Analysis Of Acoustic Radiation From Reinforced Concrete Cylindrical Shell

Urban rail transit, which is one kind of safety, comfortable, on time, rapid and large-capacity means of transportation, has got rapidly development in our country in recently years. Urban rail transit has been beneficial for people to go out to travel conveniently, while it has also brought about some negative effect for the urban environment such as noise, vibration, electromagnetic radiation, etc. The main influence which urban rail transit has brought about is the noise and vibration during operating period, which disturbed the people who living beside the line. The noise generated by the vibration of viaduct box is mainly low-frequency noise. Research show that, people may suffer organic damage if they bear the low-frequency noise in a long time. Therefore, the research on the structure noise of box has important significance in lowering vibration, reducing noise and promoting the healthy development of rail transit.In this study, the acoustic radiation characteristic of the reinforced concrete cylindrical shell with stiffened ring ribs is analysed, which is simply supported and submerged in air. The main purpose of this study is to do further research on the vibration and radiation of the box girder, which used in urban rail transit, and provide solution to its noise and vibration control. The main contents of this study can be summarized as follows:1. According to the theory of shell's vibration and acoustic finite element of ANSYS established fluid-structure coupled model of reinforced concrete cylindrical shell with and without stiffened ring ribs. Calculate the external acoustic radiation characteristic of the shell under harmonic load.2. Analysed the impact of internal air over the acoustic radiation characteristic of the cylindrical shell, which with and without ring ribs. And draw in the low-frequency range, the impact of internal air over the external shell's acoustic radiation characteristic is very small. The effect of the internal air can be neglected.3. The impact of ring ribs over the acoustic radiation characteristic of the cylindrical is analysed. And draw the conclusion that the ring rib has much effect on acoustic radiation characteristic of cylindrical shell, and in the major frequency range which has been calculated. Add ring ribs inside of the cylindrical shell can effectively reduce sound pressure level of the structure.4. The effect of distance and height of the ring ribs over the acoustic radiation characteristic of the shell has been analysed. And the result shows that increase the height of the ring rib, and decrease the distance of the ring ribs can reduce systematic sound pressure level.At last, base on the summary of the whole content, and provided the problems which need further study.