Influence of Section Types on Noise from Elevated Rail Transit Lines

Simply-supported pre-stressed concrete bridges are widely adopted in urban elevated rail transit systems. The section types of the bridges not only affect bridge vibration and structural acoustic radiation, but also have an indirect influence on the propagation of wheel-rail noise. Thus, this work aims to provide guidelines on the selection of section types of bridges for low noise produced by elevated rail transit systems. The power flow method was first applied to obtain the spatially averaged vibration velocities of the rail and bridge considering wheel-rail interaction. The coupled finite-infinite element method was then used to analyze the generation and propagation of rail noise and bridge structural noise. The vibrations and noise radiation of the bridges of U-shaped girder, single-box single-cell box girder, and twin-box twin-cell box girder were compared. The results reveal that although the section types have a small effect on the vibration of the rails, they have large influence on rail noise radiation. Furthermore, both the vibration and structural noise of the bridges are significantly affected by the section types. In terms of rail noise, the U-shaped girder leads to 1-3 dB(A) lower rail noise level than the box girder. However, with respect to the bridge structure noise, the single-box single-cell box girder generates noise 2-10 dB(A) lower than the U-shaped girder, and the twin-box twin-cell box girder generates noise 2-6 dB(A) lower than the single-box single-cell box girder.