The Design And Dynamic Analysis Of Steel-spring Floating-slab Track For No.9Turnouts On Metro Line

ABSTRACT:In recent years, more and more urban metro lines have been built, so turnouts are hard to pass the places sensitive to vibration. The requirement of steel-spring floating-slab for turnouts is more, but most of the slabs have not operated. Because of these and the complex structure of floating-slab in turnouts, it is necessary to study the design and stiffness uniformity of steel-spring floating-slab tracks for turnouts. Based on the design of the steel-spring floating-slab track for NO.9turnouts in one Beijing metro line and summarize of the studies in the domestics and overseas, this paper establishes three-dimensional finite element models of floating-slab track and vehicle-track coupling dynamic models. Then the steel-spring floating-slab tracks for turnouts are analyzed from the aspects of statics, vibration transmissibility and driving dynamic.Firstly, this paper analyzes the design of steel-spring floating-slab tracks for turnouts form static analysis. The moving static loads are applied on the main line and branch line of turnouts to solve the envelope graphs of displacement and bending moments, so as to determine the most unfavorable load position, and then the longitudinal and lateral stress and displacement of floating-slab track are investigated on the most unfavorable load position. The conclusions show that:The wider the slab, the more uniform the force along lateral from the front to end of the slab; switch groove and crossing are the weak parts of the turnout slab as a result of the thin slab in switch groove and the intensive steel-spring under crossing; increasing the stiffness of steel-springs under the slab between crossing and the end of the floating-slab can increase stiffness uniformity of the slab; although floating-slab is not uniform, but it is within the allowable scope of criterion.Secondly, the vibration characteristics of steel-spring floating-slab tracks in turnouts are analyzed to analyze the stiffness uniformity of turnouts. By applying excitation in different positions of main line, branch line, vibration acceleration of different positions and frequencies of rail and slab along the longitudinal and lateral direction are compared. The vibration acceleration of floating-slab turnouts and common turnouts is also compared. Conclusions show that:vibration acceleration of different positions is different along the longitudinal and lateral of slab but small difference; the vibration response of stock rail is greater than the vibration of closure rail; the vibration response of slab under stock rail is greater than the vibration of slab under closure rail; the vibration amplitude of slab in switch groove is larger; the vibration amplitude of slab in crossing is smaller.Finally, dynamic characteristics of vehicle systems and different positions of floating-slab tracks in turnouts are analyzed under the vehicle dynamic loading. The results show that:the dynamic response of floating slab in turnout is almost the same from the front to the end of the turnout slab; stiffness inhomogeneous are found in the switch groove and frog, the dynamic response is great; from the frog to the end of the slab, because of the large width of the slab, the dynamic characteristics of stock rail and closure rail quite different, the dynamic characteristics of slab under stock rail and closure rail quite different, the dynamic irregularities are caused by the stiffness irregularity of the slab.Combined with engineering practice, the static and dynamic characteristics of steel-spring floating-slab track structure in turnouts under vehicle load are studied; the analysis method and relevant conclusions in this paper can provide some theoretical reference for design and application of steel-spring floating-slab track in turnouts.