Lateral Seismic Performance and Lateral Restraining Block Collision Mechanism of the CRTS II Slab Ballastless Track System on Bridges

To investigate the lateral seismic performance and collision mechanism of lateral blocks in the high-speed railway CRTS II slab ballastless track system on bridges, this study established a refined three-dimensional integrated finite element model of the track–bridge system based on an [Formula: see text] simply-supported girder bridge. Using nonlinear time-history analysis, the lateral dynamic response of the track system and the collision effect of lateral blocks under seismic excitation were systematically examined. The results show that the track structural response increases nonlinearly with increasing ground motion intensity, and the beam joints are stress concentration zones and vulnerable locations. The interlayer components exhibit a progressive energy dissipation mechanism in the order of “fixed bearings [Formula: see text] movable bearings/shear grooves/sliding layers.” The critical peak ground acceleration (PGA) threshold for collision between lateral blocks and track slabs ranges from 0.34[Formula: see text]g to 0.35[Formula: see text]g. The collision effect is significantly influenced by the frequency characteristics of the ground motion; when the predominant frequency of the input ground motion matches the natural frequency of the bridge (3.78–5.68[Formula: see text]Hz), a “resonance-like effect” occurs, intensifying the collisions. The lateral blocks in the side spans are identified as the most vulnerable parts experiencing the most severe collisions. This study provides a theoretical basis for the seismic design of CRTS II slab ballastless track systems on bridges.