Safety Design-oriented Study On Fire Evacuation Behavior And Simulation In Metro Stations

With the rapid development of China’s economy,metro,with its advantages of convenience,high punctuality and high speed,has developed into the backbone of urban comprehensive transportation system.With the rapid development of metro system,emergencies occur frequently,and fire is a typical metro emergency which is easy to occur and causes great damage.It is of great practical significance to study the emergency evacuation of metro under fire.Most of the existing studies on metro safety management focus on the post-accident perspective,and less attention is paid to the important role of safety design concept in the risk prevention and control of metro emergencies.The theoretical framework of safety design proposed in this study includes two aspects: physical level and social level.The physical level refers to the safety design of the physical environment of metro stations by relevant designers and constructors in the construction design stage,and the social level refers to the safety design of emergency evacuation plans and evacuation strategies by metro operation companies in the operation stage.In addition,the existing evacuation studies homogenize all pedestrians by default.However,the composition of people in metro stations is complex,including people with large luggage,the elderly,the weak,the sick and the disabled,which need to be classified and discussed.Based on the perspective of safety design,fire evacuation in metro stations is discussed in this study.The research content mainly includes the following five aspects:(1)Establishing the theoretical basis of metro fire evacuation.The existing research on evacuation exit decision and evacuation route decision is summarized.Different research methods and application scope are summarized.Then,the micro characteristics of pedestrians such as herding behavior,cooperative behavior and panic psychology are analyzed.The mainstream pedestrian dynamics models are elaborated in detail as well.Finally,the improving angles and methods of Social Force Model(SFM)are analyzed,so as to learn the experience and find out the shortcomings of existing studies.(2)Constructing the influencing factor system of metro fire evacuation.The influencing factors are identified from physical level and social level respectively.Firstly,the physical influencing factors are analyzed through literature research from three aspects: subway station,luggage and fire-related factors.Then,the basic characteristics of passengers,evacuation behavior and evacuation psychology under emergencies are known from the social level through questionnaire survey.The social influencing factors of metro fire evacuation are identified by stepwise linear regression analysis.(3)Constructing a dynamic evacuation model of metro fire.The improved method in this study highlights two factors which are fire and psychology.In terms of fire,the spread of fire and smoke hinder pedestrians’ sight and walking speed.In terms of psychology,because of the high passenger density and dark environment,passengers are prone to panic,irritability and other psychology on occurrence of fire emergencies.However,these factors are not included in the original SFM.In this study,SFM and Fire Dynamics Model(FDM)are combined,and the factors of irritability and panic are considered.The original SFM is improved into a dynamic model that changes in real time with the changes of fire,pedestrian psychology and position.(4)Establishing fire evacuation simulation model of metro stations in large underground transportation hub.At present,there are few studies on evacuation of large-scale multi-storey underground transportation hub metro stations,which characterizes in high density of pedestrian flow and complex evacuation environment.The emergency evacuation of such metro stations needs more quantitative analysis and visual simulation research.Multi-agent-based Modelling and Simulation(MABMS)is used to simulate and analyze fire evacuation in Nanjing South Railway Station in this study.Any Logic is used to conduct comprehensive simulation modeling of this station.The improved social force model is used to define fire evolution mode and evacuation behavior rules.Simulation of the whole process of fire evacuation of Nanjing South Railway Station is conducted.Detailed analysis of evacuation time,evacuation process,blocking bottleneck area and passenger flow density of each evacuation channel are made.It can be concluded that the evacuation time is long and congestion is easy to occur at stairs,transfer passages and exits.Further analysis shows that the density distribution is not balanced,which required further safety design for emergency evacuation to improve evacuation efficiency.(5)Putting forward safety design-oriented suggestions on metro emergency safety management.Based on the physical and social levels of safety design,different evacuation scenarios are designed.Through data analysis and comparison,the evacuation result in each scenario and the influence of various factors on the evacuation process are evaluated.The integrated measures of construction and operation combined with BIM is explored as well.The results are as follows: the width of stairs has an impact on evacuation.Considering evacuation time and balance,it is more appropriate to design the width of stairs of Nanjing South Railway Station as about 3m.Besides,the wider the transfer channel,the better the evacuation performance.The narrower the passage,the more obvious the bottleneck effect.The ideal width is 14 meters.Pedestrians with large luggage should discard their luggage according to the circumstances.In several simulation experiments,the evacuation time while60% luggage is discarded is the shortest.Relevant departments are suggested to design safe areas for luggage in metro stations.In addition,the minimum number strategy is better than the nearest exit strategy.