Prediction Of Structural Noise Field Of U-beams And Design Optimization Study On Intercity Railways

In recent years,as the scale of China’s urban agglomerations has continued to expand,intercity railways have developed rapidly.U-beam has low building height,convenient construction and low cost as a relatively new form of bridge structure.It has broad application prospects in intercity railways.However,the U-beam has a light weight and a small structural rigidity,which makes the structural noise problem more significant.This dissertation took the U-shaped beam of the intercity railway as the research object,discuss the structural noise influence of the U-beam under the dynamic load of the train.The main work of the dissertation are followed:(1)This paper drew the research focus of this dissertation—the structural noise of U-beams by reviewing the development status of inter-city railways in China and analyzing the noise sources of inter-city railways.Secondly,The research status of bridge structural noises and the control measures of bridge structural noises were summarized.The boundary element method should be used to calculate the U-beam structure noise.(2)The train-bridge system was analyzed through inter system iteration method,which calculated the dynamic responses of the bridge.The local vibration effect of the U-shaped beam was obvious and the dynamic response of the bottom plate was large.(3)The prediction model of U-beam structural radiation noises was established.In the model,the bridge vibration responses obtained from train-bridge coupling system analysis were used as the boundary condition.By means of indirect boundary element method,the structural vibration noises can be predicted.The distribution regularity and influence factor of the structural noise and the sound pressure contribution of each elements were analyzed.The influence of train speeds and ground reflection on the structure-borne noise were discussed.The sound pressure contribution of each element was calculated.The structural noises of U-beam mainly in the range between 20Hz-200 Hz.The noise distribution was infected by noises in low frequencies a lot.The base plate contributed more to the sound pressure at the field point than the web and the flange plate.(4)In order to reduce the structural noises of U-beam,this dissertation discussesd the influence of section parameters,material parameters and boundary conditions on U-beam structure noise based on the established U-beam structure noise prediction model.The increase in the thickness of the bottom plate and the web can reduce the overall sound pressure level at the field point and the influence of the bottom plate is more significant.The increase in the height of the web changes the angle of propagation of the noise and the total sound pressure level at the field point decreases.The rib reinforcement of the web can reduce the total sound pressure level of the field point and the degree of influence is limited.The increase in stiffness can significantly reduce the total sound pressure level at the field point when the bridge stiffness is small.The increase of the damping ratio can reduce the total sound pressure level of the field point and the degree of influence decreases as the damping ratio increases.The increase in the stiffness of the rail fastener causes the total sound pressure level of the field point to increase first and then decrease.The total sound pressure level of the field point can be reduced by using fixed support constraint at both ends of the U-beam.