毕业翻译英文稿.docx
- 文档编号:10575033
- 上传时间:2023-02-21
- 格式:DOCX
- 页数:25
- 大小:65.34KB
毕业翻译英文稿.docx
《毕业翻译英文稿.docx》由会员分享,可在线阅读,更多相关《毕业翻译英文稿.docx(25页珍藏版)》请在冰豆网上搜索。
毕业翻译英文稿
AdvancedLife-cycleAnalysisofExistingConcreteBridges
Abstract:
Acomplexinterdisciplinaryapproachtothereliabilityassessmentofreinforcedconcretestructureisintroducedanddemonstratedonarealexistingbridgestructure.thereliability,indexofthestructuredecreasesduringitslifecycleduetomaterialdegradation.Aretrofittingtothedesiredreliabilitylevelshouldbeperformed.Thisprocedureismodeledbyadvancedlife-cyclecomputersimulation.Themainfeatureofthepresentedapproachisthenonlinearfinite-elementanalysisofthestructureemployedfortherealisticassessmentofstructuralbehavior.Asuitabletechniqueofstatisticalsampling,whichallowsarelativelysmallnumberofsimulations,isusedinthiscontext.
Analyticaldeteriorationmodelscombinedwithinsitumonitoringareusedtolaunchthedegradationprocess.Thepresuentedmethodologyforadvancedlife-cycleanalysisisintegratedintheinnovativedecision-makingtoolthatsupportsmaintenanceplanningofengineeringstructures.
DOI:
10.1061/(ASCE)0899-1561(2008)20:
1(9)
CEDatabasesubjectheadings:
Structuralreliability;Probability;Concretestructures;Nonlinearanalysis;Servicelife;Lifecycles;Bridges;concrete.
Life-cyclereliabilityassessmentisrequiredfortheadministrationoftransportinfrastructurenetworkoperators.Decision-makingtoolsareusedtointerceptthedegradationandretrofittingprocessinordertosupportthemaintenanceofengineeringstructures(Frangopol2000),whichcanbepresentedasshowninFig.1.NumerousapproacheslikeBayesianupdating,MonteCarlosimulation,andassetmanagementusingthemultinationalgeneticalgorithm(Furutaetal.2004)havebeenusedforlife-cyclecostanalysis.Particularmethodologiesfortheusedofprobabilistic-basedassessmentareavailableandhavebeenproventoworkinpractice.
Nevertheless,inordertoperformacomplete,realisticlife-cycleanalysis,awidespectrumofmethodsshouldbeusedandcombined.ItmustincludenonlinearFEMmodeling,statisticalandreliabilitytechniques,anddegradationphenomenamodeling.Duetothecomplexityofthisproblem,aninterdisciplinaryapproachisrequiredthatshouldalsobeaccomplishedbyahealthmonitoringsystem.Sincethestochasticmodelsbehindtheproceduresareratherdemandingandtimeconsuming,mostoftheapproachesarecommonlybasedonsimplifiedmechanicalmodelsorformulas.
Theapproachusedinthiscontributiondiffersfromthepreviouslymentionedapproachesmainlybytheuseofnonlinearmodelsdescribingtherealstructure.Ofinterestisthestructuralreliability,whichisvalidatedbyaneasilyunderstandableconcept,wherethestochasticallyobtainedstructuralresistanceiscomparedwithexpectedloaddistributions.Thestochasticstructuralresistanceresponserequiresrepeatedanalysesofthestructurewithrandominputparameterstoreflectrandomnessanduncertaintiesintheinputvalues.Anonlinearcomputersimulationhastobeutilizedfortherealisticpredictionofstructuralresponseandthestructure'sresistance.Finalresultsinclude:
Statistical
characteristicsofresponse(stresses,deflections,crackwidth,etc.),informationondominatingandnondominatingvariables(sensitivityanalysis)andestimationofreliabilityandtheoreticalfailureprobability.Duetothefactthatnonlinearstructuralanalysisiscomputationallyverydemanding,asuitabletechniqueofstatisticalsamplinghastobeusedinordertoallowarelativelysmallnumberofsimulations.Newand/orupdated(significantlyimproved)theoreticalstatisticalandreliabilitymethods,whichhadtobedeveloped,verified,andimplementedtoaccomplishthisclaim,canbeitemizedasfollows:
●Small-samplesimulationofLatinhypercubesamplingforboth
randomvariablesaadrandomfields;
●Statisticalcorrelationusingthesimulatedannealingapproach
(VorechovskyandNovak2003);
●Smallnumberofrandomvariablestorepresentrandomfields
basedonthespectraldecompositionofthecovariancematrix;
and
●Sensitivityanalysisbasedonnonparametricrank-orderstatisticalcorrelation.
Themultipurposeprobability-basedsoftwareforstatistical
sensitivityandreliabilityanalysisofengineeringproblems
FREET(Novaketal.2003)isbasedonthetechniquesdescribed
above.ItwascombinedwiththenonlinearFEMtechniquesto
Fig.1.Maintenance-retrofittingprocesses
reducethecomputationaleffortofthepresentedapproach.Theapproachfurthermorepermitsadirectlinkbetweennonlineardegradationmodelsandnonlinearmaterialbehavioratthe“mesoscale."Theoverallgoalofthisapproachismorerealisticmodelingofthestructuralbehavior,andconsequentlyofthehealthindex(e.g.,efficientrealisticnonlinearmodelingofstructures),seeFig.2.Allthebasicconceptsmentionedaboveareappliedtoanexistinghighwayconcretebridge,the"ColleIsarcoViaduct,"introducedinthefollowingchapters.
