Research On Structure And System Dynamics Characteristics Of Floating Slab Track Bed With Damping Pad In Metro

The problems of environmental vibration and sound wave pollution near subway tunnels caused by the operation of subway trains are becoming more and more serious;the use of floating slab track beds in subway track lines is an important measure to solve the problem of vibration caused by subway trains.According to the different vibration isolators,the floating slab track bed can be divided into two categories: steel spring floating slab track bed and vibration damping pad track bed.The focus of this paper is to conduct in-depth research on the vibration-damping track bed.The main structure of the vibration-damping track bed is to lay a layer of vibration-damping pad under the track bed.On top of that,the effect of noise reduction and vibration isolation is produced.The material used for the vibration damping pad is not unique,usually it is a polymer material with certain stiffness and damping properties such as rubber or polyurethane.Therefore,a finite element model of the floating slab track bed with vibration damping pads is established in this paper,and a series of studies are carried out on the structure of the floating slab track bed with vibration damping pads from the perspectives of finite element dynamic analysis and dynamic analysis of the vehicle-rail rigid-flexible coupling system..The main research contents are as follows:1.The dynamic theory related to the orbital motion of the floating plate is expounded.First,it is introduced from the single-free dynamic vibration isolation system.Through the basic principle of D’Alembert,the differential equation of motion of the single-free vibration isolation system is deduced,and the single-free vibration isolation system is calculated.The general solution of the differential equation of the system of degrees of freedom,the general solution consists of two parts: steady-state response and transient response.By studying the power transmissibility of the single-degree-of-freedom system,it is found that when the excitation frequency is near the natural frequency of the system,it will cause the system to resonate,which does not play a role in reducing vibration,but has a negative impact.The realization process of the finite element method for three-dimensional dynamic problems is briefly introduced.Several main vibration evaluation indicators are expounded:vibration acceleration level,vibration velocity level,fourth-power vibration dose value VDV,perception KB.2.The finite element model of the track structure of the floating slab track bed with vibration damping pads is constructed.According to the vibration and vibration isolation theory of the single-degree-of-freedom system introduced above,the necessity of studying the natural vibration characteristics of the structure is pointed out,and the finite element analysis software is used.Modal analysis and harmonic response analysis were carried out on the model.Through modal analysis,the influence law of three track parameter changes on the natural frequency of the vibration damping track bed structure is obtained.Through the harmonic response analysis of the structure,the influence laws of three orbital parameter changes on the structure’s frequency response function are obtained.3.The dynamic simulation model of the vehicle-rail rigid-flexible coupling system is constructed by using the multi-rigid body dynamics software combined with the finite element analysis software.The train is simplified as a rigid body,and passes through the track and tunnel at a speed of 80km/h,and the system dynamics of the vibration-damping track bed and the ordinary integral track bed are compared and analyzed.The study found that compared with the common integral ballast bed,under common working conditions,the vibration reduction and isolation effect of the floating slab ballast bed with vibration damping pads can reach 12.91 dB.