Analysis On Reasonable Values Of Transition Track Structures At The Beam-end Of Ballastless Track On High-Speed Railway Bridges

There will be rotation angles or dislocation displacement at the ends of high-speed railway bridges under the action of train loads,creep deformation of concrete,uneven settlement of bridge pier foundation,as well as temperature differences.When the displacement at the beam ends is greater than the requirement of the safety limit specified in the code,it will exert a negative influence on the safety of the train running and the ride comfort of the passengers.It is universally acknowledged that setting transition plate at the ends of the beam is an effective measure to ameliorate the force of the rail structure near the beam ends.Nevertheless,few work has been done about what kind of parameters of the transition plates can make the force of the tracks decrease furthest and what influence will be exerted on the running stability of the train after the setting of the transition plates.In this work,the reasonable range of the parameters of the transition plates the fastener system are studied through the static and dynamic analysis.The main contents and achievements are as follows.(1).The mechanism of transition plates is studied in detail.What's more,by analyzing the stress characteristics and transmission way of track before or after setting up transition plate,it is found that the force of track caused by deformation of beam-end after setting up transition plate can really be decreased.(2).The finite element models of static analysis of two-span 32m simply-supported beam with and without transition plate are established by ANSYS.The length of the transition plate is 2.5m.From the research we can draw the following conclusions:After setting the transition plate,it seems that the force of track can be most decreased under the action of the angle displacement of the single side beam-end.Meanwhile,the maximum downlift forces of the fastener can be reduced by 75%-83%under the action of 0.5mm-3mm dislocation of the single side of the beam-end.Similarly,the maximum uplift force of the fastener can be reduced by 79%?85%under the selected working condition of the rotation angle occurs on one side of the beam-end while the dislocation occurs on the other side and the minimum stability coefficient of the track slab can be increased by 275%?301%under the selected working condition of the symmetry angle of the beam-ends occurs.(3).The calculation models of vehicle,track,bridge and transition plate are derived respectively based on the relationship between wheel and rail,and the motion equations of the train-ballastless track-transition plate-bridge system are derived.Meanwhile,the Newmark-beta method is applied to solve the equations.According to the motion equation of the system,a program for solving the vibration response oftrain-track-transition plate-bridge system is compiled by MATLAB.The program is used to calculate the running smoothness of the train when passing through the transition plate before or after adding the transition plate at the beam-end.Finally,it is found that the maximum vertical vibration acceleration of the car body increases greatly while the comfort index of Sperling has little change after the setting of the transition plate.(4).According to the results of static and dynamic analysis,the reasonable values of transition track structure at the Beam-end of Ballastless track for high-speed railway bridge are obtained.Namely,the stiffness of the fastener over the transition plate should be controlled from 19kN/mm to 40kN/mm.The spacing of the fasteners over the transition plate should be controlled from 600mm to 630mm.The length of the transition plate should be limited from 1.3m to 2.5m.The stiffness of the transition plate need to be not less than 0.2×3.2×10-3m4 by changing the moment of inertia of the transition plate and the distance value between the track-end fastener to the bearing of the transition plate should be controlled from 325mm to 400mm.