Investigation on Improved Optimal Fixed Time Step in Time-History Analysis for Aseismic Design of High-Speed Railway Bridge-Track System

Time-history analysis is currently the main approach to the aseismic design of high-speed railway, and the time step significantly affects the calculation efficiency and accuracy. A 5-span high-speed railway bridge-track system was used as an example in this study. The effect of different fixed time steps on maximum seismic response was analyzed. An approach of improved optimal fixed time step was proposed by introducing maximum frequency and sampling frequency multiple. According to the research findings, for a specified ground motion record, the calculation error and efficiency of the improved fixed time step decrease with the increasing sampling frequency multiple. For a specified sampling frequency multiple, the calculation efficiency decreases with the increasing high-frequency components in ground motion record. The calculation error of secondary sampling signal for random ground motion records approximately obeys the normal distribution, and a stable and deterministic upper bound can be constructed based on the random sample of calculation error. The sampling frequency of secondary sampling signal in aseismic analysis for high-speed railway bridge-track system should be set as 4f(max). The improved optimal fixed time step should be set as (4f(max))(-1) to simultaneously satisfy both the calculation error and efficiency requirements.