Studies On U-Shaped Beam Structure Noise And Shadowing Effect On Wheel-Rail Noise

Among all types of noises generated by trains passing across the viaduct, two of them arouse more and more attentions:the wheel-rail noise, mainly consisting of mid-frequency and high-frequency noise, and the bridge-borne noise, which is formed largely by low-frequency noise. Due to the features of the slow recession and long-spread distance possessed by the low-frequency structure noise, the study of U-shaped beam structure noise becomes rather important.On the other hand, along with the rapid development of the application of U-shaped beam structure on the high-speed railway and urban mass transit, it is of great significance to study the shadow effects on wheel-rail noises produced on the U-shaped beam structure, which have been done very few both domestic and abroad nowadays. The method of studying noise barrier can be used reference in this study, measuring its ability of reducing noises by calculating the insertion loss according to the boundary element theory.This thesis contains two parts. Firstly, by approaches of coupled vibration theory and boundary element theory, the vibration caused by trains and the radiation of low-frequency noise on the U-shaped beam structure are discussed. Secondly, the shadow effects produced by U-shaped beam structure and its ability of reducing noises are evaluated. The main contents are as follows:1) This thesis begins with the review of the research status of coupled vibration, mainly are done by field test method and model test method. The methods used in bridge-borne noise research includes finite element method, boundary element method, energy method and so forth. Comparing the three methods above, coupled vibration theory and boundary element method are chosen to study the U-shaped beam structure noise.2) Adopting coupled vibration theory and boundary element method, and taking the U-shaped beam structure as a research object, the vibration caused by trains and the radiation of low-frequency noise are discussed.3) Still focusing on the U-shaped beam structure, the shadow effect produced by U-shaped beam structure and its ability of reducing noises are evaluated. Then, the shadow effect on wheel-rail noise of U-shaped beam structure are analyzed by comparing with that of box girder. Last but not least, the parameters, such as the loudness of the sound source, the length of the flange, and the width of the web, which affect the shadow effect are analyzed.