackextensionmodels.b. Virtualmonitoringconcept(researchprojectfundedbytheEuropeanCommission):

bridgemonitoringtechnologiesarebeingdevelopedtoprovethatmanybridgesaresafeandthattheservicelifecanbeextendedtothebenefitofmoresustainableroad-assetmanagement.


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ThetopicofstaticstrengthforsteelbridgesintheNetherlandsisrelatedtothelevelofconservatismoftheEurocodeinpredictingthestatictrafficloadsforexistingbridges.Thedevelopmentsrequiredinrelationtotheuncertaintyinthedefinitionofloadforexistingbridgesarelistedbelow: ExpandingthenumberofWeigh-In-Motion(WIM)locations(alsoonlocalroads)fora

betterdefinitionoftheloadsonexistingbridges. Expandinglong-termload-effectmeasurementsforabetter(local)definitionoftheloads

andloadeffectsonexistingbridges. Expandtheexistingbridgecodetomakeuseoftheaboveeffects. Develop‘enforcementmethods’,usingmonitoringsystems.

5.2 Practical experience, solutions and research into steel bridges in Germany

Heinz Friedrich Dipl.-Ing. (Federal Highway Research Institute, BASt)gaveapresentationaboutthepracticalexperiences,solutionsandresearchinGermanywithrespecttosteelbridges.Thereisawarenessoftheproblemofincreasedtrafficonoldbridges,butthesupporttoolsfordecidingwhethertoreplaceorrenovatearetoocomplextobeusedinday-to-daypractice.AnumberofproposalsweremadefortheReplacementoptioninthedecisiontree:a. Designandconstructbridgesforthefuture(predicted)traffic.b. Usefatigue-friendlydetails.c. Workwithtwosuperstructures.

TherelevantinnovationsfortheRenovationoptionarelistedbelow:d. UseofalayerofHighStrengthConcrete(HSC)onthedeckordevelopanother

economicallyandtechnicallyefficientsolutiontolowerthestressesinthedeck.e. Strengtheningtobedonefromthetop(lesscomplicated)andshouldbebeneficialforall

fatigue-pronedetails.f. Inallcases,newrenovationtechniquesshouldbeeitherhigh-techwhencarriedoutin

workshops,orlow-techon-site.g. Findnewweldingandrepairtechniqueswithongoingtraffic.h. Newweldingtechniquesandmaterialsareneededthatarecompatiblewitholdsteelin

existingbridges.i. Findthecauseofandsolutiontotheproblemofnewcracksoccurringinexistingbridges

whenanewasphaltlayerisadded(isitaproblemofnewcracksorexistinghiddencracks?).

RegardingthestaticstrengthofexistingsteelbridgesinGermany,theissueofmajorconcernistheinabilityofthemainstructuralsystemtotakeoverextraweightfromsteelfromfatigue-friendlyrepairs.Abetterdistributionofstressescanbeobtainedwithathickerasphaltlayer.


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5.3 Defining routes and formulating a common agenda

Thegoaloftheplenarysessionwastodecideonthemostpromisingroutesforextendingtheservicelifeofsteelbridgesandtodefinetheimportantinnovationstobedealtwith.

Themostpromisingroutesaredividedintotwoareas:fatigueandstaticstrengthofageingsteelbridges.Eachoftheareashasfouraspectsonwhichresearchanddevelopmentsshouldfocus.TheroutesareshowninFigure5.

Figure5.Schemeofthemostpromisingroutesforextendingtheservicelifeofsteelbridges

Acriticalaspectofthedecision-makingprocessistoknowtheconditionoftheassetsaspreciselyaspossible.Also,thedifferentoptionsthatareavailableforstrengtheningtheseassetsisanimportantaspectintheevaluationprocess.Adecision-makingtoolfortheassessmentofexistingbridgesthatincorporatestheaforementionedcriteriarepresentsacrucialdevelopmentforbothroutespresentedinFigure5.

Theinnovationsneededfortheroutesarepresentedinthefollowingsections.

Fatigue

Static strength

Loads

Loads

Response

Response

Strengthening

Strengthening

Replacement

Replacement

Monitoring

Monitoring


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5.3.1 Route1:InnovationsneededfortheFatigueroute

1. Loadsandresponse(monitoring)Measuringandmonitoringthestressesonrepresentativebridgeswasrecognisedasanimportanttoolwhichcouldproviderelevantdatatobeusedforallthebridgesonahighway.Thefollowingareneededforthis:a. Accessiblemonitoringsystemswithextendedlife.b. Standardisationofthedataanalysisandgeneralisationofthemeasuredstresses.c. Usethemeasureddatatoobtainbetterestimationsoffatigueloadsandtoupdatethe

fatigueloadmodelfromEurocode.d. Harmonisationoftheexistingstandardsandimprovementofthepartialfactors.

2. StrengtheningWithregardtostrengtheningsteelbridgesagainstfatigue,innovationsandresearchwereproposedontwolevels:abroadlevelandamorefocusedone.Forthebroaderinnovations,betterexplorationintothefollowingaspectswasproposed:e. Waysofstrengtheningmovablebridges.f. Developmentoflesshigh-techtechniquesforstrengthening.g. Lookingintothewaysofstrengtheningthemaingirdersystemforfatigueresistance.

Forthemorefocusedtechniquesandinnovationsneeded,themainpointsofinterestare:h. Othersolutionsofstrengtheningthedeck(e.g.usingacompositedeckplate).i. Developmentof‘cold’(i.e.no-weld)repairtechniquesforshort,mediumandlong-term

structuredlifeextension.j. Repairtechniquesdonewithongoingtraffic.k. Findandquantifytheeffectofpost-weldtreatmentonenhancingthelifeofexisting

structures.

