Interlayer area damage modeling and damage-based seismic fragility analysis of high-speed railway bridge and track system

A novel interlayer damage model is proposed to assess the seismic performance of the track subsystem in a high-speed railway bridge-track system (HSRBTS). The track subsystem can be treated as a long multilayer structure with vertically compact and longitudinally continuous interlayer bonding, leading to a particular damage mode, namely, interlayer separation in a certain area. This differs from the bridge subsystem and moment resisting frame dominating by the failure of sidesway collapse, generally measured by the maximum peak interstory drift. For this specialized structure, a novel framework of the interlayer area damage model (IADM) with a matrix -based damage indicator DIA is developed in a beam-spring finite element model of HSRBTS. Multi-resolution damage measures are derived for the seismic performance evaluation for different engineering demands. This scheme is adopted in a 5-span-simply-supported HSRBTS to carry out the seismic fragility analysis via incre-mental dynamic analysis. The result indicates that DIA quantitatively describes the distribution and size of interlayer area damage regions along the entire track subsystem, which is important for the evaluation on structural demand and train running safety of HSRBTS. Compared to the traditional damage model, the IADM provides more informative damage states in seismic fragility analysis. At a lower to moderate intensity measure level, sliding layer performs more vulnerable, but it is prevented from longitudinally through interlayer damage as observed in CA mortar layer. A critical damage state is revealed by IADM, facilitating the determination of the onset of interlayer overall failure of the track subsystem.