Research On Environmental Noise Characteristics And Control Of Urban Rail Transit Elevated Line Based On Isosurface Principle

Taking urban rail transit noise as the main object of study,the wheel-rail noise and bridge secondary structure noise are studied,and the characteristics of noise isosurface are explored.It is found that the area above the noise isosurface is the wheel-rail noise control area and the area below is the bridge secondary structure noise control area.Considering the characteristics of bridge secondary structure noise,such as low frequency noise,long transmission distance,strong transmission force and slow attenuation rate,the control area of bridge structural noise should be as small as possible in practical engineering,that is,the position of noise isosurface should be reduced.In order to study the related characteristics,first of all,on the basis of finite element theory,using the multi-body dynamics for the coupled model is established in this paper,the dynamic response of box bridge rail system has carried on the correlation analysis,secondly analyzes the different fastener stiffness and damping pad surface stiffness under elevated line environmental noise and the influence of vertical acoustic barrier to noise.The results are as follows: Secondly,the environmental noise of the elevated line under different coupler stiffness and different damping pad stiffness is analyzed.The results show that:1.The model calculation results are in good agreement with the field test results,thus confirming the accuracy of the model established in this paper;2.When the vertical stiffness of the coupler increases,the dynamic response of the rail decreases obviously,and the dynamic response of the track plate increases obviously,but the amplitude of the vibration response of the bridge almost does not change.When the stiffness of the coupler increases,the wheel-rail noise decreases continuously,and the noise of the bridge secondary structure does not change significantly.With the increase of the stiffness of the coupler,the contour surface of the wheel-rail noise and the bridge secondary structure noise at the frequency of 50 Hz generally shows a gradual increase.Therefore,the coupler with smaller vertical stiffness should be selected as the vibration and noise reduction measure of the elevated line of urban rail transit.3.When the stiffness of the damping pad increases,the vibration response of the rail and track plate decreases,and the vibration response of the bridge increases.The linear total sound pressure level of wheel/rail noise decreases as the stiffness of damping pad increases.On the contrary,the noise of bridge structure is increasing.With the increase of the stiffness of the damping pad,the position of the isosurface is constantly rising.This is because the increase of the stiffness of the damping pad makes the noise of the bridge structure increase and the noise of the wheel and rail decrease.Therefore,when noise reduction is carried out on the elevated lines of urban rail transit,the stiffness of vibration damping pad should be smaller.4.The influence of vertical sound barrier on isosurface position is analyzed.