Sensitivity of seismic vulnerability curves of high-speed railway bridges to the quantity of ground motion inputs

Ground motion input uncertainties may significantly affect structural seismic responses, resulting in an overestimation or underestimation of structural vulnerability results. To address this issue, a typical high-speed railway (HSR) bridge is taken as an example in this study, and a minimum quantity of ground motion inputs to balance computational costs and calculation accuracy. Seismic responses and vulnerabilities of multiple bridge components are first obtained using incremental dynamic analysis (IDA) and probabilistic seismic demand model (PSDM). The system vulnerability is then evaluated by using first-order bounds. Finally, the sensitivity of seismic vulnerability to the quantity of ground motion inputs is explained through statistical theory. Analytical results show that increasing the quantity of ground motion inputs from 3 to 7 can effectively reduce the calculation error from +/- 38% to +/- 15%. A minimum quantity of 11 ground motion inputs is strongly recommended for seismic vulnerability analysis to ensure acceptable calculation accuracy (>= 94%).