Analysis of earthquake response of bridges in Qinghai Maduo M7.4 earthquake

Abstract

On May 22, 2021, a M7.4 earthquake occurred in Maduo County, Qinghai Province, which caused the damage of The No.1 and No.2 Yematan bridges in Maduo County. The main performance was that the longitudinal displacement of the bridge was too large, leading to the fall of the main beams of multiple spans and the damage of the bridge piers to varying degrees. According to the expert's appraisal, the intensity of earthquake influence exceeds the seismic design value of the bridge, and it is preliminarily concluded that the mechanism of the uniform beam falling damage is caused by the strong velocity pulse of the directional effect of near-fault ground motion. The investigation result of seismic impact intensity of the position of The Yematan bridge was IX .But the absence of strong vibration observation stations near the bridge and the lack of seismic records, were limited the study of the seismic response and damage mechanism of the Yematan bridge under the earthquake action. In addition, it is difficult to grasp the design parameters and damage of the bridge, and to estimate the bridge model accurately. Therefore, this paper intends to use another bridge with the same seismic fortification intensity through finite element program, using the response spectrum method as a reference, and fitting ground motion and pulse records to conduct the response time history analysis of the bridge structure, to indirectly reveal the seismic response characteristics and failure mechanism of the Bridge with Maduo earthquake. The calculated results show that the seismic response displacement and internal force of the bridge structure exceed the design value of rare earthquake, and the maximum response of one ground motion record is close to the design value of an extremely rare earthquake, which leads to the occurrence of earthquake damage or even damage of the bridge structure.

Keywords

• bridges
• ground motion
• maduo earthquake
• seismic pulse