3. ReplacementWithregardtothereplacementofageingstructures,itwasmentionedthatthereareplentyoflessonstobelearnedfornewbridges,relatingnotonlytothetechnicalaspectsbutalsotoplanningformonitoringandinspection.l. Researchshouldfocusonbridge-renewaltechniquescarriedoutinextremelylimitedspaces.m. Therobustnessofdesignshouldbebetterregulatedinnorms.


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5.3.2 Route2:InnovationsneededfortheStaticstrengthroute

1. LoadsandresponsemonitoringTheresearchtopicsproposedinthisareacoverseveralissues,including:a. Thelimitationofloadsandtheenforcementwiththehelpofmonitoringsystemsorby

settingclearregulationsregardingheavyaxlesallowedontheroads.b. ImprovedloadmodelsfortheUltimateLimitState(ULS)representsanotherpointoffocus

forthisroute:thiscouldbedonebyusingthemeasureddatafromWIMsystemstopredictULSloadsandbyimplementingauniformmethodologyofextrapolatingthestaticloadsincodes/norms/manuals.

2. StrengtheningWithregardtostrengtheningthestaticcapacityofsteelbridges,itisnecessarytolookintoimprovedmethodologiesandbettertechniques,anddevelopmanuals.Thefocusshouldbeonallassets,includingsmallerbridges.

3. ReplacementTherobustdesignofbridgesforfuturetrafficloadsshouldberegulatedinnorms(asforRoute1–Fatigue).


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6 Call for action

Maintainingareliableandsafe(transport)infrastructurenetworkistheconcernofeveryassetowner.Duringtheworkshopwesawthatthebudgetsrequiredtomaintainthecurrentinfra-structurenetworkwillincreasefast.TheexamplesfromGermany,NorwayandtheNetherlandsareallproofofannualre-investmentneedsandmaintenancebacklogsofmanybillionsofeuros.

Theeffectivenessofreplacementprogrammesisofconcerntoallcitizens,asisthesafetyofcivilstructures.WecalluponnationalandEuropeanpolicy-makerstoexerttheirinfluenceonprogrammessuchasHorizon2020andInfravation,toencourageandsupportthebuildingandsharingofknowledgeonextendingtheservicelifeofcivilstructures.Duringtheworkshop,themainfocuspointsforengineeringwereidentified.Itisnowtimetotakeaction.Toreachanoptimuminboththeshortandthelongterm,knowledgeofexistingstructureshastobedeveloped,existingacademicknowledgeshouldbecontinuouslymadeavailabletopractitionersincodifiedformatand,atthesametime,existingandnewknowledgeonstructuresshouldbetranslatedinto(life-cycle)costaspects.

Thechallengeofdealingwithageinginfrastructurecannotbeaddressedinaneffective,efficientandsustainablewayatthelocalandnationallevelsalone.WealsocalluponEuropeanknowledgeinstitutionstoacceleratethebuildingandsharingofacommonknowledgebaseinthefieldofexistingstructures.Existingworkinggroupsorplatformssuchasfib(InternationalFederationofStructuralConcrete)andRILEM(InternationalUnionofLaboratoriesandExpertsinConstructionMaterials,SystemsandStructures)provideaframeworkforworkingonseveralofthemosturgenttopics.

Theworkshopwasauniqueevent,duringwhichexpertsfromalloverEuropejointlyformulatedthefollowingmostpromisingroutes: Forconcretestructures,thefollowingdevelopmentsareneeded:

—Quantitative,preferablymonetiseddecisionsupportforthemanagementandmaintenanceofexistinginfrastructure.

—Practicalcodifiedassessmentguidelinesforexistingstructures.—Advancedmodelsofstructures: – Modellingrealfailuremechanisms,avoidinghiddensafetiesinstructuralmodels. – Developingalternativestructuralmodelsfordeterioratingstructures.

Forsteelstructures,thefollowinginnovationsareneededfortheFatigueandStaticStrengthroutes:—Loadsandresponse(monitoring).—Strengthening.—Replacement.

Letuscontinuetoworktogether,bydisseminatingthisagendaandusingitinourownorganisations.Togetherwecanchangethefuturebycarryingoutthisjointresearchagendatopreventafuturewithspirallingmaintenancecostsandconsiderablenuisanceforroadusers!


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Appendices

AppendixA:PlenarypresentationsA-1 ArieBleijenbergMSc(TNO)-Extendingservicelifeofcivilstructures:Welcome!A-2 Prof.WernerRothengatter–KITandadvisortothePällmannCommissionandDaehre

Commission(Futureoftransportinfrastructurefinancing)-ChallengesofAgeingEuropeanTransportInfrastructure

A-3 DavidAshurstCEngMICE–(AssociateDirector,ARUP)-ExistingUKBridgesInfrastructure

AppendixB:Parallelsessionpresentations:concretestructuresB-1 Prof.RobbyCaspeele(UniversityofGhent):Safetyofexistingstructures:linkingtheory

andpracticeB-2 Prof.MaxHendriks(NorwegianUniversityofScienceandTechnology):FutureinFEMfor

concretestructuresB-3 PeterTanner,CivilEng.(IETcc-CSICandCESMAIngenieros):Innovativemethodsforthe

preservationandretrofittingofexistingstructuresB-4 DrClausK.Larsen(NorwegianPublicRoadAdministration):Presentandfuture

challengesofagingconcreteinfrastructureinNorway

AppendixC:Parallelsessionpresentations:steelstructuresC-1 FrankvanDoorenMSc(Rijkswaterstaat):Experienceandfuturechallengeswithexisting

steelcivilstructuresintheNetherlandsC-2 HeinzFriedrichDipl.-Ing.(BASt):Practicalexperience,solutionsandresearchintosteel

bridgesinGermany

extending the service life of civil structures -...

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