Deterioration of dynamic response during high-speed train travelling in tunnel-bridge-tunnel scenario under crosswinds

The infrastructure types such as bridge-tunnel connection have become increasingly common along the highspeed railway lines in rugged terrains. The deterioration of traffic safety is inevitable when evoking the sudden variation of aerodynamic load when a train is running at the junction of two infrastructure scenarios (bridge to tunnel or tunnel to bridge) in a windy environment. This study is dedicated to discussing the temporal characteristic of aerodynamic loads acting on a three-car train by simulating an actual running process-running on an tunnel-bridge-tunnel infrastructure in canyon wind environment (TBT-W)-in the CFD software. The dynamic responses of the train when running in the TBT-W scenario, including the displacement and acceleration parameters, the wheel-rail response and the traffic safety indices, are analysed by constructing a wind-train-bridge dynamic coupled system. Results show that the deterioration effect of traffic safety does exist because of the sudden variation in aerodynamic impact at the junction of two infrastructure scenarios with respect to the single infrastructure scenario of bridge under crosswind; the time-resolved effects caused by the rapid transformation of train running scenario remarkably increase the fluctuation amplitudes of the aerodynamic forces and moments; the sudden variation effect of aerodynamic loads when a high-speed train runs in the transition section of tunnel-bridge is more remarkable than that at the bridge-tunnel junction; the wheels in the leeward side, especially for the leading vehicle, present the highest safety risk when running at the tunnel-bridge junction due to the high values of the traffic safety indices.