Damage dispersion study of high-speed railway track-bridge system with the UCSD considering train effects

High-speed railway track-bridge systems (HSRTBSs) are subject to rigorous safety performance criteria. Components within the bridge and track structures, such as bearings and CA mortal layer, are susceptible to severe damage during earthquakes, probably compromising running safety. An available way to control seismic response is installing damping devices. However, few research focuses on the contribution of dampers to response of HSRTBS considering train effects. This paper delineates the development of a finite element model of a five-span simply-supported HSRTBS, augmented with prefabricated and modularized U-shaped combined steel dampers (UCSDs), via OpenSees. A high-speed train, running on the HSRBTS, is simulated through the moving spring mass column method (MSMCM). An innovative index, damage dispersion (7), is proposed based on the seismic fragility analysis of two groups of components, categorized by their relative fragility in the HSRBTS, to probabilistically assess the impact of the dampers on seismic damage distribution among the system. The result shows that the UCSDs effectively disperse damage from more vulnerable components (fixed bearings, sliding layers, and CA mortar layers) to stronger ones (piers and fasteners). The observed decrease in the median and standard deviation of 7, identified as a logarithmic normal distribution, implies that UCSDs contribute to a more uniform damage distribution across the system, even when train effects are considered. The variation trend of 7 with PGA shifts from an increase to a modest decline, and the values of 7 exhibit a systematic reduction after considering train running, partially attributable to the train bogies in dissipating energy.