Study On Fatigue Performance And Residual Life Of In-service Railway Steel Truss Bridge Under Heavy Haul Transportation

In recent years,with the advancement of China 's existing railways for heavy-duty capacity expansion and transportation,the traction quality of operating trains,the axle weight of trains and the traffic density have gradually increased,resulting in increasing stress amplitudes and loadings of in-service steel truss bridge structures and components.The number of cycles continues to increase,which in turn affects the remaining service life of the steel truss bridge in service and increases the risk of fatigue damage.This article takes a heavy haul railway 64 m single track under-supported simply-supported bolt-welded steel truss bridge in service as the research object,and uses a combination of finite element simulation analysis and field tests to evaluate the fatigue performance,residual fatigue life,the corresponding reinforcement technology has been studied,and the main research results are as follows:(1)Using the finite element software MIDAS/FEA,a full-space plate-shell element method was used to establish a 64 m single-line under-supported simply supported bolt-welded steel truss bridge spatial finite element model,and its dynamic response under different types of operating train loads was studied.Based on the numerical simulation results,the fatigue control members and corresponding fatigue details of the lower chord E2E4,the inclined rod A1E2,the vertical rod A1E1,the beam between the node E0 and E1 and the beam at the node E1 position were selected with the stress amplitude as the target parameter.(2)The field test results of the in-service simply supported steel truss bridge were carried out to obtain the measured results of the dynamic stress of the fatigue details of each member of the simply supported steel truss bridge under the action of the bridge natural vibration frequency and the operating train.The accuracy and reliability of the numerical simulation were verified by analyzing the measured results and comparing them with the numerical simulation results.(3)Fatigue performance of in-service simply supported steel truss bridges under the action of operating trains was carried out through the stress history of fatigue details of each fatigue control member when the operating train passed the bridge on the spot,combined with traffic statistics of various types of operating train evaluation and analysis of the current cumulative damage degree,and then use numerical simulation to obtain the stress history of the fatigue details of the fatigue control members when the large axle load train(the axle load is 27 t and above)passes the bridge,combining the current cumulative damage degree of each fatigue detail and the future operation of the large axle load train.According to the development trend of the vehicle,the fatigue performance evaluation and remaining life evaluation of the simply supported steel truss bridge in service under the action of large axle loads were carried out.(4)Combined with the current research frontiers of steel truss girder bridge reinforcement technology in current railways,the longitudinal beam reinforcement technology of steel truss girder bridges in service under heavy axles is discussed.The remaining life before and after the longitudinal beam reinforcement of the steel truss bridge is compared and analyzed.The results show that the fatigue life of the fatigue details of the stringer fatigue control members increases significantly after reinforcement with 20 mm thick steel plates,which verifies the applicability of the reinforcement technology.