Analysis Of Longitudinal Force Characteristics Of CRTSⅡ Slab Ballastless Track On Multi-span Simply Supported Beam Bridge

CRTSⅡ slab ballastless track is a longitudinal slab ballastless track.The mechanical equilibrium system of mutual restriction and coupling between bridges and track structures of different layers is constituted by non-linear constraints.Accurately grasping the stress of each structural layer and components is especially important for the design,construction,operation and maintenance of CRTSII type slab ballastless track structure.In this paper,for the 32m standard span simply supported beam bridge commonly used in high-speed railway,the longitudinal force characteristics of the simply supported beam bridge and the CRTSⅡ type slab ballastless track structure are analyzed in detail.The main research work and conclusions are as follows:(1)Based on the bridge-orbit interaction mechanism,the theoretical calculation formula of the longitudinal force of CRTSII type slab ballastless track on the bridge is derived.Through the finite element software ANSYS,an integrated fine model of the pier-beam-base plate-rail plate-rail and subgrade is established.(2)The stress and displacement characteristics of the CRTSⅡ type slab ballastless track on the bridge under the conditions of train braking condition,beam telescopic condition,track plate and track bed plate breaking condition are analyzed.The distribution characteristics and transmission law of longitudinal force in the beam body and each layer of track structure.The results show that:1)Under the braking condition,the longitudinal force of the track structure gradually changes from tension to pressure,and the longitudinal displacement increases first and then decreases.When designing the calculation,the most unfavorable loading position should be selected according to different parts.At the same time,in addition to checking the shear groove,double-line loading should be used.2)Under the telescopic condition,the longitudinal force of the track structure decreases from bottom to top,and the maximum value of the base plate pull and pressure reaches about 100kN.The abutment is stressed,which should be paid attention to in the design check.3)Under the condition of broken plate,the longitudinal force released after the break of the track plate is mostly carried by the base plate,and the base plate may be pulled off.The longitudinal resistance of the fastener within 4.6m of the broken joint is over-limit,27.6m range Shear failure occurs in the CA mortar layer;when the track bed is broken,the longitudinal resistance of the fastener in the range of 69.1m at the fracture is over-limit,and the double-line has shear failure of the CA mortar layer,and the shear groove near the fracture It is very likely to be cut,so in order to avoid the large additional force caused by the breakage of the track plate and the track plate,the construction quality of the ballastless track must be guaranteed.(3)Discussing the telescopic stiffness of the track bed,the longitudinal stiffness of the CA mortar layer,the friction coefficient of the sliding layer,the longitudinal stiffness of the bridge abutment,the length of the friction plate,the span of the simply supported beam and the structural structure to the longitudinal forces of the structural layers and the connecting members.Influence the law.The results show that:1)The telescopic stiffness of the track bed plate has obvious influence on the longitudinal force of the bridge beam body and the track structure of each layer.Therefore,the structural rigidity should be considered in the structural calculation.2)The friction coefficient of the sliding layer has a significant influence on the longitudinal force of the bridge track system under braking and telescopic conditions;under the condition of the broken plate,the shearing force on the shear groove at the joint is greatly affected.3)The longitudinal stiffness of CA mortar layer has a great influence on the shear displacement of CA mortar layer,and has limited influence on other aspects of the system.4)The bigger the stiffness of pier and abutment,the smaller the braking force of track structure of each layer,and the bigger the braking reaction force of pier and abutment;the bigger the stiffness of pier and abutment is,the bigger the expansion reaction force of pier and abutment is,and the limited influence on other components;the bigger the stiffness of pier and abutment,the smaller the additional force of each layer of track of non-broken plate side.5)According to the distribution of reaction force when the length of friction plate is different,the suitable length of friction plate is 75m under the condition of braking and expansion.6)With the increase of bridge span,the braking force of bridge increases obviously;the expansion force of track structure increases in varying degrees;when the slab is broken,the additional shear extreme value of the side shear slot of non-broken slab and the longitudinal additional reaction extreme value of pier and abutment increase with the increase of span.7)The braking force of simple-supported beam,continuous beam and rigid-frame continuous beam are close,and the expansion force and interstory displacement of simple-supported beam bridge are smaller than those of the other two.