Analysis On Noise And Noise Reduction Measures Of U-beam Of Urban Rail Transit

Urban development and social progress are inseparable from the promotion of urban rail transit.Nevertheless,the following traffic noise has become an important environmental pollution problem.In recent years,the Ministry of ecology and environment has revised the noise pollution prevention and control law on this issue,brought the urban rail transit noise into the scope of noise prevention and control,and gradually improved the transportation noise pollution prevention and control system.As a new type of beam,U-beam is gradually popularized and used.Its web can block the radiation noise of rail noise and has a certain shielding effect on rail noise of wheels.It is an effective measure to control the noise of rail from the source of noise.In the article,the dynamic characteristics,structural radiation noise and rail noise of wheel of simply supported U-beam in the East extension section of Nanjing Line 2 are experimentally explored and theoretically analyzed.At the same time,the vibration and noise reduction effect of installing the new track damping damper on the track structure and the influence of installing the sound barrier above the web on the noise of sound pressure level at the rail side is quantitatively analyzed.The main contents include:(1)This paper discusses the influence of noise pollution in the development of urban rail transit and the application of concrete U-beam,and summarizes the research status,existing problems and control methods of structure noise of bridge and rail noise of wheels.(2)Compare the noise emission and prevention standards of different countries,study the similarities and differences of noise standards,verify the calculation methods through experiments,and put forward reasonable environmental protection design objectives to solve the problems caused by noise pollution.(3)The field noise performance test of 25 m simply supported U-beam of urban rail transit is carried out to test the vibration and noise the law of the body of beam before and after installing the damper on the rail.Compare the vibration level and sound pressure level of the beam before and after the installation of damping,and analyze the vibration and noise reduction effect of the damper.The results show that the damper has the obvious effect on the vibration and noise of 50 Hz ～ 200 Hz,and the vibration and noise reduction effect of the bottom plate which is higher than that of the web.On the beam side,according to the noise test point distribution standard,the radiation law and noise reduction effect of the noise of beam side before and after the installation of the damper is compared.The results show that the damper has the obvious effect in the low frequency band(250Hz～630Hz),and there is no obvious effect in the high frequency band due to energy attenuation.(4)Based on the vehicle line bridge coupling theory,a 25 m concrete simply supported U-beam is established by using ANSYS finite element software,and the dynamic response of the U-beam is analyzed when the vehicle speed is 80 km / h.Then,based on the model of noise calculation of U-beam,taking the response analyzed by the finite element model as the input condition,combined with the acoustic boundary element method of indirect,the structural noise of U-beam is further analyzed,and the sound pressure level of structural noise is analyzed.The results show that the sound pressure level of the bottom plate of the mid span section is larger directly below and above,and the sound pressure level of the sound field on both sides of the web is smaller.Considering the effect of ground reflection,the closer to the ground,the sound pressure level of the field of reflected sound is larger.(5)The calculation method of sound source of noise of wheel rail is studied,and the influence of ground reflection is considered.The wheel rail noise sound source is back calculated according to the test results,and then the results of back calculation of sound source are verified.The results show that this method is effective in calculating the sound field of noise of wheel rail;due to the shielding effect of the web of the U-beam,which the distribution trend of the noise is mainly above the U-beam,and the sound pressure levels on both sides of the web are small.The installation of vertical sound barrier at the web of U-beam can effectively reduce the noise of wheel rail generated by vehicles.The research shows that the vertical sound barrier can effectively reduce the high frequency of noise of wheel rail,and the closer to the track,the better the noise reduction effect.