Research On Force Characteristics And Structural Optimization For Longitudinal Coupled Ballastless Track Turnout On Large Bridges

With the successful construction and operation of Beijing-Tianjin intercity railway line, Longitudinal Continuously Prefabricated Ballastless Track (LCPBT) system will be more and more applied on high-speed railway and Passenger Dedicated Lines (PDLs). Due to the high requirements of railway line plane and profile, bridges and tunnels will have a great proportion on PDLs which results in the inevitable application of LCPBT system in the seamless turnout area on bridges. Based on the comprehensive research of relative fields at home and abroad, a calculation model and method for LCPBT in turnout area on bridge was built by means of the theoretical analysis and experimental study in this thesis. The systematical analysis on forces and distortion of seamless turnout, ballast-less track, bridges and other force-transferring structures were carried out.The research work and main conclusion are divided as follows:(1) Analysis of interaction between seamless turnout and bridges for LCPBT in turnout area on bridge.The LCPBT used in turnout area on bridges showed a significant advantage from the structural contrast with the two other representative ballastless turnout systems on bridges which are respectively Rheda ballastless turnout system and the urban railway track system. Then its structural characteristics, mechanical function of every part were mainly studied. Furthermore, the interaction among seamless turnout, ballasteless track, bridge beam and their force transferring mode werel researched in detail in the thesis.(2) Establishing the computing model and method of LCPBT in turnout area on bridge.Based on the longitudinal interaction relation and force characteristics of seamless turnout-ballastless track-bridge, an integral finite element model of turnout (crossover)-track slab-bridge-pier for LeiDa Bridge turnout on Wuhan-Guangzhou PDL was established. A computing program was developed using the non-linear finite element method, which can solve the complex structure. A compare between site tests and theoretical calculating results was made for the new Beibei-Jialingjiang Bridge on Suining-Chongqing test line, which primarily shows correctness of calculating theory in this thesis. Therefore, the calculating model and method for LCPBT in turnout area on bridges was considered to be reasonable that uses the similar theory with LCPBT on Beibei-Jialingjiang Bridge.(3) Analysis the longitudinal force and deformation rule of LCPBT in turnout area on bridge under temperature's influence. Taking a ballastless,350km/h, No.18 seamless turnout with movable frog on LeiDa bridge on Wuhan-Guangzhou PDL for research target, forces and distortions of turnouts, slab track, and bridges were calculated with change of some important parameters, such as extensional stiffness of track slab, friction coefficient of the slip membrane, the fixing of anchor point and rail temperature differences. The calculation items include additional forces and displacement for stock rail and slab, forces of turnout force-transfering parts, displacement of switch tongue and noise rail as well as forces of piers, anchor point, fixation point. Consequently, the longitudinal stress and deformation regularities of LCPBT in turnout area on bridges were concluded under temperature's influence.(4) Analysis the longitudinal force and deformation rule of LCPBT in turnout area on bridge under braking force and occasional force.The ballastless,350km/h, No.18 seamless turnout on LeiDa bridge on Wuhan-Guangzhou PDL was still taken for research target in order to analyse the force-transmission mechamism among turnouts, ballastless track and bridges under braking force or rail/slab breaking force. The influencing factors were analysed, such as position of train braking or rail/slab breaking, extensional stiffness of track slab, friction coefficient of the slip membrane, the fixing of anchor point. In addition, the security of structures was researched to some extent.(5) Estimating the design concept of LCPBT design in turnout area on LeiDa bridge, and performing mechanical calculation, structural design as well as optimization of some components.According to the structural characteristics of LCPBT system, some design values were researchful confirmed, including reasonable mutual location between turnout and bridge, arrangement form of bridge bearing as well as length of rub plate. Some structural design advices were put forward which might be helpful in industrial design. Force check-calculations were carried out for prefabricated slab, subbase place, slip membrane, foam plate and fixation point. Based on the author's study chance in Germany, the indoor test results of friction coefficient and durability of the slip membrane as well as durability of foam plate were researched, and some structural optimization measures were put forward, for instance, installation mode of beam crevice, anchor point and material of slip membrane.