| ABSTRACT:Along with the public convenience resulting from fast growth of the urban rail transit network, the metro-induced vibration and noise is more and more seriously concerned, as most of the metro lines pass under through densely inhabited district, adjacent buildings with sensitive instrumentations, and historic structures. Besides, the rail corrugation has been observed not only in curves, but also in some straight lines with vibration mitigation fasteners. Rail corrugation causes noise nuisance, and severe corrugation leads to damage to vehicle and track structure, even endangers metro operation.The metro-induced vibration can be seen as an integrated system, involving vehicle, track structure, track routes and vehicle speeds etc. The in-depth study on the dynamic characteristics of the track structure and the vibration mechanism of coupled vehicle&track is the foundation of the research on the metro-induced vibration and noise issues. A lot of field tests and research indicate that:the excessive vibration in variable-speed section and the rail corrugation in curved section are becoming more and more serious. However, few studies have been carried out on the dynamic behavior of the track structure under moving train with variable speeds and the curved track subjected to moving train.This Ph.D thesis is supported by the project of Natural Science Foundation of China named Research on the Prediction Models for Environmental Vibration Induced by Running Metro Trains (No.51008017), and Innovation Fund for Outstanding Ph.D students of Beijing Jiao tong University named Study on Analytical Model of Coupled Vehicle&Track with Variable Speeds (No.141067522) and Study on Analytical Model of Coupled Vehicle&Curved Track (No.2011YJS261). Based on the frequency-domain periodic analytical model of the track structure, the dynamic behavior of the vibration mitigation tracks were studied, combining with in situ hammer excitation tests and in situ vibration source tests carried out in Beijing Metro. And the frequency-domain analytical models of coupled vehicle&track in variable-speed and curved sections were firstly established, to study the influence of different parameters on the dynamic characteristics of the vibration mitigation track. The main conclusions include:(1) Based on the frequency-domain periodic analytical model of the track structure and in situ hammer excitation tests, the frequency response function of the track structure under unit impulse was calculated to analysis the dynamic behavior of track structure. The analytical study was also carried out to compare the dynamic behavior of vibration mitigation track with different parameters, including stiffness, damping of fasteners and support spacing, etc.(2) With in situ vibration source tests in Beijing Metro, the dynamic characteristics and vibration mitigation effects of different vibration mitigation tracks (Ⅲ-type vibration mitigation fastener, Vanguard fastener, Steel spring floating slab track, IV-type vibration mitigation fastener and Ladder track) were obtained. And it was also found that the rail/wheel resonance phenomenon around300-400Hz was the main generating cause for the rail corrugation initiation in the straight track with vibration mitigation fasteners.(3) The vibration responses of the track subjected to moving loads with variable speeds and the vibration responses of the curved track subjected to moving loads were determined analytically in the frequency domain. By adding the vehicle model, the frequency-domain analytical models of coupled vehicle&track in variable-speed and curved sections were established. The factors of a whole vehicle model, discrete supported track structure, track irregularity and wheel-rail Hertz contact were all taken into account. The whole solving process was based on analytical derivation and every physical quantity was represented by matrixes and vectors. The process was finished in the wave number-frequency domain, which provides great convenience for analyzing high-frequency dynamic interaction of vehicle and track.(4) A complete calculation program was established. Compared with in situ tests results, the calculated program was proved to be correct. Thereby, the calculation program can be used to study the problem of dynamic interaction of vehicle and track. Furthermore, the influence of different parameters (fastener stiffness, train acceleration, train initial speed and track radius) on the dynamic characteristics of the vibration mitigation track has also been presented here, providing theoretical support for the vibration mitigation and corrugation control in urban rail transit. |
PDF Full Text Request