Simplified Analysis Model of Longitudinal Constraint Effect of High-speed Railway Simply-supported Bridge Under Earthquake

Abstract The structure of a high-speed railway (HSR) bridge with a track system is complex, and the computational efficiency of seismic analysis for a fine HSR bridge with a track system model (BM) is low. This study considers an HSR bridge with CRTS II slab ballastless track system as a case study and develops a simplified model (SM) based on a method for simulating track constraints with equivalent springs. To obtain the optimal stiffness of SM equivalent springs, a finite element (FE) structural parameters updating framework utilizing an improved genetic algorithm (GA) is established, and the updated SM's dynamic characteristics and seismic response are compared to BM's. In addition, it uses SM to analyze the over-limit state and applicability of the bridge structure's critical components. The results indicated that the model simplification ratio of SM reaches 95%. The seismic response outcomes of SM and BM accurately agree with an average relative error of 3% and a maximum relative error of less than 5%. The over-limit state of the seismic response structure tends to be stable as the number of ground motion samples increases. The shear and bending capacity of the pier and the deformation of the fixed support have a high over-limit risk under longitudinal seismic, which is worth noting in the engineering design.