Influence Of Uneven Settlement Of Bridge Pier And Creep Camber Of Bridge Girder On The Running Safety For High-speed Railway

The development of high-speed railway in China has been changed from massive construction to safe operation period.Affected by special region and complex environment,high-speed railway bridges inevitably produces additional deformation under the settlement of pier,shrinkage and creep of concrete,temperature variation and earthquake,which can affect the track smoothness and safe operation of vehicles,and has adverse effects on operation of high-speed railway.In this study,the additional deformation of rail is obtained by the universal analytical model which describes the relationship between bridge vertical deformation and track geometry.Meanwhile,a high-speed train-bridge coupling vibration model based on the co-simulation method that integrates the muti-body dynamics and FEM,that consists of the high-speed railway train CRH2,6×32 m-span simply supported girder bridge and CRTS I ballastless track slabs are presented to study the mechanism and variation of the dynamic performance of the high-speed train-bridge coupling vibration system under the uneven settlement of pier,creep camber of bridge girder and the coupling effect of them.And the thresholds of uneven settlement of pier and creep camber of girder are investigated according to safety and comfort of train operation.The main research contents and conclusions are as follows:(1)A review is performed for the effect of the bridge deformation caused by uneven settlement of pier,creep camber of bridge girder and other factors on the operation of highspeed railway vehicles.Drawbacks in existing studies are pointed out,and the significances of studying the dynamic responses of the train-bridge coupling vibration under the the uneven settlement of pier,creep camber of bridge girder and the coupling effect of them and putting forward the thresholds of uneven settlement of pier and creep camber of bridge girder are elaborated.(2)A summary of the theory of vehicle-bridge coupling vibration including the basic assumptions and dynamic equations is introduced.Then,a high-speed train-bridge coupling vibration model consist of a dynamic model of the high-speed railway train CRH2 whice contains 31 DOF and a FE model of the 6×32 m-span simply supported girder bridge is established based on the co-simulation method that integrates the FEM software ANSYS and muti-body dynamics software SIMPACK.The wheel-rail contact relationship adopts the Hertz nonlinear elastic contact theory vertically and the Kalker linear creep theory tangentially.The track irregularity of the German high-speed low disturbance line is generated by using the trigonometric series method.The high-speed train-bridge coupling vibration model is validated by the field test of the Shizikou Bridge,located on the railway line between Yichang and Wanzhou in China.The calculated and measured values for natural vibration frequency of bridge and response of the deflection in midspan are analyzed contrastively to indicate the highspeed train-bridge coupling vibration model is effective and reliable.(3)The additional deformation of rail caused by uneven settlement of pier,creep camber of bridge girder and the coupling effect of them is obtained via the universal analytical model which describes the relationship between bridge vertical deformation and track geometry.And the variation trend and development law of the additional deformation of rail are analyzed.Then,the additional deformation is superimposed on the random irregularity of the German low disturbance line as the excitation for the high-speed train-bridge coupling vibration model.(4)Four specific conditions of uneven settlement of pier are defined,including the settlement of single pier,relative rising of single pier,settlement of two adjacent piers,and settlement of two non-adjacent piers.The dynamic response of the lateral acceleration,vertical acceleration,derailment coefficient,wheel unloading rate and lateral wheelset force of the vehicle have been studied.The results show that the uneven settlement of pier has obvious effects on the vertical dynamic responses and few effects on the lateral dynamic responses.The vertical acceleration,derailment coefficient and wheel unloading rate increase with the raise of the settlement of pier and vehicle speed.And the lateral acceleration and lateral wheelset force also increase with the raise of vehicle speed,but there is little variety with the change of the settlement of the pier.The vertical acceleration is most sensitive to the variation of the settlement of the pier and reaches the limit first.According to limit of the vertical acceleration,the threshold of uneven settlement of pier is 11.67 mm.(5)Theories of the concrete creep mechanism,influence factors and calculation models are described first.Then a finite element model of 32 m-span simply supported girder bridge is establish by FEM software MIDAS CIVIL to study the deformation with different operating time.And the sine curve is used to fit the deformation.The safety indexes of train operation including derailment coefficient,wheel unloading rate and lateral wheelset force and the comfort indexes of train operation including lateral acceleration and vertical acceleration with various creep camber of bridge girder and speed have been calculated by the high-speed trainbridge coupling vibration model.The results show that creep camber of bridge girder has obvious effects on the vertical dynamic responses and few effects on the lateral dynamic responses.The safety and comfort indexes of train operation increase with the raise of vehicle speed.The vertical acceleration,derailment coefficient and wheel unloading rate have a positive correlation with the creep camber of girder.And the lateral acceleration and wheel unloading rate have no obvious variety with the change of the creep camber of bridge girder.The vertical acceleration is most sensitive to the variation of that creep camber of bridge girder and reaches the limit first.According to the limit of the vertical acceleration,the threshold of that creep camber of bridge girder is 12.31 mm.(6)To study the influence of coupling effect of uneven settlement of pier and the creep camber of bridge girder on the dynamic response of vehicle-bridge coupled vibration system,combining the settlement of two non-adjacent piers and the creep camber of bridge girder as working condition.The results show that compared with the dynamic response under the uneven settlement of pier and the creep camber of bridge girder,the dynamic responses under the coupling effect of them are stronger.The vertical acceleration and wheel unloading rate increase with the raise of the settlement of the pier,the creep camber of girder and vehicle speed.The vertical acceleration is more sensitive than wheel unloading rate to the variation of the settlement of the pier,the creep camber of bridge girder and reaches the limit first.According to limit of the vertical acceleration,the thresholds of uneven settlement of pier and creep camber of girder respectively are 11.12 mm and 11.78 mm.