桥梁评测_桥梁工程.pdf

BRIDGERATINGUSINGSYSTEMRELIABILITYASSESSMENTIIIMPROVEMENTSTOBRIDGERATINGPRACTICESNAIYUWANG,MASCE1BRUCERELLINGWOOD,DISTMASCE2ANDABDULHAMIDZUREICK,MASCE3ABSTRACTTHECURRENTBRIDGERATINGPROCESSDESCRIBEDINAASHTOMANUALFORBRIDGEEVALUATION,FIRSTEDITIONPERMITSRATINGSTOBEDETERMINEDBYALLOWABLESTRESS,LOADFACTOR,ORLOADANDRESISTANCEFACTORMETHODSTHESETHREERATINGMETHODSMAYLEADTODIFFERENTRATEDCAPACITIESANDPOSTINGLIMITSFORTHESAMEBRIDGE,ASITUATIONTHATHASSERIOUSIMPLICATIONSWITHREGARDTOPUBLICSAFETYANDTHEECONOMICWELLBEINGOFCOMMUNITIESTHATMAYBEAFFECTEDBYBRIDGEPOSTINGSORCLOSURESTHISPAPERISTHESECONDOFTWOPAPERSTHATSUMMARIZEARESEARCHPROGRAMTODEVELOPIMPROVEMENTSTOTHEBRIDGERATINGPROCESSBYUSINGSTRUCTURALRELIABILITYMETHODSTHEFIRSTPAPERPROVIDEDBACKGROUNDONTHERESEARCHPROGRAMANDSUMMARIZEDACOORDINATEDPROGRAMOFLOADTESTINGANDANALYSISTOSUPPORTTHERELIABILITYASSESSMENTLEADINGTOTHERECOMMENDEDIMPROVEMENTSTHISSECONDPAPERPRESENTSTHERELIABILITYBASISFORTHERECOMMENDEDLOADRATING,DEVELOPSMETHODSTHATCLOSELYCOUPLETHERATINGPROCESSTOTHERESULTSOFINSITUINSPECTIONANDEVALUATION,ANDRECOMMENDSSPECIFICIMPROVEMENTSTOCURRENTBRIDGERATINGMETHODSINAFORMATTHATISCONSISTENTWITHTHELOADANDRESISTANCEFACTORRATINGLRFROPTIONINTHEAASHTOMANUALFORBRIDGEEVALUATIONDOI101061/ASCEBE1943559200001712011AMERICANSOCIETYOFCIVILENGINEERSCEDATABASESUBJECTHEADINGSCONCRETEBRIDGESREINFORCEDCONCRETEPRESTRESSEDCONCRETELOADFACTORSRELIABILITYSTEELRATINGSAUTHORKEYWORDSBRIDGESRATINGCONCRETEREINFORCEDCONCRETEPRESTRESSEDCONDITIONASSESSMENTLOADSFORCESRELIABILITYSTEELSTRUCTURALENGINEERINGINTRODUCTIONTHEAASHTOMANUALFORBRIDGEEVALUATIONMBE,FIRSTEDITIONAASHTO2008ALLOWSBRIDGERATINGSTOBEDETERMINEDTHROUGHTHETRADITIONALALLOWABLESTRESSRATINGASRORLOADFACTORRATINGLFRMETHODSORBYTHEMORERECENTLOADANDRESISTANCEFACTORRATINGLRFRMETHOD,WHICHISCONSISTENTWITHTHEAASHTOLRFDBRIDGEDESIGNSPECIFICATIONS2007THESETHREERATINGMETHODSMAYLEADTODIFFERENTRATEDCAPACITIESANDPOSTEDLIMITSFORTHESAMEBRIDGENCHRP2001WANGETAL2009,ASITUATIONTHATCANNOTBEJUSTIFIEDFROMAPROFESSIONALENGINEERINGVIEWPOINTANDHASIMPLICATIONSFORTHESAFETYANDECONOMICWELLBEINGOFTHOSEAFFECTEDBYBRIDGEPOSTINGSORCLOSURESTOADDRESSTHISISSUE,THEGEORGIAINSTITUTEOFTECHNOLOGYHASCONDUCTEDAMULTIYEARRESEARCHPROGRAMAIMEDATMAKINGIMPROVEMENTSTOTHEPROCESSBYWHICHTHECONDITIONOFEXISTINGBRIDGESTRUCTURESINGEORGIAAREASSESSEDTHEENDPRODUCTOFTHISRESEARCHPROGRAMISSETOFRECOMMENDEDGUIDELINESFORTHEEVALUATIONOFEXISTINGBRIDGESELLINGWOODETAL2009THESEGUIDELINESAREESTABLISHEDBYACOORDINATEDPROGRAMOFLOADTESTINGANDADVANCEDFINITEELEMENTMODELING,WHICHHAVEBEENINTEGRATEDWITHINASTRUCTURALRELIABILITYFRAMEWORKTODETERMINEPRACTICALBRIDGERATINGMETHODSTHATARECONSISTENTWITHTHOSEUSEDTODEVELOPTHEAASHTOLRFDBRIDGEDESIGNSPECIFICATIONSAASHTO2007ITISBELIEVEDTHATBRIDGECONSTRUCTIONANDRATINGPRACTICESARESIMILARENOUGHINOTHERNONSEISMICAREASTOMAKETHEINFERENCES,CONCLUSIONS,ANDRECOMMENDATIONSVALIDFORLARGEREGIONSINTHECENTRALANDEASTERNUNITEDSTATESCEUSTHERECENTIMPLEMENTATIONOFLRFDANDITSCOMPANIONRATINGMETHOD,LRFR,BOTHOFWHICHHAVEBEENSUPPORTEDBYSTRUCTURALRELIABILITYMETHODS,ENABLEBRIDGEDESIGNANDCONDITIONASSESSMENTTOBEPLACEDONAMORERATIONALBASISNOTWITHSTANDINGTHESEADVANCES,IMPROVEDTECHNIQUESFOREVALUATINGTHEBRIDGEINITSINSITUCONDITIONWOULDMINIMIZETHELIKELIHOODOFUNNECESSARYPOSTINGFOREXAMPLE,MATERIALSTRENGTHSINSITUMAYBEVASTLYDIFFERENTFROMTHESTANDARDIZEDORNOMINALVALUESASSUMEDINDESIGNANDCURRENTRATINGPRACTICESATTRIBUTABLETOSTRENGTHGAINOFCONCRETEONONEHANDANDDETERIORATIONATTRIBUTABLETOAGGRESSIVEATTACKFROMPHYSICALORCHEMICALMECHANISMSONTHEOTHERSATISFACTORYPERFORMANCEOFAWELLMAINTAINEDBRIDGEOVERAPERIODOFYEARSOFSERVICEPROVIDESADDITIONALINFORMATIONNOTAVAILABLEATTHEDESIGNSTAGETHATMIGHTBETAKENINTOACCOUNTINMAKINGDECISIONSREGARDINGPOSTINGORUPGRADINGINVESTIGATINGBRIDGESYSTEMRELIABILITYRATHERTHANSOLELYRELYINGONCOMPONENTBASEDRATINGMETHODSMAYALSOBEOFSIGNIFICANTBENEFITPROPERCONSIDERATIONOFTHESEFACTORSISLIKELYTOCONTRIBUTETOAMOREREALISTICCAPACITYRATINGOFEXISTINGBRIDGESTHISPAPERISTHESECONDOFTWOCOMPANIONPAPERSTHATPROVIDETHETECHNICALBASESFORPROPOSEDIMPROVEMENTSTOTHECURRENTLRFRPRACTICETHEFIRSTPAPERWANGETAL2011SUMMARIZEDTHECURRENTBRIDGERATINGPROCESSANDPRACTICESINTHEUNITEDSTATES,ANDPRESENTEDTHERESULTSOFACOORDINATEDBRIDGETESTINGANDANALYSISPROGRAMCONDUCTEDTOSUPPORTREVISIONSTOTHECURRENTRATINGPROCEDURESTHISPAPERDESCRIBESTHERELIABILITYANALYSISFRAMEWORKTHATPROVIDESTHEBASISFORRECOMMENDEDIMPROVEMENTSTOTHEMBEANDRECOMMENDSSPECIFICIMPROVEMENTSTOTHEMBETHATADDRESSTHEPRECEDINGFACTORS1SENIORSTRUCTURALENGINEER,SIMPSON,GUMPERTZ,ANDHEGER,INC,41SEYONST,WALTHAM,MA02453FORMERLY,GRADUATERESEARCHASSISTANT,SCHOOLOFCIVILANDENVIRONMENTALENGINEERING,GEORGIAINSTITUTEOFTECHNOLOGY2PROFESSOR,SCHOOLOFCIVILANDENVIRONMENTALENGINEERING,GEORGIAINSTITUTEOFTECHNOLOGY,790ATLANTICDR,ATLANTA,GA303320355CORRESPONDINGAUTHOREMAILELLINGWOODGATECHEDU3PROFESSOR,SCHOOLOFCIVILANDENVIRONMENTALENGINEERING,GEORGIAINSTITUTEOFTECHNOLOGY,790ATLANTICDR,ATLANTA,GA303320355NOTETHISMANUSCRIPTWASSUBMITTEDONMARCH19,2010APPROVEDONAUGUST2,2010PUBLISHEDONLINEONOCTOBER14,2011DISCUSSIONPERIODOPENUNTILAPRIL1,2012SEPARATEDISCUSSIONSMUSTBESUBMITTEDFORINDIVIDUALPAPERSTHISPAPERISPARTOFTHEJOURNALOFBRIDGEENGINEERING,VOL16,NO6,NOVEMBER1,2011ASCE,ISSN10840702/2011/6863871/2500JOURNALOFBRIDGEENGINEERINGASCE/NOVEMBER/DECEMBER2011/863DOWNLOADED21MAR2012TO1809522453REDISTRIBUTIONSUBJECTTOASCELICENSEORCOPYRIGHTVISITHTTP/WWWASCELIBRARYORGRELIABILITYBASESFORBRIDGELOADRATINGBRIDGEDESIGN,ASCODIFIEDINTHEAASHTOLRFDSPECIFICATIONS2007,ISESTABLISHEDBYMODERNPRINCIPLESOFSTRUCTURALRELIABILITYANALYSISTHEPROCESSBYWHICHEXISTINGBRIDGESARERATEDMUSTBECONSISTENTWITHTHOSEPRINCIPLESUNCERTAINTIESINTHEPERFORMANCEOFANEXISTINGBRIDGEARISEFROMVARIATIONSINLOADS,MATERIALSTRENGTHPROPERTIES,DIMENSIONS,NATURALANDARTIFICIALHAZARDS,INSUFFICIENTKNOWLEDGE,ANDHUMANERRORSINDESIGNANDCONSTRUCTIONELLINGWOODETAL1982GALAMBOSETAL1982NOWAK1999PROBABILITYBASEDLIMITSTATESDESIGN/EVALUATIONCONCEPTSPROVIDEARATIONALANDPOWERFULTHEORETICALBASISFORHANDLINGTHESEUNCERTAINTIESINBRIDGEEVALUATIONTHELIMITSTATESFORBRIDGEDESIGNANDEVALUATIONCANBEDEFINEDINTHEGENERALFORMGX01WHEREXX1X2X3XNLOADANDRESISTANCERANDOMVARIABLESONTHEBASISOFBRIDGEPERFORMANCEOBJECTIVES,THESELIMITSTATESMAYRELATETOSTRENGTHFORPUBLICSAFETYORTOEXCESSIVEDEFORMATION,CRACKING,WEAROFTHETRAFFICSURFACE,OROTHERSOURCESOFFUNCTIONALIMPAIRMENTASTATEOFUNSATISFACTORYPERFORMANCEISDEFINED,BYCONVENTION,WHENGX0THUS,THEPROBABILITYOFFAILURECANBEESTIMATEDASPFPGX0C138ZFXXDX2WHEREFXXJOINTDENSITYFUNCTIONOFXANDFAILUREDOMAININWHICHGX0INMODERNFIRSTORDERFORELIABILITYANALYSISMELCHERS1999,EQ2ISOFTENAPPROXIMATEDBYPFC03WHERESTANDARDNORMALDISTRIBUTIONFUNCTIONANDRELIABILITYINDEXFORWELLBEHAVEDLIMITSTATES,EQ3USUALLYISANEXCELLENTAPPROXIMATIONTOEQ2,ANDANDPFCANBEUSEDINTERCHANGEABLYASRELIABILITYMEASURESELLINGWOOD2000WHENTHEFAILURESURFACEINEQ1ISCOMPLEXORWHENTHERELIABILITYOFASTRUCTURALSYSTEM,INWHICHTHESTRUCTURALBEHAVIORISMODELEDTHROUGHFINITEELEMENTANALYSIS,ISOFINTEREST,EQ2CANBEEVALUATEDEFFICIENTLYBYMONTECARLOMCSIMULATIONTHEAASHTOLRFDBRIDGEDESIGNSPECIFICATIONS2007AREESTABLISHEDONFORELIABILITYANALYSIS,APPLIEDTOINDIVIDUALGIRDERSNOWAK1999KIMANDNOWAK1997TABSHANDNOWAK1991WITHTHESUPPORTINGPROBABILISTICMODELINGOFRESISTANCEANDLOADTERMSNOWAK1993BARTLETTANDMCGREGOR1996MOSESANDVERMA1987,ANEXAMINATIONOFEXISTINGBRIDGEDESIGNPRACTICESLEDTOATARGETRELIABILITYINDEX,EQUALTO35BASEDONA75YEARSERVICEPERIODNOWAK1999,MOSES2001CONSISTENTWITHSUCHRELIABILITYBASEDPERFORMANCEOBJECTIVE,THEAASHTOLRFDSPECIFICATIONSSTIPULATETHATINTHEDESIGNOFNEWBRIDGES125D15DA175LIRN4WHEREDDEADLOADEXCLUDINGWEIGHTOFTHEWEARINGSURFACEDAWEIGHTOFTHEWEARINGSURFACEASPHALTLIREPRESENTSLIVELOADINCLUDINGIMPACTRNDESIGNSTRENGTH,INWHICHRNNOMINALRESISTANCEANDRESISTANCEFACTORWHICHDEPENDSONTHEPARTICULARLIMITSTATEOFINTERESTTHISEQUATIONISFAMILIARTOMOSTDESIGNERSWHENTHERELIABILITYOFANEXISTINGBRIDGEISCONSIDERED,ALLOWANCESHOULDBEMADEFORTHESPECIFICKNOWLEDGEREGARDINGITSSTRUCTURALDETAILSANDPASTPERFORMANCEFIELDINSPECTIONDATA,LOADTESTING,MATERIALTESTS,ORTRAFFICSURVEYS,IFAVAILABLE,CANBEUTILIZEDTOMODIFYTHEPROBABILITYDISTRIBUTIONSDESCRIBINGTHESTRUCTURALBEHAVIORANDRESPONSEINEQ2THEMETRICFORACCEPTABLEPERFORMANCEISOBTAINEDBYMODIFYINGEQ2TOREFLECTTHEADDITIONALINFORMATIONGATHEREDPFPGX0JHC138PT5WHEREHREPRESENTSWHATISLEARNEDFROMPREVIOUSSUCCESSFULPERFORMANCE,INSERVICEINSPECTION,ANDSUPPORTINGINSITUTESTING,IFANYTHETARGETPROBABILITY,PT,SHOULDDEPENDONTHEECONOMICSOFREHABILITATION/REPAIR,CONSEQUENCESOFFUTUREOUTAGES,ANDTHEBRIDGERATINGSOUGHTINTHEAASHTOLRFRMETHOD2007,THETARGETFORDESIGNLEVELCHECKINGBYUSINGHL93LOADMODELATINVENTORYLEVELIS35,WHICHISCOMPARABLETOTHERELIABILITYFORNEWBRIDGES,WHEREASTHETARGETFORHL93OPERATINGLEVELANDFORLEGAL,ANDPERMITLOADSISREDUCEDTO25OWINGTOTHEREDUCEDLOADMODELANDREDUCEDEXPOSUREPERIOD5YEARSMOSES2001THEPRESENCEOFHINEQ5ISACONCEPTUALDEPARTUREFROMEQS2AND3,WHICHPROVIDETHEBASISFORLRFDFOREXAMPLE,TRAFFICDEMANDSONBRIDGESLOCATEDINDIFFERENTPLACESINTHEHIGHWAYSYSTEMMAYBEDIFFERENTTOTAKETHISSITUATIONINTOACCOUNT,LRFRINTRODUCESASETOFLIVELOADFACTORSFORTHELEGALLOADRATING,WHICHDEPENDONTHEINSITUTRAFFICDESCRIBEDBYTHEAVERAGEDAILYTRUCKTRAFFICADTTFURTHERMORE,THECOMPONENTNOMINALRESISTANCEINLRFRISFACTOREDBYASYSTEMFACTORSANDAMEMBERCONDITIONFACTORCINADDITIONTOTHEBASICRESISTANCEFACTORFORAPARTICULARCOMPONENTLIMITSTATETHESYSTEMFACTORDEPENDSONTHEPERCEIVEDREDUNDANCYLEVELOFAGIVENBRIDGEINITSRATING,WHEREASTHECONDITIONFACTORISTOACCOUNTFORTHEBRIDGESSITESPECIFICDETERIORATIONCONDITION,ANDPURPORTSTOINCLUDETHEADDITIONALUNCERTAINTYBECAUSEOFANYDETERIORATIONTHATMAYBEPRESENTTHEBASISFORTHELRFRTABULATEDVALUESFORCWILLBEFURTHEREXAMINEDLATERINTHISPAPERTHELRFROPTIONINTHEAASHTOMBEEXTENDSTHELIMITSTATEDESIGNPHILOSOPHYTOTHEBRIDGEEVALUATIONPROCESSINANATTEMPTTOACHIEVEAUNIFORMTARGETLEVELOFSAFETYFOREXISTINGHIGHWAYBRIDGESYSTEMSHOWEVER,THEUNCERTAINTYMODELSOFLOADANDRESISTANCEEMBEDDEDINTHELRFRRATINGFORMATREPRESENTTYPICALVALUESFORALARGEPOPULATIONOFBRIDGESINVOLVINGDIFFERENTMATERIALS,CONSTRUCTIONPRACTICES,ANDSITESPECIFICTRAFFICCONDITIONSALTHOUGHTHELRFRLIVELOADMODELHASBEENMODIFIEDFORSOMEOFTHESPECIFICCASESASDISCUSSEDPREVIOUSLY,THEBRIDGERESISTANCEMODELSHOULDALSOBE“CUSTOMIZED”FORANINDIVIDUALBRIDGEBYINCORPORATINGAVAILABLESITESPECIFICKNOWLEDGETOREFLEC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