Measurement research on vibro-acoustic characteristics of large-span plate-truss composite bridge in urban rail transit

Abstract

Large-span plate-truss composite bridge (LPCB) is developing more and more rapidly in urban rail transit. Nevertheless, the bridges are often close to residential buildings, and some even pass through residential areas directly. Compared with small span bridges and ordinary concrete viaducts, the train-induced vibration and noise of LPCB are larger and last longer, and have a greater impact on the residents along the line. Therefore, it is necessary to study the train-induced vibro-acoustic characteristics of LPCB. However, the current research on LPCB mainly focuses on the aspects of bridge structure design, construction, traffic safety and comfortable capability etc, and usually only cares about the global mechanical behavior of bridge structure and train-track-bridge coupling vibration. In order to study the vibro-acoustic characteristics of large-span and complex bridge structures such as LPCB, it is extremely important to obtain and analyze the field measured data. In this paper, the vibration and noise filed measurement of LPCB has been carried out by the authors. The vibration characteristics of track and bridge system have been measured by means of acceleration sensors, which were arranged on the rails, track slab, the center of bridge deck, longitudinal web and transverse web. The noise characteristics of wheel-rail and bridge structure system have been measured by mans of noise sensors, which were arranged beside the track structure and under the bridge structure. Based on the measurement date, the vibro-acoustic characteristic of the LPCB were analyzed in the present paper. It is found that the response of track structures are mainly affected by wheelsets periodic excitation, while the response of bridge structures are determined both by wheelsets periodic excitation and wheel-rail irregularity; the rail and slab are decoupled after beyond the natural frequency of the rail-fastener system (100 Hz); the vibration energy in high frequency band can be effectively suppressed to downward transmission by damping pad floating slab track; the overall vibration level of rail, track slab and bridge are about 130 dB, 114 dB and 118 dB respectively, the overall sound pressure level of track-side and bridge structure are approximately 82 dB(A) and 83 dB(A) respectively.