Research On The Mechanical Characteristics Of Continuous Welded Rail And The Value Of Longitudinal Stiffness Of Bridge Pier On Sea-crossing Bridge In High-speed Railway

With the rapid development of high-speed railway construction,high-pier,long-span and long-bridges are widely used in engineering construction.Longitudinal stiffness of piers is related to two important issues,which are the safety of the bridge structure and the engineering cost.The force and deformation of ballastless CWR track on bridge under complex operating conditions and the dynamic effects under high-speed railway operating conditions are directly related to the safety and durability of the structure in service.Therefore,it is of great practical significance to study the mechanical characteristics of ballastless track CWR on sea-crossing bridge in high-speed railway and the value of longitudinal stiffness of piers.Based on the research background of CWR on sea-crossing bridge in high-speed railway,line-slab-beam-pier spatial coupling static model and vehicle-rail-beam-pier spatial coupling dynamic model are established in this paper.Under complex operating conditions,the static characteristics of ballastless track CWR on sea-crossing bridge in high-speed railway are studied;based on the test of the rail-fastener-ballastless track relative displacement,the new beam-rail relative displacement limit was obtained,and the design scheme of the track system on super long span and long unit continuous girder bridge;the dynamic response of the ballastless track CWR on sea-crossing bridge in high-speed railway under different parameters was studied.The main research work and conclusions are as follows:(1)In this paper,two kinds of static models of line slab beam pier space coupling of bridge type(simply supported beam and continuous beam)are established,the static characteristics of the ballastless track CWR on sea-crossing bridge in high-speed railway under the complex operation load(temperature effect,train load,load coupling,etc.)were studied.The results show that under the complex temperature load,with the increase of the cooling range,the stress and deformation of the simple supported beam and the continuous beam bridge increase significantly.When calculating the braking force,simply supported beam bridges can simplify the number of spans,6-8 spans are recommended;for continuous beam bridges,when the length of the bridge is less than 400 m,the braking force of the connecting rail is calculated according to the full span load braking of the bridge length.(2)The static characteristics of ballastless track CWR on bridge under the action of different bridge parameters(longitudinal stiffness of pier,bridge span,stiffness difference of adjacent pier line,etc.)are studied.The results show that the rail expansion force and deflection force are less affected by the longitudinal stiffness of the pier,but more affected by the bridge span;the braking force and the relative displacement of beam-rail are obviously affected by the longitudinal stiffness of the pier and the span of the bridge.For simply supported beam bridges,the linear stiffness difference of piers has little influence on the expansion force and deflection force,but has great influence on the braking force and the relative displacement of beam rail,especially the peak value.For continuous girder bridges,the difference of linear stiffness of fixed pier under the action of temperature and deflection has a great influence on the longitudinal force on the top of the pier.Under the braking load,the linear stiffness difference of fixed pier increases,the braking force and the relative displacement of the beam-rail are significantly reduced.Except for the increase of the longitudinal force on the top of the fixed pier,the other piers decreased.Therefore,it is necessary to pay attention to whether the longitudinal force on the top of the fixed pier is too large when the linear stiffness of the continuous beam pier is not uniform.(3)According to the limit value of relative displacement of beam-rail proposed by the test of the rail-fastener-ballastless track relative displacement,the reasonable value of longitudinal stiffness of simply supported beam and continuous beam piers under different spans are studied.The results show that in the relative displacement test,when the relative displacement of beam and rail reaches 5mm,no deformation or damage occurs to all structural components,it is suggested that 5mm should be taken as the limit value of relative displacement of beam-rail for the ballastless track CWR in this paper.Under the limit value,the stiffness design values of 32 m,48m,64 M,80m single box(double box)and 96 m simply supported beams are 200 k N / cm,300 k N / cm,500 k N / cm,700 k N / cm(800 k N / cm)and 2000 k N / cm(800 k N / cm)respectively;the stiffness design values of(60 + 100 + 60)m and(80 + 128 + 80)m continuous beams are 600 k N / cm and 3000 k N / cm respectively.For the study of the reasonable value of the stiffness of the continuous beam pier,it is necessary to consider the side span length of the simple supported beam.The cost of single pier can be reduced by 11.42%-36.57% after rigidity optimization.(4)Taking the continuous beam bridge of Hangzhou Bay Sea-crossng Bridge of Tongsu-Jiayong Railway as example,the track system of this type of continuous beam bridge is designed.The results show that for long-span continuous beam bridge,in order to reduce the stress on the CWR and the pier,REJs are set at both ends of the main beam respectively.The switch rail is located on the continuous main beam and does not cross the beam joint.The basic rail is located on the side span and crosses the beam joint of the main beam.Constant resistance fasteners are laid throughout the bridge.(5)The vehicle-rail-beam-pier spatial coupling dynamic model is established to explore the influence of longitudinal(transverse)stiffness of pier,angle of beam end and longitudinal stiffness difference of pier on the dynamic response of vehicle,track and bridge structure.The results show that for bridges with reasonable longitudinal stiffness of piers,the dynamic response of vehicle,track and foundation can meet the requirements of the code.The parameters such as the longitudinal(transverse)linear stiffness of the pier,angle of the beam end and the difference of the longitudinal linear stiffness of the pier are changed.The results show that the impact on the dynamic response is small,and the safety and comfort of driving are within the safety limit,which can meet the requirements of safe driving.