Three Dimensional Numerical Evaluation of a Ballasted Railway Track in Seismic Excitation

The railway networks constitute vital routes in all of the world's countries. Occurrence of earthquake events in railway locations causes the track geometry to deviate from the standard position. Remarkably, this issue is in conflict with the safe running of the train on ballasted tracks. Consequently, the seismic evaluation of railway tracks is necessary. In this study, a three dimensional numerical model has been developed for seismic analysis of the track. In this finite element numerical modeling technique, the rails and sleepers have been modeled as beam elements and the ballast and sub-ballast layers have been modeled using a spring-dash pot with lumped mass systems. In addition, the lateral and the longitudinal track resistances have been considered in the modeling process. In the next stage, due to the model sensitivity to the track length, a critical length was derived to be representative of the critical length of the track from structural and operational points of view. For this purpose, the maximum forces and deformations of sleepers and rails were considered for critical length evaluation. In the final stage, the effects of earthquakes on tracks with various stiffness values have been assessed using the evaluated critical length. The results of the seismic analysis of the model by the Kobe earthquake show that a minimum length of 40m could be selected as a critical length for seismic analysis of the track. In addition, increasing the track stiffness causes a reduction in deformations, but it has no remarkable effect on the internal forces on the track components.