Influence Of Different Track Structures On Vibration And Acoustic Radiation Characteristics Of Troughed Beam Bridges

With the urbanization advance of our country,the problem of traffic congestion will be more serious.In order to solve the problem of travelling conveniently and efficiently,the urban rail transit have built or planned to build in many cities.By the end of 2019,the total mileage of urban rail transit in our country has ranked first in the world.When the urban rail transit vehicles pass the elevated bridge line,the bridge body and the track structure on the bridge will have intense vibration and radiate the noise.The low frequency noise produced by its high frequency vibration has strong penetrability and slow attenuation.While long term exposure to such environment has many adverse effects on human health.Therefore,it leads to widely attention on the bridge structural noise problem of urban rail transit on domestic and foreign.The troughed beam bridge is widely used in the elevated line of urban rail transit because of its beautiful appearance,great safety protection and no cavity reverberation secondary noise hazard.Based on the vehicle-track-bridge interaction theory and the finite element-boundary element method,the acoustic and vibration characteristics of the troughed beam bridge in urban rail transit are studied.Based on the vehicle-track-bridge interaction theory and the finite element-boundary element method,the acoustic and vibration characteristics of the troughed beam bridge under the action of external incentive in urban rail transit are studied.With that,the acoustic and vibration characteristics of the troughed Beam bridge are analyzed by compared with the effects of high elastic fasteners,integrated ballast bed and rubber floating slab track.In addition,the webs on the troughed beam bridges have natural shielding effect on the sound radiation of the track structure on the bridge,so this dissertation has studied the sound radiation characteristics of the track structure on the troughed beam bridges.(1)The main frequency range of vibration-acoustic radiation on troughed beam bridges for urban rail transit is concentrated on the low-frequency noise range of 50-100 Hz.As the main contribution of vibration and acoustic radiation,the bottom slab should be studied firstly in the design of troughed beam bridge.(2)The acoustic radiation law of the troughed beam bridge of urban rail transit in the free acoustic field is uniform in the 0-20 Hz frequency band;in the 20-350 Hz frequency band,it shows that the acoustic radiation law is the interaction of web and the floor;in the350-500 Hz frequency band,it shows the complicated acoustic radiation law under the influence of local vibration.(3)High elastic fasteners can reduce the vibration response of the troughed beam bridge of urban rail transit to some extent,but have little influence on the sound radiation.The damping effect of rubber floating plate track is not only obvious,but also has great ability of noise-reducing.Compared with the integrated ballast bed,the rubber floating slab track can reduce the total sound pressure level by 7% at 10 m below the center line of the middle span of the troughed beam bridge.(4)The webs of troughed beam bridges of urban rail transit can obviously reduce the sound radiation of the track structure under the bridge within 20 meters,and slightly increase the sound radiation above the track structure.Therefore,the influence of webs’ shielding effect should be considered in the study of rail traffic sound radiation on troughed beam bridges.