Research On Dynamic Characteristics Of Ballastless Turnouts On Viaducts In High Speed Railway

High speed railway in China is featured by ballastless track oriented and numerous viaducts. With large scale construction of high speed railway in our country, turnouts as important railway equipments are laid on viaducts inevitably, and the viaduct-ballastless turnout structure system has come into being. When trains pass at high speed, vehicles, ballastless turnouts and viaducts interact with one another, and constitute a high speed railway vehicle-turnout-viaduct coupling system (VTV system). It colligates technological characteristics of ballastless tracks, high speed turnouts and viaducts, and leads to a series of technological difficulties related to the high speed, which has become an urgent problem required to solve.Based on investigation and analysis on dynamics literature including vehicle-track system, vehicle-turnout system, vehicle-bridge system and vehicle-track-bridge system, using multi-body dynamics theory and finite element method, dynamic simulation and calculation platform FORSYS is developed independently. Combining with field tests carried out in Zhengzhou-Xi'an passengers dedicated line and Beijing-Shanghai high speed railway line, theoretical and experimental research on dynamic characteristics of ballastless turnouts on viaducts is carried out. It can provide theoretical support for the development, application and dynamic evaluation of ballastless turnouts and viaducts in high speed railway. The main research contents are as follows:(1) A new dynamic simulation and calculation platform FORSYS is developed.There are some shortcomings for modelling vehicles, tracks and substructures using commercial calculation softwares and self-programming softwares. For example, multi-body dynamics simulation softwares can not be used for detailed simulation of tracks and substructures, and finite element analysis softwares are difficult for multi-body dynamics modelling of vehicles. Self-programming softwares can realize hybrid modelling of multi-body model and finite element model, but it is hard to simulate structure details, and often heavy workload. So aiming at the shortcomings of these research methods, dynamic simulation and calculation platform FORSYS is developedFORSYS is composed of FORTRAN self-programming module and ANSYS software module. ANSYS module is mainly used for modelling turnout and bridge structures, and FORTRAN module is mainly used for modelling vehicle structures, dealing with geometry relationship of wheel/rail contact, calculating the dynamic interaction between vehicle and turnout, and solving the system dynamic equation, etc. Using FORSYS platform, vehicles, turnouts and bridges can be modelled quickly and accurately, and vehicle model (multi-body model), turnout model and bridge model (finite element models) can be rigid-flexible coupled easily. It can make up for the shortcomings of commercial and self-programming softwares. It is a new dynamic analysis method.(2) A complete and detailed vehicle-turnout-track-viaduct coupling system dynamic analysis model for high speed railway is established.According to mechanical characteristics of high speed railway vehicles, ballastless turnouts and viaducts, dynamic simulation and calculation platform FORSYS is used for establishing vehicle-turnout-track-viaduct coupling system dynamic analysis model. The system model is composed of vehicle model, turnout model, bridge model, vehicle/turnout interaction model and turnout/bridge interaction model.In the system model, vehicle is discreted as rigid body system composed of carbody, bogies and wheelsets. Vibrations of switch panel, closure panel and crossing panel are all considered in turnout model, the variations of rail sections are considered, nonlinear forces of jacking block, spacer block and sliding platform are also considered, and ballastless tracks are simulated used solid elements. Bridge model is established according to the drawings, and variations of bridge sections and bridge bearings are considered.(3) Experimental research on ballastless turnout on viaducts in high speed railway is carried out, and vehicle-turnout-track-viaduct coupling system dynamic analysis model is validated.Dynamic field tests of ballastless turnout on viaducts are carried out in Weinan North station of Zhengzhou-Xi'an passengers dedicated line and Xuzhou East station of Beijing-Shanghai high speed railway line. Dynamic responses such as vertical and lateral wheel/rail forces, rail displacements, rail accelerations, rail dynamic stresses, slab accelerations, bridge accelerations and deflections are measured when vehicles pass through turnouts.According to test results, the system dynamic characteristics are evaluated from the aspects of vehicle/turnout dynamic interaction, vehicle running safety and comfort, turnout dynamic characteristics and bridge dynamic characteristics. By comparing simulation results to test results, vehicle-turnout-track-viaduct coupling system dynamic analysis model is validated.(4) Dynamic characteristics of vehicle-turnout-viaduct system are simulated and analyzed.Using the validated dynamic analysis model, dynamic characteristics of vehicles, turnouts and bridges are researched when vehicles pass through turnouts in main line and branch line, from the aspects of vehicle/turnout dynamic interaction, vehicle running safety and comfort, turnout dynamic characteristics and bridge dynamic characteristics.(5) Influencing laws of dynamic parameters of vehicle-turnout-viaduct coupling system in high speed railway is researched.Using the system dynamic analysis model, influencing laws of dynamic parameters associated with vehicle, turnout and bridge structures are researched. It can provide theoretical support for optimization design, application and development of turnout and bridge structures in high speed railway.