Research On Vibration And Sound Radiation Of A Steel-concrete Composite Box-girder Excited By Trains

In recent years,with the rapid development of China’s rail transportation and the improvement of bridge construction technology,steel bridges are increasingly used in bridge construction.The box-section composite beam bridges perform well in stiffness,stability and torsional stability.Therefore,this type of section is mainly used in rail transit composite bridge.Compared with concrete bridges,steel-concrete composite beam bridges result in serious noise problem,which is rarely discussed by existing literature.Under this background,this paper conducts an in-depth study on the vibration and noise of steel-concrete composite box-section beam while trains passing through.Firstly,the vehicle-track system coupling frequency domain analysis model is established to simulate the excitation generated when the train passes through the bridge.Secondly,the current vibration noise prediction methods of bridge structures are summarized,and a model suitable for full-band vibration noise prediction of steel box composite beams is proposed.Then,the reliability of the prediction model is verified based on the hammer test in which a steel box combined beam segment model is chosen as study object.Furthermore,combined with the vehicle-rail system coupling frequency domain analysis model,the validated prediction model is extended to a 40 m steel box coupling beam of a certain rail transit to predict the vibration and noise.Finally,based on practical engineering,the effects of track vibration reduction measures,as well as the structural parameters such as plate thickness,stiffening of plates and lateral connection system,on the vibration noise of steel box composite beams are analyzed,which provides a certain reference for the vibration reduction of this type of bridge.The main conclusions are as follows:(1)When the train passes through the bridge,the spectral characteristics of vibration and sound radiation of the structure mainly depends on the spectral characteristics of wheel-rail interaction force.(2)The noise propagation of the bridge structure is directional,resulting in:(1)the sound pressure level of a field point and the distance from the field point to the bridge structure are not monotonous;(2)all the vibration and noise reduction measures investigated in this study have different impact on spatial field points.(3)Elastic fasteners and steel spring floating slab tracks can effectively dissipate the vibration energy of the rails during the transmission to bridge deck,thereby the vibration sound radiation is reduced.For the total sound level within the scope of the sound field investigation of the midspan of the bridge,the noise reduction effects of 10.7 d B(A)and 39.2 ～ 50.1 d B(A)can be achieved by using elastic fasteners and steel spring floating slab tracks,respectively.(4)Plate thickness plays a certain role in the control of vibration and sound radiation.Under the premise of satisfying structural bearing capacity and reasonable project cost,properly increasing the thickness of the bridge deck can play a better role in reducing vibration and noise of steel-concrete composite box-girder.(5)Stiffening the web and reducing the spacing of diaphragms reduce vibration and noise by enhancing the local rigidity of plate and reducing the area of web.For the overall sound level within the sound field of the mid-span cross-section of the bridge,the noise reduction effect of1.4 ～ 2.8 d B(A)can be achieved by using web stiffening and reducing the spacing of the diaphragm.