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Influence of velocity pulse effect on earthquake‑induced track irregularities of high‑speed railway track-bridge system under near‑fault ground motions

Shaohui Liu, Lizhong Jiang, Wangbao Zhou, Jian Yu, Yulin Feng, Zhenbin Ren

Archives of Civil and Mechanical Engineering

2024

Vol. 24, no. 2

art. no. e70, 2024

The near-fault ground motion records show a noticeable velocity pulse effect, which poses a significant seismic threat to the high-speed railway track-bridge system. This study conducts the seismic response analysis of the track-bridge system under near-fault ground motions with forward directivity and fling-step effects. It quantifies the degree of damage of each track-bridge system’s key component using the component's stiffness degradation coefficient. In addition, this research investigates the influence of velocity pulse effects from near-fault ground motions on earthquake-induced residual geometric irregularities and earthquake-induced dynamic irregularities. It explores the post-earthquake running performance of high-speed trains based on the input of earthquake-induced irregularities, providing a theoretical basis for the seismic design method of the track-bridge system based on running safety. The research results indicated that the stiffness degradation of the track-bridge system under near-fault pulse-type ground motions is more severe compared to near-fault non-pulse ground motions and mid-far-field ground motions. The amplitudes of earthquake-induced residual geometric irregularity and earthquake-induced dynamic irregularity of rails under near-fault pulse-type ground motions are much greater than those under near-fault non-pulse and mid-far-field ground motions. The earthquake-induced alignment irregularity significantly impacts high-speed trains' derailment coefficient and transverse acceleration. Consequently, failing to account for the velocity pulse effect of near-fault ground motions can lead to an over-estimation of the post-earthquake running capacity of the track-bridge system. Seismic design considerations for high-speed railway bridges must prioritize the influence of velocity pulse-type ground motions.