A review ofloading conditions for railway track st

STRUCTURALCONTROLANDHEALTHMONITORINGStruct.ControlHealthMonit.2008;15:207–234Publishedonline1October2007inWileyInterScience()DOI:10.1002/stc.227REVIEWProgressinStructuralEngineeringandMaterials:StructuralSafetyandReliabilityAreviewofloadingconditionsforrailwaytrackstructuresduetotrainandtrackverticalinteractionAlexM.Remennikov}andSakdiratKaewunruen*,y,zSchoolofCivil,Mining,andEnvironmentalEngineering,FacultyofEngineering,TheUniversityofWollongong,Wollongong,NSW2522,AustraliaSUMMARYTrainandtrackinteractionsduringservicesnormallygeneratesubstantialforcesonrailwaytracks.Suchforcesaretransientbynatureandofrelativelylargemagnitudeandarereferredtoasimpactloading.Therehasbeennocomprehensivereviewofthetypicalcharacteristicsoftheloadingconditionsforrailwaytrackstructures,inparticular,impactloadsduetothewheel/railinteraction,publishedintheliterature.Thispaperpresentsareviewofbasicdesignconceptsforrailwaytracks,abnormalitiesontracks,andavarietyoftypicaldynamicimpactloadingsimpartedbywheel/railinteractionandirregularities.Thecharacteristicsoftypicalimpactloadsduetowheelandrailirregularities,e.g.railcorrugation,wheelflatsandshells,wornwheelandrailprofiles,badweldsorjoints,andtrackimperfections,arepresentedwithparticularemphasisonthetypicalshapesoftheimpactloadwaveformsgenerallyfoundonrailwaytracks.Copyright#2007JohnWiley&Sons,Ltd.KEYWORDS:impactloading;railwaytrack;wheel–railinteraction;wheelandrailirregularities1.INTRODUCTIONRailwaytracksarebuilttotransporteitherpassengersormerchandisesacrossareas.Thetrackstructuresareexpectedtoguideandfacilitatethesafe,economic,andsmoothpassagesofany*Correspondenceto:SakdiratKaewunruen,SchoolofCivil,Mining,andEnvironmentalEngineering,FacultyofEngineering,TheUniversityofWollongong,Wollongong,NSW2522,Australia.yE-mail:[e-mail].}SeniorLecturerinStructuralEngineering.Contract/grantsponsor:AustralianCooperativeResearchCentreforRailwayEngineeringandTechnologies;contract/grantnumber:5/23Received23October2006Revised17July2007Accepted11August2007Copyright#2007JohnWiley&Sons,Ltd.rollingstocks.Analysisanddesignofrailwaytrackstructuresconsiderstaticanddynamicloadsactingonthetrackstructuresbecauseexcessiveloadingmayinducedamagetothetrackcomponentssuchasrail,railpad,sleeper,fasteningsystem,andfoundation.Figure1portraysatypicalconfigurationofaballastedrailwaytrack.Itscomponentscanbesubdividedintotwomaingroups:superstructureandsubstructure.Themostobviouscomponentsofthetracksuchastherails,railpads,concretesleepers,andfasteningsystemsformagroupthatisreferredtoasthesuperstructure.Thesubstructureisassociatedwithageotechnicalsystemconsistingofballast,sub-ballast,andsubgrade(formation).Bothsuperstructureandsubstructureareequallyimportantinensuringthesafetyandcomfortofpassengersandthequalityrideofthepassengerandfreighttrains.Railsarelongitudinalsteelmembersplacedontheequallyspacedsleepers.Therailsarethecriticalcomponentinguidingtherollingstocks.Theirstrengthandstiffnessmustbeampletomaintainasteadyshapeandthesmoothtrackconfiguration,andtoresistvariousforcesexertedbytravellingrollingstocks.Amainfunctionoftherailsistoaccommodateandtransferthewheel/axleloadsonthetracktothesupportingsleepers.Itsadditionalfunctionsinmodernrailtrackincludethattherail,whichconductssignalcurrents,alsoservesasanelectricalconductoronanelectrifiedline.Theprimarycomponentsofthefasteningsystemsarethemechanicalfastenersandtherailpads.Thefastenerswithstandthevertical,lateral,andlongitudinalforcesandoverturningmovementsofthetrackinadditiontokeepingtherailsinpositiononthesleepers.Theyalsotransferforcescausedbywheels,thermalchange,andnaturalhazardfromrailstotheadjacentsleepers.Railpads,whichareplacedontherailseat,areveryessentialtofilterandtransferthedynamicforcesfromtherailsandfasteningstothesleepers.Thehighdampingcoefficientoftherailpadsconsiderablyreducestheexcessivehigh-frequencyforcecomponents.Also,thepadsprovideresiliencytorail–sleeperinteraction,resultinginthealleviationofrailseatcrackingandcontactattrition.Sleepersaretransversebeamsrestingonballastandsupport.Inthepast,woodensleepershadbeenemployedastimbercouldbeeasilyfoundinthelocalarea.However,duetothehigherdurabilityandlongerservicelifespanofconcreteandsteelmaterials,theprestressedconcretesleepersand,toalimitedextent,steelsleepershavebeenadoptedworldwideinmodernrailwayFigure1.Atypicalrailwaytrackconfiguration.A.M.REMENNIKOVANDS.KAEWUNRUEN208Copyright#2007JohnWiley&Sons,Ltd.Struct.ControlHealthMonit.2008;15:207–234DOI:10.1002/stctracks.Thesleepersareutilizedto(1)uniformlytransferanddistributeloadsfromtherailfoottotheunderlyingballastbed;(2)sustainandretaintherailsatthepropergaugebykeepinganchoragefortherailfasteningsystem;(3)preserverailinclination;and(4)providesupportforrailbyrestraininglongitudinal,lateral,andverticalrailmovements.Ballastisafree-drainingcoarseaggregatelayerthatisusedastensionlesselasticsupportforrestingsleepers.Thislayeristypicallycomposedofcrushedstones,gravel,andcrushedgravelsuchasgraniteandbasalt,dependingonthelocalavail