Key Mechanism Research of Top Plate Thickening of the Box-Girder Bridge for Noise Reduction Design in High-Speed Railway

Abstract

In the context of noise reduction schemes for box-girder bridges (BGBs) used in high-speed railway, the thickened top plate design can effectively reduce the structural noise of the BGB, which has been widely recognized. However, it is difficult to obtain the optimum thickness of the top plate of the BGB without mastering the key mechanism of the noise reduction scheme. Therefore, this study took a 32 m simple-supported concrete BGB in the context of a high-speed railway as the research object and analyzed and compared the sound vibration characteristics of the entire thickened top plate versus the locally thickened top plate on BGB tracks, and the optimal noise reduction mechanism of the thickened top plate design scheme was studied in detail. The key issues of the thickened top plate noise reduction scheme are discussed. The results show that thickening the top plate can obviously reduce the bridge’s structural noise when subjected to severe vibration and high frequency bands because the vibration of the BGB is reduced. However, in the low frequency band, acoustic radiation can occur as a result of the small amplitude vibration, and this phenomenon is closely related to the vibrational distribution of the BGB. Therefore, it is necessary to focus on the vibrational distribution of the BGB as a priority when carrying out noise reduction using a thickened top plate. This paper points out the most significant factors affecting the acoustic radiation ability of the BGB in different frequency bands, especially the key problem of the strong acoustic radiation ability caused by small vibrations in low frequency band. The research results can provide an important theoretical basis for the optimal thickness design of the BGB.