Analytical Study on the Safety of High Speed Railway Vehicle by Track Excitations on Earthquakes : Based on the Simulation Model with Wheel-Set Yaw Motion( D & D 2008)

Recent reports imply that railway vehicles could be derailed solely by the ground motions of earthquakes without fatal damages of vehicles or tracks. Based on the reports and facts, we believe that we should further study the derailment mechanism of a high speed railway vehicle excited by large seismic motions, to pursue to minimize the risk of railway system safety against large earthquakes. We improved our original planar vehicle dynamics simulation model to a model to allow yaw motion of wheel-set, which enable to estimate the influence of the attack angle of wheel/rail and steering effort of the wheel contacting to rail at flange and yielding large radial difference. Through the analyses based on the new model, the following outcomes were obtained. (1) Most of derailments are brought as the result of the rocking motion of a vehicle by track excitations underneath. The excitation amplitudes for derailment are influenced by vehicle speed particularly in lower input frequencies. (2) Wheel climb derailment is not observed. We attribute it to the negative attack angle of wheel/rail during wheel/rail flange contact. (3) At the moment just before derailment when wheel is contacting on rail at flange top, the steering effort of wheel-set, which may contribute to avoid or delay derailment, is not observed.