The Coupliing Vibration Characteristics Of Steel Struss Girder Suspension Bridge-Train Based On Wind Field Measurement In Mountainous Area

In recent years,railway engineering has been developed rapidly because of its safety characteristics.When trains run on bridge girder,the complex driving wind environment may make the train driving safety,passenger comfort and other problems prominent.The outstanding characteistics that uneven distribution characteristics of wind along the bridge span in mountain valley,aerodynamic parameters of the railway steel truss girder and railway vehicles,make the previous wind-vehicle-bridge coupling analysis method is not fully applicable.This may affect the coupled vibration response of the railway vehicles and the bridge girder.By wind tunnel test and field measurement method,a series of studies are to be carried out.An introduction is made to the wind characteristics in a mountain valley.And,its research methods and ideas are pointed out.Wind characteristics along the long-span steel truss railway suspension bridge in mountainous is investigated by the radar laser anemometer,including the mean wind speed distribution,wind direction distribution,turbulent intensity,turbulence integral scale,wind velocity spectrum and spatial correlation characteristics.Wind characteristics from wind tunnel tests is compared with that in field measurement.The results show that mean wind speed around the middle-span of the bridge is relatively the largest and is gradually decreased at both sides of the valley,which shows a sinusoidal function law.A mean wind speed distribution function is proposed.While,the mean wind speed distribution along the bridge in wind tunnel tests is relatively uniform,that is,the gap between the mean wind speed values at different monitoring points along the bridge is small.The ratio of transverse,vertical and longitudinal turbulent intensity is increased along the bridge.Turbulent integral scales vary relatively large along the bridge and the largest turbulent integral scale across the mid-span of the bridge.With the increase of distance spaces,correlation coefficients of wind speeds are gradually decreased,and the correlation characteristics is worse.Roughly,the correlation characteristics of longitudinal wind speeds is significantly better than that of transverse and vertical wind speeds.The correlation characteristics transverse and vertical wind speeds is roughly the same.Based on the sectional model wind tunnel test,turbulent wind field in wind tunnel is conducted and the spatial distribution characteristics of buffeting forces on bridge girder and railway vehicles are studied.The coherence functions and three-dimensional aerodynamic admittance functions are also obtained.The results show that when the reduction frequency is less than 0.8,the cross correlation of buffeting forces on the main beam is better than that of the wind speed,which are roughly the same with the wind speed in condition the reduced frequencies are larger than 0.8.When the reduced frequency is lower than 1,the Sears function is significantly larger than the aerodynamic admittance function of the steel truss girder section.When the reduced frequency is larger than 1,the aerodynamic admittance function of the steel truss main beam is close to the Sears function and smaller than the Sears function.The crosscorrelation characteristics of buffeting lift force on train vehicle is better than that of the lateral force,and the correlation of moment is relatively weak.When the reduction frequency is less than 0.1,the aerodynamic admittance values of the lateral force and lift force keeps change small and the value is smaller than 1,and the aerodynamic admittance values of the lift force is less than that of the lateral force guide value.When the reduction frequency is larger than0.1,the aerodynamic admittance values of the lateral force are gradually decreased with the reduction frequency increased.The wind-vehicle-bridge system coupling vibration analysis method at mountain valley is summarized.The influence of key aerodynamic parameters,such as wind field and buffeting force,on responses of bridge and railway vehicles is clarified.When the wind field is adopted by the field measurement results and the aerodynamic admittance functions are adopted by wind tunnel tests,the lateral displacement of the girder is reduced by 44.8% than that when wind spectrum is the specification recommended values and aerodynamic admittance functions are ignored.While,the maximum absolute value of the wheel load reduction rate is decreased by 41.9%.The absolute value of the mean transverse force of the train wheel axis is decreased by about 45.7%.The lateral displacement of bridge girder,maximum absolute lateral acceleration and mean variance under the specification recommended wind spectrum are larger than that under the wind field measurement results.The mean variance of the lateral acceleration is reduced when the wind field is adopted by field measurement rather than wind tunnel tests.