Dynamic Analysis And Vibration Reduction Research Of Urban Rail Transit Viaduct With Ladder Track

In recent years, the rapid development of urban rail transit (URT) system brings traveling convenience to people, while at the same time, causes some new problems. With the cooperation of urban rail transit in large area in Beijing, the URT lines go through the busy districts in downtown and residential areas. The vibrations and noises induced by running trains are exerting a great influence on people’s living and working environment.The ladder track is the second-generation floating slab track featured with low noise and low vibration. It can not only exert the inherent properties of sleepers, enhance the ability to distribute the load significantly as a sleeper, but also supply the stiffness and mass to the rail. Therefore, it is an ideal track for vibration reduction which can increase the bending and shearing rigidity as well as has suitable mass.The vibration properties and reduction effects of ladder track is studied in this paper, through theoretical analysis, numerical simulation and experimental research. The main contents and results are as follows:1. The development trend and current researches of urban rail transit are reviewed according to the related references of international and domestic experts, based on which the environment vibration problems caused by urban rail transit and the related vibration reduction measures are summarized.2. The dynamic characteristics of ladder track are studied by using the finite element method. By changing the unit length of ladder sleeper, the stiffness and spacing of sleeper bearings and the stiffness of rail pads, the natural frequencies and mode shapes of ladder sleeper are studied. Moreover, the dynamic loading and hammer impact tests were conducted on a ladder track unit in laboratory and the measured results are analyzed.3. The track irregularities of ladder track and common slab track were measured at the elevated bridge trial section on Beijing metro Line5. Based on data analysis, the power spectrum densities of the track irregularity are obtained. The empirical spectrum formulas are proposed by fitting the measured data and revising the existing empirical formula, which can give reference to dynamic analysis of train-track-bridge system.4. The dynamic experiments were carried out at the trial section with the ladder track on Beijing URT Line5, and the experimental results are fully analyzed. The vibration reduction effect of the ladder track is obtained which can be used for verifying the correctness of the train-ladder track-viaduct FE model.5. The train-ladder track-bridge dynamic interaction model is established by coupling the separated track subsystem with the train and the bridge subsystems, and the computer simulation program is worked out. By changing the parameters of the train and the track structures, the dynamic responses of the train, the track and the bridge are obtained by computer simulation, based on which the vibration transmission rules are also obtained.