Reasearch On Train-Induced Vibro-Acoustic Prediction Method And Control Strategy Of Long-Span Steel Bridge

As an economical,practical,efficient,and safe rapid rail transit mode,elevated bridges occupy an increasing proportion in urban rail transit.With the rapid development of elevated bridges,long-span elevated steel bridges have become increasingly popular among designers of long-span viaducts due to their strong spanning ability,good spatial integrity,high torsional stiffness and so on.Due to the continuous expansion of the city,the construction land in the city is very tight.Many long-span steel bridges have to be built directly beside the residential buildings,which lead to significant train-induced noise when the train passes the long-span steel bridge.The residents along the bridge are seriously disturbed by the train-induced noise.Chongqing Qiansimen Bridge is a typical case.The noise caused by the bridge is frequently complained by residents along the bridge.It can be seen that,for urban rail transit long-span steel bridges,it is of great theoretical significance and engineering value to propose a method for predicting the vibro-acoustic of the bridge structure,to establish a prediction model,and to discuss vibration and noise reduction control strategies.This dissertation has carried out a comprehensive sound and vibration prediction and control strategy research for the existing urban rail transit long-span steel truss cable-stayed bridge.The main work and results are as follows:(1)This dissertation su mmarizes the development status of long-span viaduct,points out the serious vibro-acoustic problem of long-span steel truss bridge,and puts forward the necessity of research.By referring to the relevant literatures at home and abroad,the research status of vibro-acoustic of train-induced long-span steel truss bridge and the research status of control strategy for vibration reduction track,polymeric damping materials are su mmarized systematically,which provides a direction for the research content and theoretical analysis method of this dissertation.(2)Based on the existing long-span steel truss cable-stayed bridge in urban rail transit,the field vibration and noise tests have been carried out firstly.The information and parameters of testing long-span steel truss cable-stayed bridge,running trains on the bridge and track structure are described in detail.The arrangement of vibration measuring points and noise measuring points on the bridge are described.The testing conditions,testing instruments and existing evaluation indexes and standards of vibration and noise are introduced.The vibration transfer law and noise radiation characteristics of the long-span steel truss cable-stayed bridge are analyzed from two aspects of time and frequency domain.(3)Considering the interaction of multiple wheelsets,the train,track and long-span steel truss cable-stayed bridge are reasonably simplified,and the vibro-acoustic prediction model of long-span steel truss girder is established based on the hybrid plate-beam finite element method and statistical energy analysis principles.The prediction model is verified based on the field measured data;from the four aspects of structural dynamic receptance,wheel-rail dynamic force,force transmission rate and force input to the bridge,this dissertation reveals the load transfer mechanism.The acoustic radiation efficiency and the important control parameters(modal density,internal loss factor and coupling loss factor)of the statistical energy model for the important acoustic radiation components of the long-span steel truss bridge are calculated.The distribution law of vibration energy,vibration velocity,acceleration and noise sound pressure of span steel truss girder is analyzed.The sound contribution rate of each component of the long-span steel truss girder is analyzed.(4)This dissertation introduces and simplifies the co mmonly used embedded sleeper track and vibration reduction track structure(trapezoidal sleeper,damping pad floating slab,steel spring floating slab)in viaduct of urban rail transit.The mechanism of vibration reduction and noise reduction for different vibration reduction track structures is studied.The influence of different vibration reduction track on the load transfer characteristics of long-span steel truss girder and the vibration energy input of steel girder members are discussed.The influence of vibration reduction track structure on the vibration velocity distribution characteristics and the noise distribution law of each field point of long-span steel truss girder are analyzed.The vibration and noise reduction effects of different vibration reduction tracks for long-span steel truss bridges are compared.(5)Based on the train-induced vibro-acoustic prediction model of long-span steel truss girder,comprehensive spectrum finite element method(SFEM)and statistical energy method,a sound and vibration prediction model of long-span steel truss girder with constrained polymer damping material(CPDM)was established.The influence mechanism on the important control parameters and the vibration and noise reduction effect of long-span steel truss girders with CPDM are analyzed in detail.The influence rule of CPDM with different parameters(damping layer thickness,constrained layer thickness,laying area,shear modulus of polymer material and constrained damping layer material)was deeply discussed.