Effect of web hole on vibration and noise of rail transit box girder

The vibration and near field noise of each plate of a simply-supported box girder in the urban rail transit were measured, and the relationship between the vibration radiation noise of box girder structure and the box girder vibration was studied by combining with the acoustic radiation theory of plate. Based on the low-frequency characteristics of easily generating diffraction of box girder structure noise, the structure noise change situations of rectangular concrete plates under different opening conditions were calculated. On the basis of considering the web holes of box girder, the vehicle-track-box girder coupled finite element model and the box girder vibration-structure noise finite element-infinite element model were built. The vibration and structure radiation noise change situations of each plate before and after the opening of box girder web were analyzed. Research result shows that the acoustic radiation efficiency of box girder plate does not show a linear relationship with the increase of frequency. The near field low-frequency (less than 250 Hz) radiation noise of each box girder plate is not a simple linear relationship with the structure vibration acceleration level. The noise radiated by the box girder is determined by the vibration of box girder and the acoustic radiation efficiency of each box girder plate together. For an opening plate simply supported at both ends, when the opening ratio is basically the same (about 0.4%), the smaller the diameter of opening hole, the smaller the sound pressure level of plate vibration radiation noise is. Using the finite element-infinite element method to simulate the near field low-frequency noise of box girder structure can solve the influence of sound field boundary when using the finite element method only, and can avoid the inconvenience caused by the cross-use of multi-software in the finite element-boundary element method. Although the web hole increases the vibration response of box girder plate at some frequencies (100-125 Hz), the acoustic radiation efficiency of plate and the noise in corresponding frequency band range reduces, due to the connection of inside and external sound fields of box girder increasing the acoustic short circuit effect. After the opening of web, the total sound pressure levels near the top plate, bottom plate and web plate in the frequency band of 1-250 Hz reduce by 9.43, 2.74 and 1.63 dB, respectively. Thus, the box girder structure noise is controlled. 3 tabs, 23 figs, 30 refs. © 2019, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.