Damage mechanism and failure chain of CRTS III slab ballastless track high-speed railway bridges under earthquake excitation

China's high-speed railway (HSR) has entered the operation and maintenance stage. Exploring the damage mechanism of HSR is of great significance in determining its post-earthquake functional usability. China Railway Track System III (CRTS III) Slab Ballastless Track (SBT) is a mainstream track system independently developed by China, but the damage mechanism and failure chain of the HSR CRTS III SBT simple-supported bridge (SSB) is still unclear. To explore the damage mechanism and failure chain of the HSR SSB under the action of different combinations of seismic directions, a test of CRTS III SBT was carried out to explore the constitutive relationship of the isolation layer. Then based on the test data, a non-linear finite element model (FEM) of CRTS III SBT SSB for HSR was built and validated. The vulnerable parts of the HSR SSB system under earthquake excitation were analyzed, and the damage distribution pattern, damage and failure sequences of vulnerable parts under four kinds of earthquake conditions were investigated. According to the research, the most vulnerable components of the HSR SSB system were the bearings, piers, and fasteners under earthquake, The fixed bearing experienced earlier failure than the sliding bearing, The pier's damage under transverse seismic was far smaller than that under longitudinal seismic, The failure chain of the HSR SSB system were different under transverse and longitudinal earthquake, During the bridge design phase, it is suggested to strengthen the middle span bearing and pier, and to strengthen the fasteners at the beam joints without affecting the track smoothness.