Study On The Influence Of Bridge Warp Caused By Temperature Gradient On The Geometry Of Ballastless Track

The bridge has a large proportion in China?s high-speed railway line engineering,and is mainly composed of concrete box girder.The concrete box girder tends to have a temperature gradient inside the structure due to its own material properties and external environmental factors.According to the relevant codes about CWR of China,the temperature load applied on bridge is uniform,which mainly consider the influence of the additional expansion and contraction force on the strength of rail caused by the beam-track interaction,and ignore the influence of the warpage deformation on the upper ballastless track layer caused by the uneven temperature gradient of the bridge.Taking the structure of CRTSIII slab ballastless track on the bridge as an example,the finite element analysis model of ballastless track on the bridge is established.The deformation of ballastless track under different bridge temperature loads is calculated,and the influence law of the bridge warping on the geometry of ballastless track is analyzed from the angle of deformation,and the suggestions are given for the design of the CWR on bridge and the temperature load of bridge.The main research results are as follows:(1)Under the action of temperature load,the concrete box girder will produce certain warping deformation and torsional deformation along the longitudinal and transverse direction of the girder,and the deformation of the girder will be transferred to the ballastless track structure through the connection between the bridge-track system,which will have a certain impact on the vertical and transverse geometry of the ballastless track.(2)The vertical temperature gradient load of concrete box girder mainly affects the longitudinal levels of ballastless track on the bridge.It also has some influence on the horizontal geometry,but relatively small.(3)The lateral displacement of the rail is related to the transverse deformation of the girder,and also depends on the large temperature compressive stress in the rail.The vertical temperature gradient of concrete box girder has a great influence on the fluctuation of the gauge,so it is necessary to pay attention to the variation of the gauge in the vicinity of the beam end,while the increase of the gauge under the transverse temperature gradient is relatively obvious,but it is all within the limit range.(4)As for the reasonable value of beam temperature,On the basis of the complex and changeable climatic characteristics in different region of China,it is suggested to divide the land into five zones based on the existing temperature gradient code and adopt different temperature gradient bases for each partition;According to the differences between solar radiation intensity,duration of sunshine and daily temperature difference in different provinces,the different degrees of reduction are carried out on the basis of the regional temperature gradient base.It is further recommended to add the temperature gradient to the bottom plate of the box girder in the specification to more accurately simulate the vertical temperature gradient of the box girder.