Simulation Analysis Of Traffic Risk In The Bridge-tunnel Connection Section Of Expressway In Mountainous Region Under Crosswind Action

Due to the limitation of complex terrain in mountainous areas,the expressway in mountainous areas is mostly constructed in the form of combining bridges with tunnels.However,the weather in mountainous areas is changeable,and the bridge and tunnel sections are often affected by bad weather such as crosswind,which easily leads to traffic accidents.The crosswind will affect the driving stability of the vehicle when the vehicle runs normally at the bridge-tunnel connecting section of mountain expressway.Crosswind accounts for 0.02% of the total accidents as a factor causing traffic accidents,but it will cause serious casualties and huge property losses once it happens.And at the same time,it will also affect the traffic state of the accident site.Therefore,in order to effectively reduce the incidence of traffic accidents in mountain expressways,the influence of crosswind on the traffic safety of vehicles in the bridge-tunnel connecting section of mountain expressways needs urgent research.In order to explore the influence of crosswind on driving safety in the connecting section of bridge and tunnel of mountainous expressway,based on the basic theory of vehicle aerodynamics,this paper uses Carsim8.02 vehicle dynamics simulation software to analyze the combined changes of different wind speed,wind direction,vehicle type,vehicle speed and road friction coefficient,and selects the critical danger limit value as the driving safety evaluation index to evaluate the driving safety of vehicles under various working conditions.The research ideas,methods and main research results of this paper are as follows:1)By analyzing the field measured data of wind(the monitoring data of the third branch section of Inner Mongolia Road and Bridge Jingwu Expressway Project in Inner Mongolia from August 28,2020 to August 30,2020 and the monitoring data of Chifeng area in China Meteorological Data Network from January,2017 to December,2020),the change law of wind in daily cycle and annual cycle was explored,and it was found that the wind direction statistics during the observation period showed that the dominant wind direction at each observation point of the average wind field was obvious.The northwest wind and the southeast wind are dominant(WNW,S-SSE),and the gale period in Chifeng area is mainly concentrated in spring and autumn,and the maximum wind speed in every month from 2017 to 2020 exceeds Grade6(10.8m/s),and the daily maximum wind speed in a year is normally distributed.2)A field calibration method of vehicle dynamics simulation software is proposed,which mainly includes the design of calibration method,the selection of field calibration site and the introduction of equipment,the collection and processing of field data,the establishment and output of simulation software model and the comparison of field test and simulation results.At the same time,the commonly used vehicle dynamics simulation software is summarized,Carsim8.02 is selected as the verification simulation software,MD and RMSE are used as evaluation indexes,and the field and simulation test output data are compared and analyzed.The data show that Carsim field and simulation test data have a good overall fitting degree.3)Based on Carsim8.02 vehicle dynamics simulation software,the crosswind model,vehicle model and road model based on various factors are established,including setting different wind direction angles,wind levels,different vehicle types,vehicle speeds and different road condition levels.The limit value of cornering danger is put forward as the evaluation index of driving safety,and the calculation formula of the limit value of cornering danger is established based on the driving track of the vehicle,and an example is given.At the same time,the combination forms of simulation conditions are listed,and the safe distance and safe reaction time of side deviation are used as output indexes,and the corresponding calculation formulas are established and an example is given.4)From the point of view of road design,combined with the results of lateral safety distance simulated by Carsim8.02,the influences of wind direction angle,wind level,vehicle type,vehicle speed and road condition grade on lateral safety distance are analyzed,and regression analysis is carried out on the results of various working conditions,and the driving safety distance models of cars and SUVs under crosswind are established respectively,which can give effective suggestions on the length design of straight bridge-tunnel connection section under crosswind in road design,and provide a basis for road design research under crosswind5)From the point of view of vehicle control,combined with the safety response time results simulated by Carsim8.02,the influence of wind direction angle,wind level,vehicle type,vehicle speed and road condition grade on safety response time is analyzed,and linear regression analysis is carried out on the results of various working conditions,and the driving safety response time models of cars and SUVs under crosswind are established respectively,which provides a basis for the research and development of vehicle control systems in the future.In order to analyze the driving risk of vehicles in the bridge-tunnel connecting section of mountain expressway under crosswind,this paper puts forward the field test verification method of dynamic simulation software,establishes simulation model by Carsim8.02,studies the influence of vehicle model,vehicle speed,road and wind speed on vehicle safety response time and safety response distance,and puts forward the model of vehicle safety response time and safety response distance,which provides a basis for the analysis and research of vehicle safety,road design,vehicle control and unmanned driving under crosswind in the future.