Dynamic Characteristics Analysis Of Ballastless Track On Bridge Under Braking Load

With the rapid development of high-speed railway,the unballasted track CWR on bridge get more and more applications.The safety of the high-speed train on the bridge and the stability of the track and bridge structure become a hot research issue.There is not enough theoretical research on the force and deformation characteristics of CWR on ballastless track under train load and braking load.Therefore,the dynamic response of ballastless track on the bridge under the action of braking load is studied,which will be of great guiding significance for the design and can provide theoretical basis and technical support for the safety of high-speed train running on bridge and the stability of track and bridge structure.This paper starts from the dynamic analysis model of high-speed train-ballastless-bridge longitudinal and vertical coupling system,studies the dynamic response of vehicle subsystem and ballastless track-bridge subsystem in vertical and vertical direction,and conducts further study in this field to provide a strong reference value.According to the characteristics of high-speed train-ballastless-bridge dynamic interaction,the vehicle unit and ballastless track-bridge unit which is suitable for this problem are proposed.Using finite element method and Lagrange equation,the dynamic analysis model of longitudinal coupling system of high speed train-ballastless track-bridge is established respectively.The whole model includes the vehicle subsystem model and the ballastless track-bridge subsystem model,the two are coupled by the wheel-rail relationship.The size of the braking force is determined by the train braking deceleration characteristic curve.The Hertz theory is used to solve the wheel-rail forces and the cross-iterative algorithm is used to solve.The numerical differential equations of the two systems are solved by using MATLAB program.A case study of emergency braking on ballastless track of four-section-type CRH2 EMU,the results show that the longitudinal and vertical displacements and accelerations of the track and bridge structures are decreasing,and the vertical vibration of the track structure at the beam end is larger than that at the midway.The train speed is gradually reduced during the braking process.The longitudinal displacement of the track structure and the bridge is abruptly reversed,the longitudinal acceleration is abruptly changed,and then there is a tendency of free decay.When the train stops,the train and the bridge will appear the vertical maximum vibration.The research results can provide theoretical support for the design of ballastless track on bridge.For the example,the influence of driving speed,wheel-rail friction coefficient,elastic coefficient of cushion plate and elasticity coefficient of CA mortar on the vertical and longitudinal dynamic response of two subsystems were analyzed by the program and got the following conclusions:(1)The influence of train speed on the vertical and longitudinal dynamic responses of the two systems is significant,especially for the acceleration of the ballastless track-bridge subsystem,the value of the system is multiplied,but when the brake stops,the vertical vibration of the two systems has no influence,but the effect on the longitudinal vibration is gradually increased.Therefore,the reasonable control of the vehicle speed is helpful to improve the traffic safety and the stability of the track and bridge structure;(2)The influence of wheel-rail friction coefficient on longitudinal dynamic response of vehicle subsystem and ballastless track-bridge sub-system is obvious.As the wheel-rail friction coefficient increases,the longitudinal acceleration of the vehicle body,bogie,wheel and longitudinal wheel-rail force are gradually increased,and longitudinal displacement and longitudinal acceleration of the bridge structure are gradually increased.While the train stopped,the longitudinal dynamic response of vehicle subsystem and ballastless track-bridge subsystem increases with the increase of wheel-rail friction coefficient;(3)The vertical and longitudinal dynamic responses of the sub-system of the vehicle and the ballastless track-bridge system are calculated for different cushion elastic coefficients and the elastic modulus of the CA mortar,and the range of the longitudinal and vertical parameters of the ballastless track structure on the bridge is discussed.;(4)The high-speed train-ballastless track-bridge longitudinal-vertical coupling system dynamic model and cross-iterative algorithm of proposed in this paper provide theoretical basis for further study on the dynamic performance,to design parameters and related standards of ballastless track on bridge,And the theory is generally applicable to the analysis of bridges and other ballastless track structure on the roadbed.In the end,it summarizes the main work of the paper,points out the shortcomings of this subject and the problems that need to be extended.