The influence of spherical bridge bearings on train running safety during earthquakes considering train-track–bridge interaction and soil specification

Currently, while various earthquake mitigation strategies for railway bridges have reached a mature stage, the focus on ensuring train safety during seismic events remains limited. Based on considering different earthquake intensities and sites, this study introduces a three-dimensional train–track–bridge coupling model by taking China Railway Track System (CRTS) II plate ballastless track, a simply supported girder bridge and a train set as examples. It refines traditional train running safety indexes and evaluates the influence of spherical steel bearings (SSBs) on the running safety of trains amid seismic activities. The results show that in areas with hard soil layers, the number of SSB damages varies with the earthquake intensities, and whether the SSB is damaged marginally affects trains running safety during earthquakes. However, in regions with soft soil layers, the longer ground motion periods adversely affect SSBs, leading to significantly larger displacements in damaged SSBs compared to undamaged ones, thereby posing a greater risk to train running safety, especially as the earthquake intensity increases. Thus, for enhanced running safety, particularly in areas with suboptimal soil conditions, larger displacement design values (i.e., increased bearing stiffness) should be adopted, and efforts should be made to limit the sliding of SSBs post-damage.