青海玛多M7.4地震中桥梁地震破坏现象分析

2021年5月22日青海省玛多县发生了M7.4地震,造成玛多县境内的野马滩1、2号桥破坏,其主要表现为桥梁纵向位移过大导致多跨主梁落梁,桥墩也有不同程度的破损.经现场专家鉴定,地震影响烈度均突破桥梁抗震设计值,并且初步判断这种整齐划一的落梁震害的机理系近断层地震动方向性效应的强速度脉冲作用所致.野马滩大桥位置的地震影响烈度调查结果为Ⅸ,但是野马滩大桥附近无强震动观测台站,大桥附近没有获得地震动记录,这不利于野马滩大桥地震作用下地震响应和破坏机理的研究.另外,野马滩大桥的设计参数和折损情况也很难掌握,桥梁模型难以准确估计.为此,本文拟采用另一座同等抗震设防烈度的桥梁,通过有限元程序,使用反应谱法作为参考,同时使用拟合的地震动和脉冲记录进行桥梁结构反应时程分析,以便间接地揭示玛多地震桥梁地震反应特征和破坏机理.计算结果分析表明,所分析的桥梁结构地震响应位移和内力均超过罕遇地震设计值,其中一条地震动记录最大反应接近极罕遇设计值,导致桥梁结构出现破坏甚至损毁震害现象的出现.

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

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 con-duct the response time history analysis of the bridge structure,to indirectly reveal the seismic response characteristi-cs and failure mechanism of the Bridge with Maduo earthquake.The calculated results show that the seismic re-sponse 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.