Coupling Vibration Of Vehicle-Bridge System Under Wind Environment For Suspended Monorail Transit

As a new-type of urban monorial transit system,suspended monorail transit has a great application prospect in China with the advantages of climbing ability and small turning radius.The suspended monorail vehicle travels under the track beam which the bottom side is opening,the mode of operation,guide principle and wheel-rail relationship are totally different from traditional railway vehicle-track-bridge system.Also,due to the small cruve radius of suspended monorail line and the complex topographical condition,the issues of wind-induced vibration of bridges and the running performances of vehicles in crosswind environment are proved to be the critical and difficult points.Therefore,the following studies are carried out to investigate the driving performance of suspended monoral vehicle for different type lines in crosswind condition.Main study works are as follows:(1)Based on the multi-body dynamic method and the structural features of suspended monorail vehicle,the cornering characteristics of the rubber tires and the guidance force of guide wheel are fully considered,a dynamic model of suspended monorail vehicle with 34degrees-of-freedom is established.According to the compression deformation and contact model of walking wheel and guide wheel,the geometric and mechanical coupling relationships between vehicle and bridge are studied and the dynamic equations of suspended monorail vehicle-bridge interaction are derived.Also,referring to the power spectrum of road surface roughness and American railway sixth grade track irregularity,the track ireegularity of suspended monorail line is investigated.Furthermore,the vehicle-(double lines)bridge coupling system is established using the rigid-flexible coupling method,the effects of vehicle speed,tire stiffness and train formation on the running performance of vehicles and dynamic responses of bridges are evaluated.(2)A three-dimensional wind-vehicle-bridge(WVB)coupled vibration model is established for the suspended monorail system.Spectral representation method is adopted here for the simulation of stochastic wind velocity field,according to the comparison of the simulation results and objective results of wind spectrums and coherence functions,the reliability of the simulation fluctuating wind filed is verified.The wind velocity time samples effected on the bridge and moving train are obtained,then the computational fluid dynamics(CFD)method is adopted to analyze the aerodynamic coefficients.Finally,the staitic wind force and buffeting forces loaded on the bridge and moving vehicle are simulated respectively.(3)Based on the computational fluid dynamics(CFD)method,the change of aerodynamic characteristics of vehicle and bridge during the meeting of two trains for suspended monorail system in crosswind condition is studied,the phenomenon of the sudden change of wind load effected on the vehicle is explained.To verify the accuracy of the numerical analysis of CFD method,the aerodynamic coefficients of the vehicle and bridge when two trains meet each other are obtained by the wind tunnel test,which are consistent with the results calculated using CFD method.To focus on the issues of the running safety and comfort of vehicles when two suspended monorail trains pass each other under crosswind,some conclusions are drawn:There exists the phenomenon of sudden change of wind load at the beginning and the end of the meeting of the two trains,which is the control factor effected on the lateral responses of the leeward vehicle;the lateral responses of suspended monorail vehicle are sensitive to the fluctuating wind;the mean wind speed has a great negative contribution to the acceleration responses of leeward vehicle and the effects on the vertical displacements of bridge is limited.(4)As for the driving performance of suspended monorail vehicle passing through the curved bridge under wind environment,the critical parameters of curve line are designed,such as the transition curve length and superelevation,and a curved bridge model is established using the finite element method.According to transformable relationship between the local coordinate system and the global coordinate system,the vehicle-curved bridge coupling vibration system is established,the impact factors,such as the superelevation,vehicle speed,pre-guidance force and curve radius,on the dynamic responses of suspended monorail vehicle passing through the curved bridge are investigated.Results show that the direction of the yawing moment of the front bogie is in accordance with the turning direction of vehicle,while the yawing moment of the rear bogie is in opposite direction;the superelevation has no influence on the vehicle gauge;vehicle speed is a key factor to the running safety of suspended monorail vehicle;the value of pre-guidance force should be set reasonably;the curve negotiation ability of vehicle is higher with the increase of curve radius.(5)According to the small curvature radius bridge,the angle between wind and vehicle changes when vehicles pass through the curved bridge.To investigate the difficult and intractable issues,the vibration analysis of wind-vehicle-curved bridge system is investigated based on the decomposition approach,the influences of wind direction,superelevation,vehicle speed and fluctuating wind on the dynamic response of bridge and vehicle are analyzed.