Study On Pedestrian Evacuation With An Improved Optimal Steps Model

With the rapid development of urbanization,the number of large public places and high-rise buildings increases quickly,and the density of people in urban area is getting higher and higher.Once emergency occurs,if people cannot evacuate timely and effectively,it is easy to cause congestion and stampede accidents,threatening people’s safety.Therefore,the evacuation process has been receiving attention from researchers all over the world.Computer simulation can simulate the process of pedestrian movement,study the characteristics of pedestrian movement,and provide theoretical guidance and technical support for the evacuation of people.At the same time,as a common"bottleneck",in urban public transportation,large public places and high-rise buildings,exits and doors play the role of connecting architectural space and thus are indispensable pedestrian facilities.However,in the event of an emergency,a bottleneck exit will affect the evacuation of high-density people and become a constraint factor restricting the efficiency of pedestrian evacuation.Therefore,this paper aims to study the evacuation simulation models,analyze the basic principles and shortcomings of the existing optimal step model,construct an improved optimal step model,and study the effect of exit characteristics on pedestrian movement at bottleneck exit in single-room scenario.Finally,providing reference for evacuation control and design at the bottleneck exit.Firstly,an improved optimal step model is established.Based on the original optimal step model,the optimization and improvement are carried out from three aspects of update rules,step length change and repulsive potentials calculation.An improved optimal model is proposed.Then,based on the improved optimal step model,the influence of different parameter changes in the model on pedestrian evacuation are analyzed.The results show that the evacuation time increases with the increase of the parameterβdescribing the step-radius relationship.With the increase of the expected maximum speedv_dmax,the evacuation time decreases sharply during pedestrian movement,but there is a critical value of 4m/s,and the evacuation time does not change significantly after the critical value is exceeded.The larger the range of variable radius[r_min,r_max],the larger the evacuation time.The linear relationship between step length and speed is more consistent with reality.As the discrete points N on the step circle increases,the evacuation time increases,but there is also a critical value.Then,model verification is completed from qualitative and quantitative perspectives（pedestrian trajectory,fundamental diagram and evacuation time）by comparing with the open source software Vadere and real experimental data.Finally,the evacuation research with different exit widths and exit positions are studied in single-room scenarios.One single exit and double exits have been investigated.The results show that the influence of exit width on evacuation has critical value under single exit and double exits.The exits located near the middle position are more conducive for the pedestrian evacuation.In the comparison between single exit and double exits,it is found when the position rather than width of a single exit changes,the evacuation time of the single exit scenario is not twice but always not less than 1.5 times of the value of the double exits scenario.For the most conducive exit location,the relationship is about 2 times.When the total width of the exit is the same,the double exits are more conducive to pedestrian evacuation than the single exit.