Seismic vulnerability assessment of a railway beam bridge considering brittle failure of the restrainer in a friction pendulum system

Abstract

The restrainers in the friction pendulum system (FPS) may experience brittle failure during an earthquake. Strong nonlinear behavior should be considered to precisely assess the seismic performance of the railway beam bridge under an earthquake. A seismic vulnerability assessment was performed based on a typical simply supported railway beam bridge. Three different models of the FPS in fixed direction were considered: elastic restrainer model, brittle restrainer model, and nonrestrainer model. Through dynamic analysis, the responses of the railway beam bridge were obtained, including the force and displacement of the FPSs, the curvature ductility at the pier bottom, and transverse dislocation at the beam gap. The analysis results pointed out when the earthquake intensity exceeded the fundamental intensity, the brittle failure of the restrainers was very likely to happen. The sudden release of energy introduced a displacement pulse to the FPS. The elastic restrainer model overestimated the force demand and damage probability of the substructures but underestimated the FPS displacement and dislocation at the beam gap. The nonrestrainer model seriously underestimated the force demand of the substructure and the FPS displacement under strong earthquakes. The brittle restrainer model could reflect the nonuniform failure of the restrainers and provide a more accurate estimate of the transverse dislocation at the beam gap.