Structural Mechanical Characteristics And Parameter Optimization Of Transition Plate At Beam End Of Lakge Ramp Bridge On Ballastless Track

With the optimization of the road network layout,the construction of high-speed railways is rapidly advancing to the central and western regions.The central and western regions are facing a complex natural environment,and the ballastless seamless tracks on long ramps and bridges will be widely used.There is no ballast track on the bridge on the ramp.The expansion and contraction deformation caused by the temperature difference of the beam body will have a significant impact on the force of the fasteners near the beam seam.If superimposed with other external loads,the force of the beam end fasteners may exceed the limit,set at the beam end The transition plate can improve the stress and deformation characteristics of the beam-end track structure,and the value of the transition plate structure parameter is of great significance to ensure the reasonable stress of the beam-end track structure and the safety of train operation.In this paper,a spatial coupling model of the ballastless track seamless track on a large ramp bridge is established,and the mechanical characteristics of the additional transition plate structure at the bridge end on the slope are studied from both static and dynamic aspects,and the value of the transition plate structure parameters are optimized,and Determine the slope limits of different bridge temperature spans according to the optimized results.The main research content includes the following 5aspects:(1)Aiming at the problem of excessive vertical deformation at the end of the continuous beam bridge on the ramp,based on the finite element method,the beam-slab-rail interaction mechanism and the vehicle-track coupling dynamics theory,the rails,fasteners,and ballastless tracks are fully considered The spatial dimensions and mechanical properties of structures such as,bridge girder body,transition plate,etc.,and the spatial coupling static model of the beam end transition plate structure of the ballastless track on the large ramp bridge and the spatial coupling dynamics of high-speed railway vehicles-track-transition plate-bridge are established model.By comparing with the existing research results,the correctness of the model in this paper is verified.(2)Based on the spatial coupling static model of the transition plate structure of the beam end of the ballastless track on the large ramp bridge,the force characteristics of the beam end track structure with and without the transition plate are compared,and the temperature difference of the beam body and the bridge are analyzed.The influence of temperature span,slope and other factors on the force of the track structure at the beam end.The results show that for the bridge on the ramp,the maximum tensile force and maximum pressure of the beam end fasteners increase linearly with the slope of the bridge and the temperature of the beam body,and increase with the increase of the temperature span of the bridge;the additional transition plate structure at the beam end of the bridge does not increase.The maximum tensile force of fasteners is reduced by 70.6%～76.8% in the transition plate structure;when designing the seamless track on the bridge,when the environment of the bridge is determined,from the perspective of improving the force on the track structure at the beam end,it is recommended to reduce it as much as possible Longitudinal slope,when the slope is large,a simple beam bridge or a small span continuous beam bridge is used.(3)Based on the built high-speed railway vehicle-track-bridge-transition plate spatial coupling dynamic model,the influence of the transition plate structure on the dynamic characteristics of the beam-end track structure is studied.The results show that: compared with the bridge beam end without a transition plate structure,the vertical displacement of the rail at the beam joint increased by 2.6%,the acceleration decreased by 39.1%,and the vertical displacement of the track plate increased by 50.3 after the addition of the transition plate structure at the beam end.%,the acceleration increased by 466.4%,the vertical acceleration of the car body increased by 1.9%;with the increase of the slope,regardless of whether the transition plate structure is added to the beam end,the vertical acceleration and displacement of the rail at the beam joint,the transition plate(track Plate)vertical acceleration and displacement,and the vertical acceleration of the car body gradually increase,but the increase is not obvious.(4)Comprehensive dynamic and static analysis results,from the perspective of improving the stress on the track structure at the beam end,the value of the transition plate structural parameters is optimized.It is recommended that the length of the transition plate is2.5m,and the fastener spacing of the transition plate is selected.630 mm,the rigidity of the fastener on the transition board is 30 k N/mm,and the distance between the fastener on the end of the transition board and the support is 315 mm.(5)With the increase of the temperature span of the continuous beam bridge,after the optimized transition plate structure is added to the beam end,the slope limit corresponding to the continuous beam bridge gradually decreases;The maximum pull-up force of the beam end fastener determines the slope limit of the bridge,When the temperature spans of continuous beam bridges are 88 m,101m,124 m,160m,188 m,and 210 m,the slope limits of the bridge are recommended to be 35.0‰,33.4‰,27.8‰,21.5‰,20.5‰,19.4‰,respectively.