The Prediction Model And Analysis Of Wheel-rail Noise Of Elevated Rail

With the rapid development of urban rail transit in China, control post-constructionsettlement of subgrade, foundation condition, saving land, engineering cost, environmentalprotection and other factors to consider, high-speed railway and urban rail mostly adopts thestrategy of "way to bridge the generation",elevated rail proportion become bigger and bigger.Compared with the road line, the noise level increase2~20dBA when trains are runningthrough elevated line on both sides of road. As an important hub of the urban traffic, theelevated rail transit mostly through or located in the city center area, the impact of wheel/railnoise, traffic noise and the vibration noise of bridge structure on people’s life is becomingmore and more big, people and research scholars pay attention to it. Elevated rail’s wheel-railnoise as the main noise, so it is necessary to study the elevated rail’s wheel-rail noise.The noise’s direct causes is vibration characteristics of wheel-rail system, analysis of trackstructure’s vibration is the premise to predict the wheel-rail noise, this paper use the mobilityof track structure as indicators to analysis the structural vibration, into comparison,using theanalytical method and the finite element method to analysis the mobility of elevated tracksystem, based on this, establish the wheel-rail noise prediction model to predict the elevatedrail wheel-rail noise. The research content and the main conclusions are as following:(1) Establish the analytical beam model and finite element model of the viaduct,analysis of two kinds of models’ reliability, below13Hz, the amplitude ratio of thebeam model is slightly larger than finite element model, the trend almost the same. Above13Hz, the vibration amplitude of finite element model is significantly higher than the beammodel, the amplitude of beam model is attenuation rapidly, and the finite element modelof attenuation is not obvious, beam model is no longer reflected box girder. Thus, using thefinite element method is more suitable.(2) Analyzing the vibration characteristics of box beam and U beam incomparative, obtained that in the low frequency band vertical vibration affected by the sectionshape of bridge, vibration of U beam was significantly higher than that of the box sectionbeam, in tens of Hz to a few hundred Hz band, section shape’s influence onthe bridge vibration is little; Bridge bracing stiffness’s effect to the bridge structure’svibration mainly focus below200Hz.(3) Establishing the finite element model of elevated rail system is to analysis thevibration characteristics of elevated rail system, the results show that the vibrationof viaduct structure appear the first-order peak at6Hz,corresponding to the natural frequency of the viaduct; In200Hz, appeared the second-order peak, corresponding to the properfrequency of the steel rail fastener.(4)The effect of viaduct foundation structure form to elevated track structure’svibration is mainly below20Hz, on this band, elevated structure’s vibration was significantlyhigher than that of the rigid foundation structure; Above20Hz, Viaduct foundation structurehave no impact on the vibration of elevated track structure.(5) Analyzing the influence of rail and elevated bridge parameters to the elevated trackvibration characteristics, including rail fastener stiffness, section, bridge, bridgebearing stiffness and damping.(6) Using ANSYS software to build the wheel system model, using modal analysismethod to analyze the vibration frequency of wheel, applied harmonic load on the wheel tread,calculation wheel radial displacement admittance value.(7) Base on the vibration characteristics of the wheel and rail, combined with noisetheoretical knowledge, carries on the forecast to the elevated track wheel-railnoise, prediction results show that: down250Hz and above2000Hz center frequency, thewheel noise plays a leading role, the peak value in3150; in250~2000Hz, rail noise isdominant. The wheel noise appeared many peak, the lowest value appeared in1000Hz, this ismainly because the wheel admittance of1000Hz is minimum.(8)Analyzing speed characteristic of wheel-rail noise, Speed respectivelyV60km/h、 V80km/h、V120km/h、V160km/h、 V200km/h, with the increase of trainspeed, the frequency of wheel-rail noise, rail noise and wheel noise all increase, and with theincrease of train speed, the rate of each frequency of wheel rail noise increases is slowingdown.(9) Effect of rail fastener stiffness, the bridge section of viaduct structure to wheel-railnoise are mainly concentrated in the low frequency, in the high-frequency range, both have noinfluence to wheel-rail noise; the bridge structure damping effect on noiseamplitude viaduct structure are mainly on the inherent frequency, having no effect onother frequency; Within a certain range of bridge bearing stiffness changes have no effect onthe wheel-rail noise.