Fatigue Analysis And Reliability Study Of Heavy Railway Bridges Based On Vehicle-bridge Coupling Vibration

With the development of the country’s economy,the demand for transportation has also greatly increased.Under the background,bridges,as one of the most important parts of traffic system,have become one of the key points of construction and development.The total mileage of railway bridges across the country has exceeded140,000 kilometers,of which heavy-duty railways occupies a very important position,especially the Shuohuang railway,which has undertaken the main freight transport task.In recent years,in order to meet the increasing demand for transportation volume,the Shuohuang railway has carried out capacity expansion and transformation.Increased axle load and operating density make bridges along the line to work under high load for a long time,causing serious fatigue deterioration,which seriously threatened the safety of vehicles and bridges.Therefore,it is necessary to study the Shuohuang railway bridge.This article has mainly done the following works:(1)A vehicle-bridge coupling dynamic analysis model is established.The dynamic balance equation of the vehicle and the bridge is theoretically derived.And the calculation formula of the force between the wheel and the rail under the specific wheel-rail model is given.Using the whole process iteration method,the vehicle and bridge responses are solved in Matlab.(2)Based on the vehicle-bridge coupling dynamic analysis program,a typical32-meter simply supported beam bridge of Shuohuang Railway was studied.The research results show that axle load has a greater effect on the vertical dynamic performance of the bridge.The greater the axle load is,the greater the vertical deflection and acceleration are.Train speeds have an effect on the lateral and vertical dynamic performance of beams.When speed increases,the horizontal response and vertical response also increase nonlinearly.Generally speaking,increasing production capacity will increase the power response of Shuohuang Railway,which is not good for long-term operation.(3)Based on the vehicle-bridge coupling dynamic program,the displacement time history of 5000t-train,10000t-train and 20000t-train is obtained,and then the stress time history of ordinary tensile steel bars and shear stirrups is solved respectively.By Rainflow-Method,the stress amplitude are obtained.Based on the linear accumulation principle the fatigue damage and the fatigue life can be solved.(4)A reliability algorithm based on vehicle-bridge coupled random vibration theory is proposed.The fatigue limit state function under the heavy-load railway is established.The track irregularity is used as a random excitation.The probability analysis of each variable in the limit state function is carried out.the probability distribution of the equivalent stress amplitude and the number of cycles when the train passes the bridge is studied.The Monte Carlo method is used to solve the failure probability and fatigue reliability.(5)Studies have shown that the stirrups are more dangerous under the fatigue load of the train,and will destroy within 100 years.Therefore,The steel plate reinforcement method and steel-concrete combined reinforcement method are proposed,and the bearing capacity and fatigue performance of the reinforced beam are evaluated in last chapter.It is proved that the two methods can effectively improve the shear fatigue life of the beam end.The two methods have their own advantages and disadvantages.In practice,a suitable reinforcement scheme can be selected as appropriate.