Study On Noise Reduction Scheme Of Box Girder Structure Of High-speed Railway

At present,China has gradually mastered the high-speed railway construction standards with higher speed grades,and the requirements for environmental protection are more stringent on the premise of high standards.Bridges account for a very high proportion in high-speed railways,with the continuous improvement of speed grade,the dynamic interaction of vehicle-track-bridge is intensified,which leads to the more serious problem of vibration and sound radiation of bridge structure,and then affects the ride comfort of passengers and the living and office environment of residents along the line.In order to alleviate the influence of acoustic vibration of box girder bridge,it is necessary to study the noise reduction design scheme of box girder bridge.In this dissertation,based on vehicle-track-bridge coupling dynamics,combined with acoustic boundary element method and optimization algorithm,the vibration and sound radiation characteristics of box girder bridge caused by train running at high speed are accurately predicted firstly;Secondly,the most common single-track and double-track box girder bridges are taken as the research objects,and the advantages and disadvantages of acoustic vibration characteristics of the two box girder bridges are compared and analyzed,and the track type with strong acoustic radiation is taken as the subsequent optimization object;Then,the sound radiation contribution of different plates of box girder bridge is analyzed,and the design goal is selected for the subsequent noise reduction scheme;Finally,genetic algorithm is used to study the optimal thickness of each plate of box girder bridge,and the recommended value is given.The main research results are as follows:(1)The structural noise radiated by single-track and double-track box girder bridges mainly concentrates between 20 Hz and 80 Hz,with peak frequencies around 50 Hz and 30 Hz,respectively;In the sound field on the side of the bridge,the sound pressure of the two box girder bridges attenuates rapidly near their peak frequencies,and the sound pressure of the two box girder bridges attenuates faster than that of the double-track box girder bridge;Generally speaking,the acoustic radiation capacity of single-track box girder bridge is stronger than that of double-track box girder bridge.(2)The acoustic contribution of the top plate is the strongest among the single-track box girder bridges,so the related quantity of the top plate thickness of the box girder bridge is selected as the design objective in the subsequent noise reduction optimization scheme.(3)In this dissertation,genetic algorithm is used to optimize the noise reduction design of box girder bridge.Because the structure of box girder bridge is complex,in addition,there is a situation that multiple degrees of freedom reduce the calculation efficiency,therefore,this dissertation adopts the improvement measures of dynamic cross-factor and elite retention strategy in genetic algorithm,and the results show that the above improvement measures can improve the optimization ability.(4)Based on genetic algorithm,the thickness of top plate with the best acoustic radiation performance of single-track box girder bridge is 0.252 m,while the thickness of bottom plate and web plate has little change;The mass of box girder bridge increased by about 9%,the sound pressure level at the point decreased by about 4.8d B,and the peak frequency of sound power changed,but the optimized sound power value decreased compared with the initial value;The acoustic radiation cloud chart of box girder bridge is also improved compared with that before optimization,so ideal noise reduction effect can be obtained.