| With the increasing of train speed,the influence of railway operation on surrounding environment increases gradually,especially the influence of noises induced by trains running.How to deal with the noise pollution become to be the key issue of high-speed-railway design and construction.Trough girder has low building height,beauty configuration and nature barrier of noise.In consideration of these advantages,the trough girder is considered as a special environmental bridge girder type.This dissertation took simply supported trough girder of high-speed-railway as the study object,discussed the dynamic performance and noise influence of the trough girder with high speed trains passing through by means of theoretic and experimental analysis.The main works of the dissertation are followed:(1)The engineering application of concrete trough beams was introduced,the research status of bridge structure-borne noises and wheel-rail noises were reviewed.(2)The train-bridge dynamic coupling model with trough beam was established.Based on multi-body assumption,the motion equation with 19 Dofs of the train was set up.The bridge model was established with shell elements by FEM software ANSYS.The relationship of wheel-track took different assumptions,which were linear creeping slip on the horizontal direction and direct connection on the vertical direction.The train-bridge system was analyzed through inter system iteration method,which calculated the dynamic responses of the bridge and trains separately.A simply supported trough beam bridge with 32 m span was taken as an example.With the train speed changing from 160 km/h to 375 km/h,the dynamic responses of the system were analyzed and all the dynamic indexes of both trains and bridge were under the limit values.(3)The domestic and overseas railway noise evaluation methods were summarized and the prediction model of trough beam structure-borne noises was established.In the model,the bridge vibration responses obtained from train-bridge coupling system analysis were used as the boundary condition.By means of indirect boundary element method based on Helmholtz functions,the structure-borne noises can be predicted.A simply supported trough beam bridge with 32 m span was taken as an example.The distribution regularity of structure-borne noises of trough beam was analyzed.The influences of train speeds,ground reflection and piers heights on the structure-borne noise were discussed.The sound pressure contribution of each element was calculated.The structure-borne noise of concrete was mainly in the range under 200 Hz.The noise distribution was infected by noises in low frequencies a lot.Structure-borne noise of trough beam was lager than that of box beam.(4)The capture-effect of the trough beam on wheel-rail noise was analyzed.Firstly,the sound radiation model of wheel-rail noise was established.The surface roughness of the wheel and rail was used as the excitation.Considering wheel/rail contact area filtering,based on train-track-bridge coupling dynamic theory,together with pseudo excitation method,the wheel-rail rolling noise could be predicted.Taking the calculated wheel-rail rolling noises as the sound source,a 2D boundary element model was set up,and then the capture-effect of the web on wheel-rail noises was studied and compared with the results of box beam.The influences of ground reflection and pier height were discussed.Compared with the results of simply supported box beam bridge with 32 m span,the capture-effect of the trough beam was remarkable.The sound pressure level beside the beam of the trough beam was all smaller than that of the box beam in all frequencies.(5)A simply supported trough beam bridge with 32 m span was taken as study object.The influences of the thickness of the plate(web and bottom plate)and the stiffness of the web on the structure-borne noise of the trough beam were discussed.The effects of the web height and web dip angle on capture-effect of wheel-rail noise were analyzed as well.With the increasing of web thickness,the overall sound pressure level of field points increased as well and the increment decreased gradually.With the increasing of bottom plate thickness,the overall sound pressure level of field points decreased gradually and the decrement increased obviously.Stiffed web can reduce the sound pressure level of sound field points around the trough beam.The reduction value was not large,about 0.4dB miner than normal web.The sensitivities of sound pressure level of field points in different region on the angle and height of web were different.Based on low noise design principle,the proper angle and height of the web should be adopted according to the location of main sound points.(6)Simply supported trough beam and box beam bridges with 32 m span were taken as study objects.In-situ experiments were carried out to discuss the noise performance of the two beam types.The structure vibration of the bridges with trains passing through on different speeds was measured.The noise in near field and far field was recorded as well.The experiments were used to verify the theory analysis.The influences of the two beam types on train noise were compared.Comparing the theoretical and experimental results of the vibration accelerations and the structure-borne noises of beam bottom plate,the results showed that the experimental values fitted well with the theoretical ones.The dominant frequency of structure-borne noise of trough beam was between 40?80 Hz and the peak value of the sound pressure appeared on 40 Hz which was corresponded with the peak value frequency of beam vibration.Without the consideration of low frequency noises,the trough beam had better noise reduction effect than the box beam. |
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