Comparison of vibration and noise characteristics of urban rail transit bridges with box-girder and U-shaped sections

Abstract

Rolling noise and structure-borne noise from rail transit viaducts often lead to complaints from nearby residents. Concrete box section bridges are commonly adopted for the viaducts but those with U-shaped sections have become popular recently due to their more attractive form and reduced visual impact. One question that often arises in relation to the choice of the section types is their relative noise performance. This study aims to compare the vibration and noise characteristics of concrete bridges with different sections in a systematic way by using the same noise prediction method. A coupled track-bridge model is introduced to obtain the rail vibration and the power input to the bridge through the rail fasteners. A three-dimensional vibro-acoustic finite element method is applied to obtain the noise radiated from the bridge and the rail subjected to sets of multiple forces acting on them. This is determined in terms of the radiation efficiency and sound pressure transfer functions for arbitrary forcing. The averaged mean squared vibration velocity of the coupled wheel-track-bridge model subjected to roughness excitation is used to scale the noise from the acoustic model. The method is validated by comparison with field measurements of noise from a U-shaped bridge in Shanghai. Comparative investigations are then conducted of the U-shaped bridge, a box girder bridge with single cell and a twin-box girder bridge with two cells; each is fitted with equivalent noise barriers. It is found in each case that the noise from the rail is about 10 dB(A) larger than the bridge noise at positions to the side of the bridge. The U-shaped girder generally leads to slightly lower total noise levels than the box girders, with differences of less than 1 dB(A) when they have noise barriers of the same height. In terms of the bridge noise, however, the single-box and twin-box girders produce an average of 8.6 and 11.7 dB(A) less noise than the U-shaped girder.