Study On Train Running Performance Of Super-Span Rail-cum-Road Suspension Bridge Under Strong Wind Loads

Suspension bridge with light weight and strong spanning ability is a practical choice when high-speed railway needs to cross wide river and canyon.Meanwhile,if the highway and railway are consistent,the superspan rail-cum-road suspension bridge is a sort of more economical scheme.However,the long-span suspension bridge has relative low stiffness and complex wind environment,so the bridge and train are vulnerable to strong wind effects.If we want to ensure that the train can safely and steadily passing bridge,we need to study the train running performance under strong wind loads.The suspension bridge scheme of the main span 1120m Libu Yangtze River Rail-cum-Road Bridge on JingJing high-speed railway was taken as the research object in this thesis.The main research contents and conclusions of this thesis are as follows.(1)According to the principle of total potential energy with stationary value in elastic system dynamics and the“set-in-right-position" rule for assembling system matrices,the wind-train-bridge space coupling vibration model and the finite element model of bridge were established in this thesis.On this basis,the natural vibration characteristics of the bridge were analyzed in this thesis.The results show that the bridge has close natural frequency interval and relatively low natural frequency.(2)Considering the influence of vehicle load and the additional deformation of temperature rise and creep,the simulation calculation of train-bridge spatial coupling vibration under windless condition was carried out in this thesis.The results show that the bridge stiffness meets the requirements and it has good train running performance under windless conditions.(3)The computational fluid dynamics simulation software was used to analyze the flow field characteristics of main girder and train-bridge combination in this thesis.At the same time,the correctness of the model was verified by wind tunnel test data.The analysis results of velocity field and pressure field show that inclined bar,vertical bar and deck accessory structure of bridge make more vortex inside truss.And the flow field is more complex,resulting in uneven distribution of train wind pressure.(4)Without wind barrier and considering vehicle load and additional deformation,the simulation calculation of wind-train-bridge spatial coupling vibration was carried out in this thesis.The purpose was to study the influence of different wind speed,wind attack angle and train speed on the train running performance,and to obtain the train speed-wind attack angle-wind speed threshold of the bridge.The calculation results show that 0° attack angle is not the most unfavorable attack angle of the bridge.When the average wind speed of the bridge deck is not higher than 20m/s,the train can pass at the design speed of 250km/h.Train speed should be limited to 175km/h when wind speed reaches 25m/s.When the wind speed reaches 30m/s,the bridge should be closed.(5)The influence of the height and position of the wind barrier on the train running performance of the bridge was studied in this thesis.The calculation results show that the wind barrier effectively guarantees and improves the safety of train operation.This effect will be more obvious with the increase of wind barrier height.And the highway lateral setting scheme is better than the railway lateral scheme.