Vertical Modeling Of Heavy Haul Railway Vehicle/Track/Bridgre System And Dynamic Performance Optimization

With the developing needs of transport speed,axle load and long grouping of the heavy haul railway,higher requirements on the safety and durability of vehicle-track-bridge(VTB)system are put forward.An effective way to provide design basis for railway design to meet the requirements is to establish dynamic simulation model of vehicle-track-bridge system to study the dynamic response and make optimizations.In this study,the vehicle was considered as a multi-rigid body system,the ballast track-bridge finite element equations of heavy haul railway were derived,the vertical dynamic model of vehicle-track-bridge system was established based on Hertz nonlinear wheel rail relationship,the dynamic responses of vehicle-track-bridge system were solved by iterative solution method with Matlab programs and compared with the measured data to verify the model.And then the parameters of vehicle,track and bridge were selected,the change regulations of the peak responses of the system under different track structure parameters were studied.Finally,based on the laws of change,the cases of single target with single class dynamic peak response or multi-classes dynamic peak responses optimization were calculated combined with the genetic algorithm optimization method based on Pareto ranking,and the optimum structure parameters under different cases were obtained.Through the research,the following conclusions were drawn:(1)The change of track structure parameters in the system has effects on the peak value of each component of the system with different extents.The changes of rail pad stiffness kp or track bed thickness hb had great effects on vertical acceleration and speed peak responses of rail,sleeper and ballast,especially the acceleration peak responses,had little effect on the response of bridge,and the vertical displacement responses of the whole system were not affected.(2)As for the results of single objective optimization(SOP)cases,when the peak value of rail acceleration response was minimal,the rail pad stiffness kp was 160 MN/m,the track bed thickness hb was 0.31m.When the peak value of ballast acceleration response was minimal,the rail pad stiffness kp was 60 MN/m,the track bed thickness hb was 0.6m.When different optimization results were compared with each other,the values of rail pad stiffness kp or track bed thickness hb exist difference,However,the responses in the system level should be taken into account in the actual project.(3)As for the results of multi-objective optimization(MOP)cases,when the combination was rail acceleration and sleeper acceleration response or the combination was rail acceleration and ballast acceleration response,the optimal rail pad stiffness kp was 180 MN/m,the optimal track bed thickness hb was 0.39m.When the combination was sleeper acceleration and ballast acceleration response,the optimal rail pad stiffness kp was 160 MN/m,the optimal track bed thickness hb was 0.60m.The optimized values given reasonable values for reference of rail pad stiffness and track bed thickness based on the structural dynamic response.This study gave the reference value of rail pad stiffness and track bed thickness based on the vehicle-track-bridge system dynamic responses.(4)As for the results of optimization efficiency,the number of optimization for each case is 3,and the results of all 3 optimization were consistent,that showed the genetic algorithm optimization method was of high efficiency.