| With the rapid development of economy and the increasingly convenience of traffics in our country,adverse effects of noise are becoming more and more serious.Bridge structure noise,as one of the most common,belongs to low frequency noise,which is lower than the sound human ear can perceive.It only shares little in the composition of traffic noise,while hazard to people's health.Steel is widely used in traffic construction,and the researches on the low-frequency noise of steel box girder bridge is few.To find out the law of acoustic field distribution under different working condition,and to seek a better way to reduce noise,it is necessary to make a study on the noise distribution of steel box girder bridge.In this paper,the common section steel box girder bridge is set as the research object.Through the establishment of finite element model under the software simulation analysis,the sound field distribution of steel box girder bridge under traffic load is done.The main research contents and results are as follows:(1)The current research background,the significance,the various environmental noise standard,the noise of the traffic line of classification and the harm of low-frequency noise brings are briefly introduced.Through consulting relevant literature both at home and abroad,the current topic research at present stage was review.The finite element method and boundary element method,statistical energy method and three kinds of numerical methods are emphatically introduced.(2)The amount of related basic acoustics was introduced,the basic characteristics of sound waves(acoustics reflection,interference of sound wave and superposition,sound wave diffraction)are summarized.Through joint waves continuity equation,motion equation and acoustic wave equation of state,made of acoustic wave equation is derived.(3)From the dynamic analysis of structures,a calculation method for the structural acoustic radiation are emphatically introduced,and briefly introducing the simulation of two kinds of finite element software ANSYS,the LMS.Virtual lab.The finite element model of steel box girder bridge was established.(4)The research object is 32 M constant section steel box girder,and the model is established by using the ANSYS software.through the way of loading on node,the dynamic response is calculated.After that,the dynamic response results are imported in the LMS software to analyze the sound field at different operating mode.In addition,the model in sound absorption materials are added and sound barrier is set to find out the factors and the relationship between the steel box girder bridge structure and these factor.(5)Sound field analysis it is concluded that the steel box girder vertical position and the same distance from the beam body location,box girder above sound pressure value is greater than the box girder under pressure value;At the bottom of the floor,from small to large change of the pressure from big to small sites sound pressure values are mainly concentrated in low-frequency sound segment between 20db-110 db.From the vehicle's speed impact on the steel box girder of the sound field distribution,the car speed,the greater the bridge of the radiation noise is larger and after the car off the bridge,the bridge will be in for a long time continuous vibration radiation noise.In the sites of the steel box girder of lateral surface acoustic field calculation and analysis,it is concluded that the lateral pressure values are mainly concentrated in 30db-92 db between low frequency band,the steel box girder roof after adding sound-absorbing material,sites of sound pressure value is not big,the noise reduction effect in general;After adding sound barriers on both sides of steel box girder of steel box girder above sound field has strengthening effect,for steel box girder and the distance below sound field has no obvious effect of noise reduction,sound barriers to close to the foreign sound field has more significant noise reduction effect. |
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