Study On Underwater Vibration And Noise Characteristics Of River Crossing Bridges

With the development of transportation,there are more and more bridges across the river,and many of them pass through the national aquatic biological nature reserve.Aquatic organisms rely on sound signals to sense the external environment.The underwater radiation noise generated by vehicle induced bridge structure vibration will cause great interference to the transmission and reception of sound signals.In addition,excessive radiation noise will directly damage the hearing of aquatic organisms,resulting in temporary or even permanent hearing threshold shift.At present,the characteristics,radiation mechanism and influence range of underwater vibration and noise caused by bridges are not clear.In this context,based on a river crossing project,the underwater noise caused by vehicle induced bridge vibration during its operation is predicted and analyzed.The noise characteristics,propagation and attenuation laws of various sound sources are revealed.The research can provide a theoretical basis for the auditory protection of underwater endangered species.The main research work of this paper is as follows:(1)The three-dimensional dynamic numerical beam-element model based on Midas and the three-dimensional hybrid dynamic numerical model based on ANSYS are established.The modal analysis of the two models is conducted respectively,and the natural vibration characteristics of the bridge soil system are discussed.Then the effectiveness of the model is verified,which provides data support for subsequent research.(2)Based on the acoustic modal transfer vector method,the radiated noise of bridge tower and soil is predicted and analyzed.The random traffic flow model is generated,and the vehicle bridge coupling analysis is conducted based on the modal superposition method.The dynamic responses of bridge tower and soil structure under three random traffic flow conditions are obtained.Based on LMS Virtual.Lab,the three-dimensional bridge-soil-water-air coupling acoustic model is established.The modal displacement of the bridge tower soil structure is set as the coupling boundary between the acoustic grid and the structural grid.Then the acoustic modal transfer vector is obtained by using acoustic analysis.Combined with the acoustic mode transfer vector and vehicle bridge coupling vibration response,the radiated noise of bridge tower and soil is predicted.Based on the prediction results,the time-frequency characteristics and propagation law of radiated noise are preliminarily analyzed.(3)The radiation mechanism and characteristics of bridge underwater noise are investigated from two aspects: the spatial distribution characteristics of radiated noise and the contribution analysis of bridge tower and soil radiated noise.Plane and arc field points in all directions are set to obtain the cloud map of underwater noise sound field.Then the associated propagation and attenuation law is obtained to study the noise characteristics of different underwater areas.The sound pressure level of radiated noise of bridge tower and soil is calculated respectively,and the contribution of bridge tower radiated noise and foundation soil radiated noise to the total noise is investigated.