| Steel bridges are widely used in rail transportation as the main type of bridge in China,and the noise problem of steel bridges is more serious than that of concrete bridges.Steel bridge has complex structure,and the study of noise problem is usually based on the vibro-acoustic characteristics of the slabs.However,the current research is very limited in terms of the vibroacoustic characteristics of orthotropic steel bridge decks.Under this background,this thesis carried out a series of studies of the vibro-acoustic characteristics of orthotropic steel bridge decks.Firstly,the research status of vibration and sound radiation of orthotropic steel bridge decks is summarized.Secondly,based on an in-situ hammer excitation test,the vibro-acoustic characteristics of orthotropic steel bridge decks are investigated,and the reliability of test data is validated by hybrid finite element and boundary element method.Thirdly,the free vibration of stiffened plates is derived by using the equivalent orthotropic plate method and the energy principle.Based on that,the vibration and sound radiation of the stiffened plate under fixed harmonic load are derived using the energy principle and Rayleigh integration.Furthermore,the numerical verification of the analytical results is carried out,and the effects of different load positions and boundary conditions on the vibration and noise of stiffened plates are discussed from the perspective of load and structure.Finally,based on actual engineering,the vibration and sound radiation of stiffened plates are analyzed in terms of parameters of plate stiffening direction,stiffener stiffness,U-rib thickness,U-rib spacing,two types of U-ribs and stiffener form.The main conclusions are as follows:(1)The hammer test shows that the vibration of top slab has no significant differences for the locations right above a U-rib and between neighboring U-ribs.The diaphragm can significantly reduce the vibration of stiffened plate.And the higher the frequency,the greater the vibration attenuation of the stiffened plate.(2)The equivalent orthotropic plate method to calculate the high-frequency vibration of orthotropic steel deck is not qualified due to low accuracy.Taking account of the eccentricity and torsional stiffness of the longitudinal U-ribs and transverse plate ribs,the energy method has relatively high accuracy,which is suitable for calculating local high-frequency vibration of the stiffened plate.Furthermore,the acoustic radiation response of stiffened plate obtained by Rayleigh integration is more accurate.(3)In three different boundary conditions,the vibration and noise of CCCC(four edges clamped)is the smallest,followed by SCSC(two opposite edges simply supported and two opposite edges clamped),and SSSS(four edges simply supported)is the largest.The results show that the vibro-acoustic radiation response of stiffeners decrease with the increase of boundary constraints.(4)The vibration and noise can be reduced by U-rib and plate rib,and the vibration reduction effect of U-rib stiffening plate in the high frequency part is more obvious.Compared with the oneway stiffeners,structure with longitudinal and transverse stiffeners has more significant effect on vibration and noise reduction.(5)The vibration noise of stiffeners can be significantly reduced,in a certain range,by increasing the flexural rigidity of U-ribs reasonably.However,the torsional rigidity of U-ribs has little effect on the vibro-acoustic characteristics of stiffeners.(6)The U-rib spacing and stiffener form are the two decisive factors for the sound radiation of stiffened slab.The sound and vibration characteristics of stiffened plate can be optimized by selecting U-rib stiffening and adjusting the U-rib spacing.However,the thickness of U-rib,large U-rib and UHPC layer have limited influence on the vibro-acoustic characteristics of stiffeners. |
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