Research On Reasonable Location Of Wind Speed Monitoring Station On Bridge And Its Influence On Running Safety Assessment Of Trains

A bridge is one of the most important parts of railway,which plays an irreplaceable role for a train to pass through the complex terrain.To reduce the impact of complex wind environment along the bridge on the running safety of the train,the reasonable location of a wind speed monitoring station is the premise of accurate monitoring of the wind speed on the bridge.In this work,the wind tunnel tests and numerical simulations were carried out to study the influence of bridge structures,wind barriers,and canyon parameters on the wind speed distribution on the bridge.A reasonable location selection method for the wind speed monitoring stations on the bridge was proposed.The running safety of the train on the bridge in the canyon was studied based on the wind speed at the monitoring stations on the bridge.The results could improve the accuracy of the wind speed monitoring on the bridge,and would have important theoretical and practical application value for the running safety of the train.(1)The functional relationship between the characteristic parameters of the bridge structure,incoming flow speed,and wind speed at the monitoring station on the bridge were established.By extracting the characteristic parameters of the cross section of the bridge,the influence of the beam height,deck width,and windward side radian on the flow on the bridge was systematically analyzed,and the wind speed distribution profile in the vertical direction on the windward side of the bridge deck was obtained.The functional mapping relationship between the bridge structure,incoming flow speed,and wind speed at the monitoring station on the bridge was established by the piecewise fitting,the error between calculation and numerical simulation results is less than 4%.(2)The optimal locations of monitoring station on the bridge with different wind barriers were proposed.Using the wind tunnel tests and numerical simulations,the influences of the arc of the curved wind barrier(the outside of the line is negative)as well as the bending angle of the corrugated wind barrier and the straight slope ratio(the length of the vertical side to the length of the inclined plane)on the flow and the wind speed at the monitoring station on the bridge were studied,and the corresponding relationship between the optimal location of the wind speed monitoring station on the bridge and the parameters of the wind barrier was obtained.For the curved plate radian within the range of-10° ～ +5°,the optimal extension length of the monitoring station was 0 ～ 0.64 m.When the bending angle of the corrugated wind barrier increased from 0°to 90°,the optimal extension length of the monitoring station would be0.62 ～ 1.3 m.When the ratio of straightness to inclination increased from0.41 to 2.12,the optimal extension length would be 0.82 ～1.1 m.(3)The influence mechanism of the canyon on the wind speed distribution in the canyon was proved,and the influence laws of the length,bottom spacing,and slope of the canyon on the wind speed distribution on the bridge were obtained.Based on the distribution of the flow in the canyon,a simplified simulation method of the equivalent height and contour was proposed,which could significantly reduce the cost of the numerical calculation.Based on the machine learning,the location selection of the wind speed monitoring station on the bridge in the canyon and the wind speed prediction model were established.According to the characteristic parameters of the canyon and bridge,the optimal layout interval of the monitoring station on the bridge and the corresponding wind speed were determined.(4)The running safety of the train based on the wind speed at the monitoring station on the bridge in the canyon was evaluated.Based on the distribution of the flow in the canyon and the wind speed at the monitoring station,the difference of the aerodynamic loads and its mechanism on the bridge with different heights were analyzed.A simplified calculation based on the maximum wind speed was proposed,where the running safety of the train on bridges with different heights in the turbulent layer could be evaluated,similar to that in the stable layer,using the wind speed at the monitoring station on the bridge at the specific height.The applicability to the assessment of the train running safety in the turbulent layer was improved,and the difference of the maximum characteristic wind speed between the simplified and original calculation was only 5.86%.