Influence Of Vehicle-Bridge Coupling Effect On The Safety Of Vehicles On Bridge During Earthquake

With the continuous development of high-speed railways in our country,railway lines will have to cross seismically active zones.Due to the requirements of construction,environment,train operation,etc.,bridges account for a large proportion of the railway lines in China.The safety of trains running on bridges under earthquakes is particularly important.At present,most of the analysis of the safety of trains on bridges during earthquakes is to build a detailed vehicle–track-bridge calculation model to evaluate the operational safety of trains through wheel weight reduction,derailment factor,wheel-rail lift and wheel-rail excursion.The above method is complicated in calculation,which is not convenient for engineers to use.This paper examines the influence of vehicle-bridge coupling effects on derailments to simplify safety assessment of train operation on bridges under earthquakes.Specific research content includes:(1)The effects of vehicle-bridge mass ratio,bridge frequency,vehicle speed and ground vibration on the degree of vehicle-bridge coupling were investigated by controlling variables using the vehicle–track-bridge coupling model and the decoupling model,respectively.The results show that the vehicle-bridge mass ratio is the main factor that affects the vehicle-bridge coupling degree.When the vehicle-bridge mass ratio is less than about 0.1,the vehicle-bridge response can be calculated by direct decoupling.(2)The effects of moving forces,bridge torsion,and other factors on the derailment of the train on the bridge were analyzed under the earthquake.The example of a simple-supported beam bridge with high piers used in this paper shows that the main incentives for train under the earthquake come from the lateral displacement and torsion of the bridge.Considering the piers as cantilevered beams,a single-freedom decoupling model considering torsion is proposed based on the relationship between transverse displacement of the pier top and transverse torsion.Using the four measured ground motions as the excitation,under different bridge lateral frequencies and vehicle-bridge mass ratios,the single-freedom decoupling model considering torsion and coupling model are used to calculate the critical PGA when the train derails.The results show that when the mass ratio is less than 0.1,it is approximated that the train derailment can be calculated using the single-freedom decoupling model considering torsion.(3)The single-degree-of-freedom decoupling model,the single-freedom decoupling model considering torsion and coupled model are used to calculate the SI_L limit of the bridge deck vibration intensity when the train derails.The single-freedom decoupling model considering torsion has better accuracy.Based on the the single-freedom decoupling model considering torsion,the SI_L limit of bridge deck vibration intensity is obtained.Finally,two examples are given to illustrate the applicability of bridge deck vibration intensity SI_L.