高速铁路有轨道结构动态响应有限元建模与分析

高速铁路有轨道结构动态响应有限元建模与分析

根据我国新高速客运公线h-1号线的实际情况，以轨道结构为研究对象，进行了轨道结构的动态响应建模和轨道不均匀破坏的动态分析，计算了不同垫层的影响值，并分析了不同表面波的性能。包括新安装杆的振动特性、室内测量精度和杆的动态特性。研究轨道结构的动态特性。基于轨道纵向条带状分布的规则性结构,建立轨道元数值计算方法与轨道结构空间有限元模型。轨道元作为数学模型,从形式上表现为0.6m长轨枕间距的一段轨道截矩,涵盖一根轨枕及相应钢轨质量、扣件、垫层、道床及路基在内的动力学特性;应用列车前后适时“增加与缩减”1个或多个轨道元的方法,进行无限长轨道结构动态响应分析。理论计算与实测结果对比表明,所建有限元模型能够反映有砟轨道结构的振动特性。运用车辆—轨道耦合动力学理论和轨道元数值计算方法,研究不同速度与不平顺幅值下无缝线路焊接区迎轮错牙型不平顺对轮轨系统各部分动力性能的影响。列车高速运行时,焊缝不平、轨面剥离与擦伤等各种轨面短波不平顺均将显著增加轮轨相互作用,加速道砟破碎与道床路基不均匀沉降,恶化轨道几何状态,所以应及时消除该类脉冲激扰源的影响。既有线列车提速到200km·h-1时,轨道不平顺是引起轮轨动作用力的主要根源。通过确定各类不平顺幅值的控制范围,为提速线路制定轨道养护维修和不平顺管理标准提供依据。为完善轨道结构空间有限元分析,根据能量法和Timoshenko梁理论,运用振型叠加法建立轴向温度力作用下无缝线路钢轨谐响应有限元模型,研究不同温度力作用下与不同轨道结构参数影响下钢轨的振动特性,掌握其发展规律和变化特点。计算表明:随着轴向温度力(以拉为正)的增加,钢轨共振频率增大,而共振幅值呈非线性递减;在轴向受压温度力作用下,上述变化关系更显著;钢轨类型、轨枕支承间隔长度与轨下支承刚度将一定程度上影响无缝线路钢轨的共振频率。根据接触—冲击响应的虚位移原理,将轮轨接触边界条件用罚函数法释放,采用点面接触单元导出轮轨接触有限元控制方程,建立轨道结构落轴冲击动力有限元方程,计算高速铁路有砟轨道结构落轴冲击动态响应,分析采用轨下、枕下胶垫及道砟垫等不同隔振条件下轨道结构动力性能的变化。结果表明:轨下胶垫增加弹性后,可有效吸收车轮冲击荷载和减少轨枕、道床的振动;枕下粘贴弹性胶垫后,钢轨位移与轨枕振动加速度有所增加,而钢轨、道床的振动加速度与轨座反力有一定程度的降低,有利于缓和列车对轨枕产生的附加冲击动力,提高碎石道床稳定性;道床底部铺设道砟垫后,钢轨位移与道床振动加速度有所增加,钢轨振动加速度与轨座反力则有一定程度的降低,路基面所承受压力降低20%左右,在一定频率范围内提高了轨道结构对基础的隔振效果。因此,多层隔振系统应具体设计与合理配置,才能缓和其轮轨间剧烈的动力作用。运用轨道激振器与落轴冲击等实验手段,结合室内实尺轨道模型,形成包括改变轨枕类型、枕间距、扣件类型、轨下与枕下胶垫、道砟垫及道砟密实度等测试工况。通过变换激振器的激振频率与落轴高度模拟列车不同速度,测试多种工况下轮轨作用力、钢轨与轨枕的位移及振动加速度、轨座反力等动态响应。分析试验结果表明:轨下基础刚度较大,钢轨振动能量也较强;增加轨枕质量,在提高钢轨振动能量的同时,使得轨枕振动主频有所下降;采用枕下垫或道砟垫,增加了轨道结构整体弹性,降低了钢轨自振频率;设置辅助轨后,钢轨主振频率有所增加。测试信号功率谱和振动传递函数的计算表明:轨下垫层弹性增加,钢轨传递至轨枕的能量将减少;采用枕下胶垫后,由钢轨传递至轨枕的振动能量显著增加,表现为轨枕振动加速度增大,而道床吸收的振动能量降低,对道床减振有利;铺设道砟垫后,轨枕上较多的振动能量传递至道床,有利于轨枕减振。InvestigationontheDynamicBehaviorofHigh-SpeedRailwayBallastTrackStructure(AbstractofthePh.D.Dissertation)ZHUJianyue,LIANSongliang(DoctorSupervisor)(KeyLaboratoryofRoadandTrafficEngineeringoftheMinistryofEducation,TongjiUniversity,Shanghai200092,China)Accordingtothepracticalsituationsofthenewly-builthigh-speeddedicatedpassengerlinesandtheexisting200km·h-1speed-increaserailwaylinesinChina,thestructureofballasttrackisstudiedintermsoftrackdynamicresponseanalysis,establishingtherailwaytrackFEMmodel,theinfluenceoftrackirregularity,thenumericalcomputationofwheelloaddrop,theperformanceanalysisofvariousisolationpads,theinvestigationonCWRvibrationcharacteristicthroughtheharmonicresponsewayandtheindoorfull-scalemodelexperiment.Withtheregularityofrailwaytrackalongitslongitude,aspatialFEMmodelisestablishedonthenumericalcomputationmethodoftrackelementwhichis0.6mlongasequalasonesleeperspacingandincludesthedynamiccharacteristicsofonesleeperaswellascorrespondingrailmass,fastening,pad,ballastandsubgrade.Inaddition,through“cuttingandmerging”timelyoneormoretrackelementsinthefrontandrearendofthevehicle,thedynamicresponseofaboundlesstrackcanbeinvestigated.ThecomparisonbetweenthetheoreticalcalculationandthetestresultsshowsthattheFEMmodelcanbeusedtoreflectthevibrationcharacteristicsoftrackstructure.Dependingonthetheoryofvehicle-trackcouplingdynamicsandthenumericalcomputationmethodoftrackelement,theinfluenceondynamicresponseofthewheel-railsystemexcitedbyrailsurfaceverticalshort-wavelengthroughnessinCWRweldjointwithheightdifferenceissystematicallydiscussedunderdifferentrunningvelocityaswellastrackirregularityamplitude,and,thevariationofdynamicbehaviorisdescribed.Thevariousshort