StructuralAnalysis
Nonlinearfinite-elementanalysis,usedfortheidealizationand
processingofthehighwayconcretebridge,representsawell-
establishedmethodologyforfailureanalysisofcivilengineering
structuresinthedeterministicsense.Structuralconcreteisacomplexmaterialwithstronglynonlinearresponseevenunderservice
loadconditions.Therefore,thebehaviorofreinforcedconcrete
structureshastobeanalyzedbymeansofcorrespondinglyadvancedtechnology,takingintoaccountalltheimportantmaterialpropertiesandfeatures:
Tensilecracking,compressiveconfinement,reinforcement,includingitsbondtoconcrete,etc.Oneofthemostappropriatemethodologiesforarealisticfailureanalysisofcomplexheavyreinforcedandprestressedconcretestructureslikebridgesseemstobethesmearedmechanicsapproach.Themainfeaturesofsmearedmodelingofreinforcedconcretecanbeoutlinedasfollows:
●Damagemechanics,nonlinearfracturemechanics,enhanced
plasticity;
●Softeninginbothtensionandcompression;
●Smearedcrackapproach,crackbandmethod;and
●Discreteandsmearedreinforcement,bond-sliprelationship.
Forthedeterministicmodelingofthehighwayconcretebridge
"ColleIsarcoViaduct;"thenonlinearfinite-elementsoftware
ATENAwasused,whichimplementstheabove-mentionedfeatures.
图2
Fig.2.Essentialcomponentsforrealisticstructureassessment
Itisatoolwidelyusedinpracticeforrealisticcomputersimulationsandpredictionsofdamageandfailureofconcreteandreinforcedconcretestructures(Cervenkaetal.2005).
Besidetheimplementedadvancednonlineartechnologies(eg.,realisticnonlinearconstitutivemodels),furtherbenefitsofthistoolincludetraceabilityofthestructuralresponseunderloadingandenvironmentalactionstothepointofstructuralfailureanditsvariousinputoptions.Itenablesustocalculatetherealisticstructuralbehaviorunderserviceload[serviceabilitylimitstates(SLSs)]aswellastheloadcarryingcapacityofthestructure[ultimatelimitstates(ULSs)].Furthermore,thisappliance
allowstheinitiationofdeterministicconcreteproperties(characteristicvalues,varietyofadjustableparameters)accordingtothecompressivestrength,thedefinitionofthegeometryofthestructureinaCAD-likegraphicalenvironmentsupportedbyautomaticmeshgenerators,andtheimplementationofdiscretereinforcementbarsorprestressingcablesfullyindependentlyonthebasicfinite-elementmesh.Thefinallydiscretizedmodelcanbesubjectedtoappropriateboundaryconditionsandvariousactions:
Bodyforces,shrinkage,prestressing,nodalorlinearforces,prescribeddeformations,andtemperature.Theloadingactionshave
tobeappliedintheformofincrementalsteps.Theincrementalstepsareiterativelysolvedusingadvancedsolutionmethods(modifiedNewton-Raphson,arc-lengthorline-searchmethods),maintainingenergeticconvergencecriteria.Observationpointsor"monitoringpoints"freelyarrangedatthemodel,serveforrecordingtheevolutionofdeflections,forces,reactions,stresses,strains,crackgrowth,etc.,whichareconsequentlythebasicelementsforareliabilityanalysis.Theload-deflectionresponseaswellasthecrackgrowthandthecrackpatterncanbetracedalreadyduringanalysis.
Eachcompletednonlinearanalysisofamodelprovidesinthe
monitoringpointssinglerealizationsconcerningthestructuralresponse,thestress-strainstate(ateachincrementaccessible),andtheultimateload,whichisrequiredforstatisticalassessment.
DegradationModeling
Deteriorationcanbedescribedthroughavarietyofanalyticalmodels,whosemaindifferenceliesintheircomplexityandinthenumberofinputparametersnecessary.Modelsdescribingthecarbonationprocessofconcrete,aswellaschlorideingressandcorrosionofmildandprestressedsteels,areavailableinPapadakisetal.(1992),fibModelCode2005.Inthefirststep,thesemainlylocalorientedconceptsonaphysicalbasiswereintendedtobeincludedinthelife-cycleapproach.Sincetheimplementationofthisnonlinearconsiderationtoalargestructurewasexpensive(computational,dataascertainmentinnature),thedegradation
modelingoftheexampleathandwasperformedwithasimplified
time-to-failuremeasurement.
Foraconstantfailurerate,theexponentialdistributionisoftenusedasamodeloftime-to-failuremeasurements.Forengineeringstructures,wherethefailureratevariasovertime,theWeibulldistributionincombinationwithreliabilityassessmentsatparticulartimepointsissuitablefordegradationstatementsand,inconsequence,lifetimestatements.TheWeibulldistributionisdefinedas:
Ax)=rlbx(xib)}0-nxel-araha,f.osr<},b>o,a>o;公式
whereb=scaleparameter;c=shapeparameter,ande=ba
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 毕业 翻译 英文