Seismic response of concrete bridge of Lanzhou-Xinjiang high-speed railway under the near-fault strong earthquake

Abstract

The MS6.9 earthquake in Menyuan, Qinghai, on January 8, 2022 caused severe damage to Sulphur Gully Bridge of Lanzhou-Xinjiang high-speed railway. In this paper, a two-dimensional numerical model of the structure and site soil is established with Sulphur Gully Bridge as the research object, and finite element dynamic time analysis is used to study the dynamic response characteristics of the box girder, pier, pile foundation and site of Sulphur Gully Bridge under ground motion loads. The results show that the peak acceleration in the pile and bridge superstructure system as a whole decreases linearly with height, the horizontal peak displacement of the bridge pile-superstructure system decreases linearly with height, and the peak displacement of the soil site as a whole gradually decays linearly as it is amplified farther from the bridge, and the horizontal peak displacement in the direction of the source is smaller than that of the site further away; the difference between the vertical peak displacement and the horizontal peak displacement is the difference between the vertical peak displacement and the horizontal peak displacement is about 5–13.6 times; the vertical peak displacement of the middle of the bridge pier and the pile changes very little as the height decreases, and the vertical peak displacement of the soil layer site as a whole gradually decays as the distance from the bridge is enlarged; the ground motion frequency of the bridge is mainly concentrated in 1–10 Hz, and the main frequency is distributed in 2 Hz, the peak Fourier spectrum of ground motion in the pile-superstructure system tends to decrease as the height decreases, and the peak Fourier spectrum of ground motion is the relationship is: box girder > abutment > soil site > pile; the relationship between the peak of ground motion energy spectrum of bridge is: pile > soil site > abutment > box girder.