Coupled dynamics of high-speed trains and turnouts under traction/braking conditions with rail profile optimisation

To investigate the impact of traction/braking behaviour on the dynamic response of turnouts, this study uses the CRH380A train and the No.18 high-speed turnout as case studies. A rigid–flexible coupled dynamic model of a high-speed multiple unit and turnout was developed, incorporating the effects of traction/braking forces. The dynamic behaviour of multiple unit passing through turnouts and the factors influencing these responses were analysed. Based on measured turnout rail profile data, a method for optimising rail profiles considering traction and braking effects was proposed. Results show that the peak wheel–rail lateral force and carbody lateral acceleration of the leading car in an 8-car formation are 1.19 and 1.52 times greater, respectively, than those of a single-car model, indicating that train formation amplifies lateral dynamic responses. Traction/braking torques primarily affect carbody vibrations and wheel–rail wear. Initial speed significantly influences wheel–rail impact forces, while the friction coefficient strongly affects lateral dynamic behaviour. The optimised rail profile achieves a more uniform contact stress distribution, reduces dynamic impact, and significantly enhances train safety when passing through turnouts.