Evaluation Of Fatigue Performance Of Railway Prestressed Concrete T-Girder Bridge

With the rapid development of China’s transportation,especially the development of railway transportation,railway prestressed concrete T beam bridge has become a major form of railway bridge network composition,which plays an important role in the development of railway transportation in China.At the same time,the traction quality,axle load and driving density of the operating trains have also gradually improved,which makes the fatigue damage of many prestressed concrete bridges accumulate significantly under the long-term action of repeated train loads.Therefore,in order to ensure the safe use of existing railway prestressed concrete bridges,it is necessary to study the residual fatigue life and related safety assessment systems.In this paper,a railway prestressed concrete T girder bridge is used as the research object,and the fatigue performance and residual fatigue life of the bridge under the action of the train are studied,and the main research results are as follows:(1)By studying the stress characteristics of the prestressed concrete T girder bridge,the most susceptible to fatigue failure of the bridge during operation is obtained,that is,the middle and upper part of the bridge span.The whole process of axle coupling was simulated by Ansys simulation,and the stress time history at the fatigue position was calculated by software.(2)The influence of these changes on the bridge was explored under the conditions of different axle loads,different proportions of prestress damage and different number of cars per train formation.The fatigue performance of these conditions was evaluated separately,and the residual life of the bridge was further predicted.It is found that the axle load of the train,the initial prestress damage of the bridge and the increase in the number of cars in a single train formation make the damage accumulation rate of the bridge faster and faster,and its life gradually decreases,for example,the life of 16 cars without prestress damage is 262,162 and85 years with the increase of axle load.(3)The impact of the load and environmental factors of the bridge during operation is complex and changeable,which will lead to the degradation of the performance of the bridge structure during operation is also uncertain.In this paper,the gamma stochastic process was used to simulate the fatigue damage process of the bridge,and it can be observed that the cumulative damage process of fatigue rises in multiple steps.Compared with the continuous linear change of the empirical formula,from a local point of view,the different degrees of changes in each stage of the gamma process are more realistic.On the whole,the total number of injuries between the two in a certain time frame is relatively close.(4)For different axial loads or considering different proportions of prestress damage,gamma random process simulation is used,and the life estimated by gamma random process method is very close to the life estimated by constitutive model method,and all meet the law that the service life of the bridge gradually decreases with the increase of axle load of trains or the increase of the proportion of prestress damage.Therefore,the gamma process can be used to simulate the development of damage during the actual operation of the bridge,so as to grasp the damage of the bridge.