Study on Optimal Bracketed Duration Scheme of Seismic Time History Analysis for High-Speed Railway Track-Bridge System

Seismic duration significantly impacts the structural seismic response. In order to obtain a correct time history analysis result of structural seismic design, determining a reasonable seismic duration scheme is imperative. In this paper, a five-span simply supported beam bridge and China Railway Track System (CRTS) II slab ballastless track system is taken as the research focus. A finite-element model for a high-speed railway track-bridge system was developed. The influence mechanism of starting and end threshold on seismic response was analyzed. Different bracketed duration schemes were put forward, and their applicability was assessed. The optimal bracketed duration scheme of time history analysis for a high-speed railway track-bridge system was determined. The results indicate a response curve deviation between the full duration and partial duration in the starting part due to the inconsistent structural movement trends and a deviation in the end part because of the structure entering a free vibration state in advance. When calculating the seismic peak response, the starting threshold A and end threshold B at both ends should be taken as 15% of peak acceleration. When calculating seismic residual response, the starting threshold C at the left end should be taken as 25% of peak acceleration.