Study On Running Safety And Comprehensive Evaluation System Of High-speed Railway Bridge Under Wind And Rain Condition

With the increase of the coverage area of high-speed railway in China,the construction of high-speed railway in Northwest China has been greatly developed,and the operation mileages of the areas in harsh conditions are also increasing,so it is important to ensure the safe and efficient operation of the completed lines.According to the climate characteristics of the Lanzhou-Xinjiang high-speed railway line,this paper takes 32.6m high-speed railway simple supported beam bridge and train-set with three vehicles marshalling as research objects,and the dynamic response of train-track-bridge system under the combined action of wind and rain is studied.The influence of wind speed and rainfall intensity on the aerodynamic loads on the train and bridge is also analyzed.And based on the theory of multi-body dynamics,the variation of the train's dynamic characteristics with the changes of wind speed,rainfall intensity and train speed are analyzed,and put forward the thresholds of the train running on the bridge under the wind and rain condition.Based on this,a set of train safety threshold system suitable for Lanzhou-Xinjiang Railway is constructed.The main contents and conclusions are as follows:(1)Based on the theory of computational fluid dynamics and multiphase flow,the distribution characteristics of raindrops in the air are analyzed.And the standard k-? two equation turbulence model and Euler-Lagrange discrete phase model are selected to solve the aerodynamic loads of train and bridge under the action of wind and rain.In addition,the raindrop spectrum which obeys the M-P distribution is used to define the relationship between particle size of raindrop,number of raindrops and rainfall intensity.(2)Introduces the theory of train multi-body dynamics and the solution method of train-track-bridge coupling vibration,establishes the multi-body dynamic model of train-set by SIMPACK,and establishes the finite element model of simple supported beam bridge and ballastless track by ANSYS.Through joint simulation method with finite element-multi-body dynamics interface(FEMBS)completed the train-track-bridge coupling vibration analysis model.On this basis,the track random irregularity is simulated by using German low disturbance.In order to determine the aerodynamic loads on the train and bridge under wind and rain condition,the numerical simulation model of train and bridge are established by using ICEM CFD and FLUENT.(3)Based on the national meteorological statistical data,three meteorological base stations in Western China are randomly selected.Through the analysis of the wind speed and rainfall statistical data of the three base stations,the crosswind and rainfall conditions applicable to the climate characteristics of the Lanzhou-Xinjiang high-speed railway line are determined.It is found that under the action of crosswind,the aerodynamic load of train and bridge is proportional to the wind speed.The resistance and lift force of the intermediate vehicle are the largest.The maximum resistance and lift force are 40.4 k N and-14.04 k N respectively,but the intermediate vehicle is not affected by the yawing moment.The pitching moment of the head vehicle is the greatest but opposite to the intermediate vehicle and the tail vehicle.Under the wind and rain condition,the increase of rainfall intensity will lead to the increase of resistance and lift of train and bridge,but the influence on bridge is not obvious.With the increase of rainfall intensity,the pitching moment and the overturning moment of the three vehicles can be increased by about 40% at most.And rainfall has little effect on the yawing moment of train.Under different wind speed conditions,the influence of rainfall intensity on the train's aerodynamic load is also different.When the wind speed is low,the lateral velocity of raindrops is not high,and the rainfall has little effect on the resistance,but mainly on the lifting force of the train.When the wind speed increases to 15 m/s to 20 m/s,the lifting rate of rain to the train's aerodynamic load is the largest.The influence of rain on the train's aerodynamic load will not always increase with the increase of wind speed.When the wind speed is too high,rainfall can enhance the aerodynamic load on the train,but the impact is not obvious.(4)In the study of train running safety of high-speed railway simply supported beam bridge under wind and rain condition,due to the large stiffness of simply supported beam bridge,the change of the system aerodynamic load caused by the wind speed does not have too much influence on the bridge vibration acceleration and deflection when the train passes the bridge,but mainly affect the dynamic performance indexes of the train.Among them,vehicle lateral acceleration and wheel unloading rate are the most sensitive to environmental changes.When the wheel unloading rate is taken as the evaluation standard to determine the wind speed,rainfall intensity and driving speed limits,it is considered that when the wind speed is not more than 20m/s,the train can run at a safe speed of 300km/h.When the wind speed is not more than 24.5m/s,the running speed of the train should not exceed 250km/h.When the wind speed is no more than 26.5m/s,the train speed should be kept at 200km/h and below.When the wind speed is higher than 26.5m/s,it is suggested that the traffic should be closed in the three driving speed conditions.In addition,the rain will lead to the deterioration of the operating environment of the train.If the environmental wind speed does not change,the increase of the rain intensity will lead to the decrease of the maximum running speed of the train.This also indicates that for regions with high wind speed and rainfall,the influence of rainfall should be considered when studying the running safety of high-speed railway train.