Seismic isolation of railway bridges isolated with a novel multi-stage friction bearing

Abstract

Conventional bridges are highly vulnerable to strong and mega-earthquakes. To improve seismic performance and achieve controllable structural behavior under high-intensity ground motions, this study introduces a novel Multi-stage Friction Bearing (MSFB) featuring a multi-stage activation mechanism. The bearing provides three-stage functionality—“rigid connection → friction damping → potential energy-based displacement restriction”—through its composite horizontal and inclined sliding surfaces. The research methodology encompasses three key phases: First, the restoring force model of the MSFB across its distinct operational stages is derived through theoretical analysis. Subsequently, comprehensive mechanical performance tests validate the accuracy of this model. Finally, the effectiveness of the MSFB in controlling the seismic response is evaluated through numerical simulations of a realistic three-span simply supported girder bridge. The findings demonstrate that the MSFB successfully implements its three-stage mechanism, transitioning smoothly between stages based on seismic excitation intensity. Under moderate earthquakes, the MSFB functions as an effective isolator, elongating structural periods and dissipating seismic energy. During major earthquakes, it acts as an effective displacement-restriction device, mitigating seismic damage risks of by preventing girder unseating and superstructure collisions.