Vibro-acoustic Characteristics and Influence Factors of a Steel Box Girder

To study the vibro-acoustic characteristics of steel box girders, hammering tests and statistical energy analysis (SEA) were jointly introduced to investigate the SEA parameters and vibro-acoustic responses. First, based on a steel box-girder section (10.1 m (length)×4.8 m (width)×3.1 m (height)), the acceleration frequency response functions of the top and bottom slabs at different locations were measured by applying hammer excitations. Second, an SEA model was built to predict the vibro-acoustics of the steel box girder, in which the modal numbers of different slabs in the frequency range of 100-5 000 Hz were investigated. The prediction model was validated by comparing the simulation results with the hammering test data for the acceleration frequency response functions. Finally, based on numerical simulations, the variations in the SEA parameters and vibro-acoustic responses were investigated for different structural design parameters (e.g., stiffening rib and diaphragm). The research results show that the acceleration frequency response functions of the top and bottom slabs at different locations are close to each other, except in certain frequency bands. The SEA prediction method is highly accurate, while its computational efficiency is low compared with that of the finite-element method. By introducing stiffening ribs, the modal density and input power of the slabs, as well as the degree of coupling between subsystems, are reduced; however, the radiation efficiency of slabs is increased. The vibration velocity levels of the top and bottom slabs at each frequency band decreased on average by 8.2 and 6.7 dB, respectively. The sound power level of the steel box girder is reduced by 3.1 dB(A) on average at each frequency band. The influence of stiffener spacing on the vibro-acoustic responses of the steel box girder is greater than that of the stiffener thickness. Thus, the stiffener spacing should be preferentially regarded as the main parameter when conducting acoustic optimization. The diaphragm can reduce the vibration response of the steel box girder to some extent. The sound power level of the steel box girder can be increased by 1.3 dB(A) on average at each frequency band once the diaphragms are removed. © 2021, Editorial Department of China Journal of Highway and Transport. All right reserved.