| The Sichuan-Tibet Railway is a major strategic project for building a comprehensive transportation system and a strong transportation nation in the new era.It is also an "Economic Artery" that promotes regional development and promotes the construction of the "One Belt and One Road".The Sichuan-Tibet Railway crosses the first and second steps,across the Hengduan Mountains to the Qinghai-Tibet Plateau,with a large topography and a strong plate activity zone.Due to the complex geographical and geological environment of the railway line,natural disasters such as collapse and rockfall are extremely prone to occur.Once it occurs,it will pose a serious threat to the safety of trains running on the bridge.Therefore,in order to ensure the safety of railway operations,it is of great significance to study the safety of trains running on bridges under the impact of rockfalls.This paper takes the 32.6m simply supported box girder bridge of the Sichuan-Tibet Railway as the research object,and explores the timehistory response of the bridge under the impact of rockfalls and the running safety of bridge.The main research contents and conclusions are as follows:(1)Based on the collision and impact theory and calculation method,the integrated modeling method of Rhinoceros,Hypermesh and LS-DYNA is used to establish a refined simulation analysis model of a simply supported box girder bridge under the impact of rockfall that fully considers nonlinear factors,and the impact load of the train-track-bridge system is obtained.Based on train-track-bridge coupled vibration analysis theory and multi-body dynamics theory,using ANSYS and SIMPACK co-simulation platform,fully considering the wheel-rail contact nonlinear relationship,the train-track-bridge coupled vibration analysis model under the impact of rockfall is established through the elastic body method and the flexible track method.(2)Based on the established simulation model of the simply supported box girder bridge under the impact of rockfall,the dynamic response and damage mechanism of the bridge pier under different rockfall impact conditions are discussed.The research results show that the impact of rockfall will cause the bridge structure to produce a large impact force and lateral dynamic response in a short time;the impact force and lateral dynamic response will increase as the impact velocity and diameter of the falling rock increase,the impact position is close to the top of the pier,and the impact angle decreases;the increase in the impact angle of the rockfall essentially reduces the horizontal impact velocity;when the impact force reaches45.1MN,the maximum lateral displacement of the box girder is 7.8mm,which exceeds the specification limit(3)Based on the established train-track-bridge coupled vibration analysis model under the impact of rockfall,the time-history analysis of the train-track-bridge system under the impact of rockfall is carried out to explore the influence of impact on the running safety of bridge.The research results show that the train on the bridge has a slight suppression effect on the lateral forced vibration of the bridge under the impact of rockfall;the lateral wheel-rail force,derailment coefficient and wheel load reduction rate of the train increase rapidly within a short time of the impact of rockfall,and then decay periodically;because of the high self-weight of the train,the moment when the wheel load reduction rate reaches its maximum value due to the reduction of the vertical wheel-rail force is slightly delayed than the lateral wheel-rail force and the derailment coefficient;when the impact force is 23.0MN and the impact position is 2m below the top of the pier,the maximum wheel load reduction rate of the 200km/h train increases to 0.71,which exceeds the specification limit;when the impact force is 45.1MN and the impact position is 10 m below the top of the pier,the maximum wheel load reduction rate of the train at a speed of 200km/h is 1,and the speed limit should be limited to pass the bridge. |
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