Vibration Noise Predicting Simply-Supported Box Girder Of High-Speed Railway Using Sea Method

As an important part of high-speed railway, bridge structures mainly adopt concrete box girder structures. Studies show that the secondary noise radiated from this structure gives priority to low frequency, so it inevitably influences the neighboring community life. Hence, it is of great significance to study the noise radiated from bridge structures vibration. By the essence, noise radiated from bridge structures is a problem of fluid-solid coupling, which is universally acknowledged by scholars of countries. At present, methods used to calculate structural noise include mainly the finite element method (FEM), boundary element method (BEM) and statistical energy analysis method (SEA), of which the former two methods are usually used together. But the efficacy of using the two methods to calculate structural noise is rather low and it could only predict noise radiated at low frequency. In view of this, this thesis adopts the method combing FEM and SEA to predict bridge structural noise and does the following work:(1) According to the basic principles of SEA, it analyses the transmit process of railway bridge power flow in the course of train passing. On this basis, it divides the 32m box girder into sub systems. Then, by the Thompson theoretical calculation modes about power flow and the Remington theoretical calculation modes about sound radiation, respectively, obtains the ralationship between the input power of bridge structure and the average vibration response of sub system, the ralationship between the average vibration response of sub system and the sound pressure level, thereby establishing SEA prediction model of bridge structure radiated noise(2) The 32m box girder mobility is very important to calculate the input power of bridge structures, while there are few studies on this aspect. Thus this thesis explains in a detailed way the mobility process through SEA and discusses the main factors which influence the structure mobility results. In view of few studies on box girder structure mobility both at home and abroad, this thesis put emphasis on the discussion of bridge structure mobility, giving a detailed introduction to the structure mobility calculation by means of FEM, and probing into the main elements that influences the outcome of structure mobility. (3) By taking advantage of the BDAP V2.0, a kind of bridge structure dynamics analysis software developed by Bridge Structure Vibration and Stability Lab of Southwest Jiaotong University, this thesis calculate the parameters i.e. rail vertical vibration speed and fastener contract pressure, needed in 32m box girder structure noise calculation. Besides, in order to make the results directly adoptable in SEA modes, MATLAB is made use of in analyzing and transforming the results.(4) By using SEA modes and taking advantage of MATLAB, this thesis calculates the noise radiated from 32m box girder, analyses the main parameters influencing bridge structural noise radiation, and puts up with some measures to reduce bridge structural noise.This thesis verifies the feasibility to pridict the bridge structural noise using SEA method, providing a reference for further bridge structural noise calculation.