-termwavelengthtrackirregularitiessuchasraggedweldjoint,gagelineshellycracksandrailsurfacescratchingwhichshouldbecancelledpromptlywouldintensifythewheel-rail′sinteractionobviouslyandacceleratetheballastcrushingwhichleadtotheballastaswellasthesubgradedifferentialsettlementandthetrackdeterioration.Moreover,itisfoundthatthetrackirregularityisthemajorreasonforproducingthewheel-raildynamicforcethroughtheanalysisonthevehicledynamiccharacteristicundervariousmedium-termandlong-termwavelengthtrackirregularityexcitationontheexisting200km·h-1speed-raisinglineswhichproposesthesuggestiononcontrollingtheirregularityamplitudeandformulatingthecriterionfortrackmaintenanceanditsirregularitymanagement.Toperfectthespatialrailwaytrackdynamicanalysis,theFEMmodelanalyzingtheharmonicresponseofCWRunderanaxiallyloadisdevelopedbasedonthemodesuperpositionwayaccordingtotheenergymethodandTimoshenkobeamtheory.TherelationshipbetweenthetemperatureforceandtheresonantfrequencyaswellasthecorrespondingamplitudevalueoftheCWRvibrationcharacteristicissimulatedandcalculatedthroughthemodelunderdifferentlongitudinaltemperatureforcesandrailwayparameters.Theresultsshowthattheresonantfrequencyincreaseswhileitscorrespondingamplitudedecreasesnonlinearlywiththetemperatureforce′sgrowingandthedifferentrailandsleeperspacingwouldaffecttheresonantfrequencytocertainextent.Basedonthevirtualdisplacementprincipalforsolvingthecontact-impactproblems,theequationsofvariationcalculatingthewheel-rail′scontactunderwheelloaddropisestablishedasitsdeterminedboundaryconditionsbeingreleasedaccordingtothepenaltyfunctionmethod.DependingonthecontactcontrolaswellasthetrackdynamicequationofFEMdeducedfromthepoint-to-surfacecontactelement,thedynamicresponseissimulatedandcalculatedforthehigh-speedrailwayballasttrackstructureimpactedbythefallingwheel-set.Theresultsshowthatthetrack′sdynamicresponse,inwhichtherail′saccelerationandrailchaircounterforcevarygreatly,increasesasthedropheightraises.Thevibrationofsleeperandballastisreducedasthepadsunderrailbecomemoreelastic.Therail′sdisplacementandsleeper′saccelerationincreasewhiletherailandballast′saccelerationandrailchaircounterforcedecreasewhentheelasticpadsappliedunderthesleepers.Additionally,thepressureonsubgradesurfacedecreasesabout20%andthefoundation′svibratingisolationisenhancedeffectivelyamongadefinitivefrequencyrangeaftertheballastpadsarepaved.Itisnotedthatthespecialdesignsshouldbemadeforisolationtracksonthebasisofthetrafficconditionsandrequirementstoalleviatethewheel-rail′sinteractionbyanalyzingthedynamiccharacteristicthroughapplyingdifferentvibrationisolationsundertherail,thesleeportheballast.Bythetrackvibrationexciterandfallingwheel-set,thedynamiccharacteristicsoftheindoorfull-scaletrackmodelareanalyzedintheworkconditionssuchaschangingthesleeperkind,thetiespacing,thefasteningtype,thepadsundertherailandthesleeper,theballastpads,theballastcompactnessandsoon.Theexciterfrequencyandwheelloaddropheightarechangedtosimulatethevehicle′sdifferentrunningspeed.Toevaluatetherailwaytrackdynamicperformance,thedynamicresponsessuchasthewheel-railforce,therailorsleeper′sdisplacement(andacceleration),therailchaircounterforceetc.aretestedandmeasured.Itisshowedthatthelargerthestiffnessundertherail,thestrongertherail′svibrationenergy