| With rapid development of city scale, the urban rail transit (URT) becomes an important public transport. However, the vibration and noise caused by URT have serious influence on people's daily work and life. The elevated structure is an important component of this system, and its influence on the surrounding environment is concerned by more and more people.In this paper, study is made of the mechanism of structural vibration and noise caused by URT train, the distribution and characteristics of vibration and noise in different elevated structures, and the spatial distribution and propagation of noise inside vehicles, station halls and around elevated structure lines, by means of theoretical analysis, numerical calculation and filed experiment. The main research contents and results are as follows:1. A finite element model of three-span continuous beam with moving loads is established by ANSYS to calculate the displacement and acceleration responses of the bridge. The experiment results show that the calculated data is close to the measured data.2. A2-D finite element model of sound field is established by ANSYS. The fluid unit FLUID29is used to simulate the air field area around the structure, and the air-absorption fluid unit FLUID129to establish the boundary. The sound pressure change process at the bottom of beam, the1/3octave sound pressure and the sound pressure distribution of sound field of the middle cross-sections of each span are calculated. Based on the weighted sound pressure evaluation system, the contours of sound pressure are drawn and used in the analysis of noise radiation attenuation.3. To study the relationship of vibration and noise, an acoustic transfer vector is derived to contact the vibration acceleration with the acoustic radiation pressure by combining the finite element method with the boundary element method. By using the vector, the sound pressure can be directly estimated at any point in the sound field by structural surface vibration acceleration. The method may avoid the shortcomings of higher computational complexity and long time calculating in finite element analysis, and may solve the problem of non-uniqueness in characteristic frequency and singular integral or hypersingular integral in boundary element analysis. Finally, the experiment certificated that noise prediction with acoustic transfer vector has good accuracy. 4. By changing damping, stiffness, mass, support stiffness of the bridge, and vehicle speed, load, train formation and traffic in two directions, the dynamic responses of the bridge and the radiation pressure level are calculated. The results show that reasonable parameters adoption of bridge structure and control of vehicle state may effectively reduce structural vibration and noise levels.5. An in-site test was conducted on the elevated bridge test section of Beijing Metro Line5. The reduction effects of vibration and noise were measured and compared when trains ran on the ladder sleeper track and the common track. Based on the test data, the noise attenuation laws within a certain range of around the bridge, a prediction model for noise radiation is proposed. Another in-site test was conducted at a viaduct section of the Airport Express, by which the vibration and radiation noise levels in different parts of box girder structure were measured when a linear motor vehicle passed by. In addition, the coherence of vibration and noise spectra are studied.6. A survey of noise condition inside Beijing URT station halls was carried out, in which the noise characteristics in underground, ground and elevated stations were measured and compared, and the effects of different measures for reducing vibration and noise are analyzed. The noise was measured in the waiting area of Beijing South Railway Station. The noise levels were measured at different floors of a6-story building near a URT bridge.
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