Dynamic performance evaluation of a railway bridge post-end-support region under different rail pad conditions and operating train speeds

The present study examines the constitutive-level behavior of geomaterial layers beneath railway tracks at the bridge post end-support zone. Its originality lies in independently evaluating the effects of rail pad stiffness variations and train speeds on the structural response of track and adjacent bridge substructure. This critical end-approach region exhibits boundary conditions distinct from the open track, necessitating rigorous performance evaluation. A rigorous finite element analysis was performed for a real-field case, incorporating the nonlinear characteristics of geomaterials and simulating moving loads within a dynamic framework. Results indicate that significant rail displacement persists up to 6 m from the post end-support, beyond which the influence of train speed reduces. Under low-speed conditions with rigid rail pads, vibrations transmit deeper into the ballast layer. Conversely, at higher speeds, soft rail pad promote a significant retention of high-frequency vibrational modes within deeper zones, particularly near shorter transition distances.