Analysis On The Collapse Mechanism Of Xiaoshan Workers’ Road Ramp Bridge

Hangzhou Xiaoshan District Workers pedestrian ramp bridge collapsed in April 2017,the bridge for the pedestrian ramp curve bridge.During the service period,only non-motor vehicles passed.Therefore,the reason for the collapse and the traditional curved girder bridge due to overloading of vehicles caused by the overturning is different.Taking Xiaoshan workers’ road ramp bridge as the research object,this paper analyzes the causes of the collapse accident through the following three aspects:Firstly,the original design and construction data of the bridge were collected systematically.At the site of the collapse,the strength of the debris was detected and the contact was established according to the collision marks.The four states before the collapse were summed up by the reduction of the collapse process according to the contact collision.Secondly,the finite element model of the four states before the collapse is established by using the ABAQU finite element software,and the cause of the collapse is analyzed.The results of the finite element calculation are compared with the traces in the field.Thirdly,the MIDAS finite element software is used to establish the two linear model of the East and west side of the Xiaoshan workers road ramp bridge.The possible causes of the critical state of the collapse are analyzed.At the same time,the influence of the seismic action on the curved beam bridge is compared and analyzed.The results show that: Because the section of box girder is changed from symmetry to asymmetry,and the construction of bearing cushion is error,the lateral bearing force is too large.When occurring in a nearby M4.2 earthquake,the corresponding box girder’s anti slip structure is invalidated,so that the superstructure continues to slip outward and move close to the 20 cm.Finally,the bearing cushion rock is damaged locally,which leads to the continuous collapse of the bridge.