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ImprovedServiceabilityCriteriaforSteelGirderBridgesMichaelG.Barker,Ph.D.,andKarlE.Barth,Ph.D.2A~bstract:CurrentAASHTO,LRFDBridgeDesignSpecificationsServiceIdeflectionlimitsareinplacewiththepurposetopreventdeformation-inducedstructuraldamageandpsychologicaluserdiscomfortfromexcessbridgevibration.Previousresearchhasshownthatde-flectioncriterionaloneisinsufficientincontrollingexcessbridgevibrationsandstructuraldeteriorationoftheconcretedeck.Previousresearchshowsthatnaturalfrequencycriteriabettercontrolsexcessvibrationthandeflectioncriteriaalone.Inaddition,previousresearchshowsnosig-nificantcorrelationbetweendeflectionandstructuraldeformationoftheconcretedeckslab.Tobettercontrolexcessbridgevibrationsanddeformation-inducedstructuraldeterioration,twonewseparatecriteriaformulationsareproposed.Thefirstformulationconsistsofanaturalfrequencycriteriatransformedintodeflection-typetermsfamiliartothetypicalbridgeengineer.Thesecondproposedformulationdirectlycon-trolstheactingflexuralstrainintheconcretedecktocontroldeformation-inducedstructuraldamage.Theproposedserviceabilitycriteriaareappliedtoadatabaseof185steelgirderbridges.Boththeas-builtbehaviorandthedesignoptimizedbehaviorareexaminedandcomparedwithcurrentAASHTOserviceabilitycriteria.Theproposedusercomfortanddeformation-induceddamageserviceabilityformulationsareintendedtobeincorporatedintoongoingFederalHighwayAdministrationandbridgeindustrylong-termbridgeperformanceresearchwhereservice-abilitycriteriaisanimportantcomponent.DOI:10.1061/(ASCE)BE.1943-5592.0000402.~2013AmericanSocieO,ofCivilEngineers.CEDatabasesubjectheadings:Girderbridges;Deflection;Vibration;Serviceability.Authorkevwords:Bridgedeflections;Bridgevibrations;Bridgeserviceability.IntroductionDeflectionlimitshavetheiroriginfromtheraih'oadindustryandwereanattempttolimitbridgevibrations.The1905AmericanRailroadAssociationlimitedthespan-to-depthratioasanindirectmethodoflimitingdeflections.Inthe1930s,theU.S.BureauofPublicRoadsperformedastudytodetermineadesignmethodthatwouldlimitexcessbridgevibration(Barthetal.2002).Thestudyincludedbridgescommonforthetimeperiodthatconsistedofwoodplankdeckswithasuperstructureofponyandpinconnectedtrussesandsimplebeambridges.Therewerenocompositebeamsandfewcontinuousspans.Ifthebuildingmaterialwassteel,ASTMA7steelwasthetypicalgrade.TheAmericanAssociationofStateHighwayOfficials(AASHO)deflectionlimitsfirstappearedin1941,partiallybecauseoftheresultsoftheBureanofPublicRoadsStudy(FountainandThunman1987).TheASCE(1958)investigatedtheoriginsfortheseserviceloaddeflectionrequirementsandreportedthatnoclearbasisforthelimitswasfound(Barthetal.2002).TheAASHTOLRFDSpecifications(2012)detailsgeneralde-signprinciples.Article2.5.2.6advisesthatthemaximumdefor-mationofthebridgeshouldnotexceedthe(spanlength)/800forgeneralvehicularbridgesandthe(spanlength)/l,000forvehicularbridgeswithpedestriantraffic.Thereasonforthesmallerallow-abledeflectionforpedestrianbridgesisthatpedestriansaremore1professor,CivilandArchitecturalEngineering,Univ.ofWyoming,Laramie,WY82070(correspondingauthor).E-mail:Barker@uwyo.edu2jackH.SamplesProfessor,CivilandEnvironmentalEngineering,WestVirginiaUniv,Morgantown,WV26506.Note.ThismanuscriptwassubmittedonFebruary2,2012;approvedonApril18,2012;publishedonlineonApril20,2012.DiscussionperiodopenuntilDecember1,2013;separatediscussionsmustbesubmittedforin-dividualpapers.ThispaperispartoftheJourna7ofBridgeEngineering,Vol.18,No.7,Julyt,2013.~ASCE,ISSN1084-0702/2013/7-673-677/$25.00.sensitivetobridgevibrationsthanvehicularpassengers.AASHTOsuggeststhattheserviceliveloaddoesnotexceedtheAASHTOtruckdesignloadingfordeterminingdeflections.Live-LoadDeflectionStudiesAcollectionofpreviousstudies(FountainandThunman1987;GoodpastureandGoodwin1971;NevelsandHixon1973)in-vestigatedtherelationshipbetweenservicedefolxnationsanddeckdeterioration.Thesestudiesdidnotfindanysignificantcorrelation.Acollectionofstudies(WalkerandWright1971;Aramraks1975;andDeWolfandKou1997)investigatedbridgevibrationbehavior.Humanresponsetovibrationsandtheeffectsthatvibrationhasonthecrackingoftheconcretedeckwereexamined.Thecon-clusionsofthesestudieswerethatlive-loaddeflectionsaloneareinsufficientincontrollingexcessivebridgevibration,andthatbridgevibrationbehaviorisinfluencedmorebythenaturalfrequencyofthebridge,vehiclespeed,andsurfaceroughness.Humanshavetwotypesofresponsetovibration.Thefirstisphysiological,whichoccurswhenfrequenciesofvibrationapproachresonancewiththenaturalfrequenciesofinternalorgans.Theseeffectscancausephysicaldiscomfort.Psychologicaldiscomfortgenerallyoccursfi'omunexpectedmotion,suchasapedestrianonabridgewithatruckapproaching.TheAISC(2003)detailshowanactivityapersonisperformingaffectspsychologicaldiscomfort.Thetypicalexampleisapersonsittinginanofficewhoisgoingtobemoresusceptibletovibrationsthanapersonwalkingonabusybridge.Thisisbecause,inanoisyenvironment,apersonismentallypreparedforvibrationscomparedwiththoseinaquietenvironment(Allenetal.1997).Thereisagrowingmovementinstructuralengineeringtomoveawayfromsimplelength/numb