Research On Rail-Rail Interaction And Smoothness Of Long-Span Cable-Stayed Bridges

Bridges are an important part of the foundation of the high-speed railway line.When the high-speed railway line crosses roads,rivers,mountain streams or areas with poor geological conditions,it provides a stable and smooth foundation for the high-speed railway.It is more than 40,000 kilometers long in my country There are nearly 20,000 kilometers of railway bridges in the operating mileage of high-speed rail.With the increasing passenger volume of high-speed railways in recent years,the demand for crossing railway bridges and the timeliness of high-speed railways are also increasing,and more and more long-span railway bridges have begun to lay ballastless tracks.At the same time,in order to meet the running requirements of high-speed trains,the long-span railway bridges with ballastless tracks also put forward higher requirements in terms of geometric smoothness,structural stiffness and dynamic response.In this paper,an integrated model of rail-beam-cable-tower-pier is established based on the engineering background of the Changqing Yellow River Bridge of Zhengji High-speed Railway.Based on the finite element method,the effects of train load,temperature,earthquake,cross wind and other factors on the mechanical properties of the seamless track on the longspan cable-stayed bridge and the geometric smoothness of the ballastless track are analyzed.The main work content and research results are as follows:(1)The expansion and contraction force of the seamless line is mainly affected by the temperature change of the main beam.The uneven temperature difference caused by sunlight,the temperature change of the main tower,the stay cable and the track structure have little effect on the longitudinal additional force of the steel and the relative displacement of the beam and rail.Under the braking load,a rapid relative displacement of the beam and rail of about0.55 mm will occur within the action range of the braking load on the main beam,and the rest of the main bridge except the action range of the load is the beam-rail fixing area.The beamrail rapid relative displacement amplitude is only affected by the loading position of the braking load,and has nothing to do with the loading length.(2)In order to improve the force of the boss and the elastic backing plate in the beam end area,the CRTS III ballastless track slab lower three boss scheme is proposed and studied.Under the action of temperature,the boss force and the compression amount of the elastic pad in the beam end area are larger,and the amplitude of the boss force and the compression amount of the elastic pad are 140 k N and 0.5mm,respectively.After using the ballastless track slab lower three boss scheme,the boss force is reduced from 140 k N to 94 k N,the compression amount of the elastic pad is reduced from 0.5mm to 0.36 mm,and the boss force and the compression amount of the elastic pad are reduced by 30%.(3)From the aspect of influence degree,the biggest influence on the rail smoothness is the train load,followed by the sunshine temperature difference(along the beam height direction),and finally the tower beam daily temperature difference and the beam cable temperature difference.In the operation stage of long-span railway cable-stayed bridges,the upper arch of the beam caused by the heating of the main girder,the heating of the main tower and the cooling of the stay cables can slow down the deflection of the beam caused by the train load to a certain extent,and reduce the amplitude of the track unevenness.,to improve smoothness.The temperature difference of the stay cable and the sunshine temperature(along the beam height)will increase the amplitude of the track irregularity.(4)Under the action of earthquake,the setting of the telescopic adjuster will have a great influence on the longitudinal force amplitude of the rail.When the telescopic adjuster is set,the longitudinal force amplitude of the rail is 385.39 k N.When the telescopic adjuster is not set,the longitudinal force amplitude on the rail is 3919.05 k N,far exceeding the allowable tensile force of the rail.Under the action of the earthquake,affected by the longitudinal stiffness of the main beam,the longitudinal displacement time-history curves of the beam bottom at different positions are basically the same,and the longitudinal displacement amplitude is about 20 mm.The lateral displacement amplitude of the beam bottom above No.2 pier is the largest,followed by No.1 pier,and No.3 pier is the smallest.The lateral displacement amplitudes are 24.27 mm,28.17 mm,and 8.18 mm,respectively.