Study On Response Behavior Of Turnout Beam Under Multi-Dimensional Earthquake

As a typical natural disaster,earthquake will cause bridge damage every time,and then affect the road network traffic.As a key link of the railway transportation network,turnout beam adopts the special-shaped structure in order to meet the needs of train line switching and cross-line transportation and is subject to the topographic conditions.It has the characteristics of skew bridge and curved bridge.The structural asymmetry,centroid-of-mass deviation and bent-torsion coupling will lead to the extremely complex seismic response behavior of the beam body.It is urgent to carry out research on beam response behavior under multi-dimensional earthquake.The main research work in this thesis is as follows:(1)By referring to the modeling methods and ideas of relevant literature,a refined rail-beam-pier coupling nonlinear model is established.The dynamic characteristics of turnout beams are explored through modal analysis.The influence of support stiffness and sliding layer on dynamic characteristics of turnout beams is analyzed by changing the bearing stiffness and setting sliding layer;(1)By referring to the modeling methods and ideas of related literature,the CRTSⅡ slag-free track structure was established to consider the track constraint effect,and the refined rail-beam-pier coupling nonlinear model was constructed;(2)The modal analysis of the switch beam model without and with track constraint is carried out respectively,and the dynamic characteristics of the switch beam body and the influence of track constraint on the dynamic characteristics of the switch beam body are obtained.By changing the support stiffness and setting sliding layer,the modal analysis of the switch beam model is carried out,and the influence law of the support stiffness and setting sliding layer on the dynamic characteristics of the switch beam is obtained.The final model is selected as the object of numerical simulation according to the analysis results of dynamic characteristics combined with the actual situation;(3)7 seismic waves(5 natural waves +2 artificial waves)were selected according to relevant specifications and the peak acceleration was uniformly modulated to 0.5g.Longitudinal seismic loading,transverse seismic loading and seismic wave loading considering incident angle are respectively carried out on the model with 7 selected seismic waves to explore the response behavior of turnout beam and beam under horizontal unidirectional seismic loading.On this basis,the track structure is considered to explore the influence of track constraint effect on the response behavior of beam under horizontal unidirectional earthquake.The research finds that:Considering the effect of track constraint,the longitudinal impact response of the beam body will be weakened on the whole,and the development trend of the transverse impact of the beam body will be changed,so that the transverse impact number and the peak value of the collision force will be small at both ends and large in the middle;(4)In order to study the response behavior characteristics of the beam under multi-dimensional earthquake,the selected seismic waves were respectively loaded into the model in two dimensions and three dimensions.By comparing the response behavior data of the beam under two-dimensional earthquake,three-dimensional earthquake and horizontal unidirectional earthquake,the influence of multidimensional earthquake on the response behavior of the beam is analyzed.Comparative analysis is conducted to study the influence of track constraint effect on the response behavior of beam under multi-dimensional earthquake by considering the relevant data before and after the track constraint effect.The study finds that:considering track constraint effect will weaken the longitudinal collision response of beam,change the trend of transverse collision frequency of beam,reduce the transverse collision frequency of most blocks,and increase the peak value of collision force in the middle part of beam.