Characteristic and mechanism of structural acoustic radiation for box girder bridge in urban rail transit.

Noise caused by urban rail transit (URT) has been a hot concerned issue for a long time, and the secondary noise caused by viaduct bridges even make the problem more serious. As well known, structural acoustic radiation (SAR) induced by vibrations of concrete bridges is usually in low frequency. By now, the existing studies mainly focused on the noise above 20Hz, while the infrasonic wave below 20Hz attracts few investigations. However, it is more harmful to human according to relevant medical researches. Focusing on the viaduct bridges in a URT line laid with floating-slab track (FST), the characteristic and mechanism of SAR caused by box girder bridges are investigated in this paper. Primarily, a detailed train-FST-bridge dynamic interaction model is established, which is solved through an advanced mixed explicit-implicit integration method. Then, the SAR of the concerned bridge is analyzed adopting indirect boundary element method, including the infrasonic wave below 20Hz. And finally the mechanism of SAR is investigated based on the theories of structural vibration and acoustic. The conclusions provide theoretical foundation of vibration and noise reduction for viaduct bridges in URT systems.