System-level seismic fragility of high-speed railway track-bridge system with component-replaceable U-shaped combined steel damper

A component-replaceable U-shaped combined steel damper (UCSD) was presented as an energy dissipation device to mitigate the seismic damage of high-speed railway track-bridge system (HSRTBS). The energy-dissipation modules inside the UCSD can be replaced by removing the high-tensile bolts. A low cyclic test of the energy dissipation module was carried out. Parametric analysis of the UCSD with varying U-shaped plate thicknesses was conducted using finite element analysis, including 8, 10, 12, 14, and 16 mm. To study the effect of the UCSD on HSRTBS under near-fault ground motions, twenty-eight near-fault records recommended by FEMA-P695 were selected, and the UCSD was installed adjacent to bearings in HSRTBS. Component-level fragility curves of HSRTBS with UCSDs with the different thicknesses of U-shaped plates were compared. To comprehensively and efficiently evaluate the contribution of the UCSDs on HSRTBS, system-level fragility curves were obtained by the product of the conditional marginal (PCM) method. Results indicate that the UCSD exhibits excellent hysteresis performance and energy dissipation capacity, improving with the U-shaped plate. At the maximum considered earthquakes (MCE) level, the exceeding probability of complete damage of the system is reduced from 100 % to 95 %, 79 %, 57 %, 35 %, and 20 % respectively after adding UCSDs in five different U-shaped plate thicknesses. This reveals that the proposed UCSD can effectively mitigate HSRTBS seismic damage under near-fault motions, progressively improving with increased U-shaped plate thickness.