| With the fast economic growth,accelerated urbanization and enhanced infrastructure construction,the number of buildings is increasing and the structure is becoming more complex,the corresponding capacity of these buildings are also increasing,resulting in higher than ever urban population density.Once an emergency occurs,if the evacuation process cannot be carried out effectively,congestion and even stampede accidents may be triggered.In the process of evacuation,exit is usually the "bottleneck" and the exit selection behavior of pedestrians has an important impact on evacuation efficiency.Therefore,studying exit selection behavior in the process of evacuation has an important role in ensuring pedestrian safety in emergencies.To solve the problem of exit selection in the process of evacuation,we firstly analyze the influence factors of exit selection.These factors can be divided into dynamic factors and static factors.Dynamic factor refers to the that changes with time in the simulation process,including e.g.,the walkable space before the exit,real-time flow rate and distance at the exit.Static factor refers to the quantity that does not change with time,e.g.,exit width and layout.The dynamic factors are introduced into the model by combining the entropy calculation method in information theory and finally we establish the evacuation exit selection model based on dynamic entropy field.With the entropy value in dynamic entropy field,the dynamic adjustment process of exit selection in evacuation process can be reproduced.Finally,we analyze the influences of dynamic factors and static factors on exit selection and evacuation efficiency.The results show that,(1)In the model,the radius of the perceived area and the reserved capacity difference of the exit jointly determines the walking space before the exit,and the entropy represents the effect of the real-time flow and distance of the exit,thus affecting the interaction among pedestrian crowds.Compared with the evacuation model without considering entropy value,the proposed model can effectively reduce the possibility of pedestrian exit choice changing.The walkable space before exit has an impact on exit selection and evacuation efficiency.Setting a reasonable difference between the radius of the sensing area and the reserved capacity,the use of the two exits will be balanced and thus improving the evacuation efficiency.Under the same condition,the larger the sensing area,the more balanced use of the two exits,and the higher the evacuation efficiency.(2)Exit width,exit spacing and exit location all affect evacuation efficiency.When the other conditions are the same,the evacuation efficiency gradually increase with the increase of the exit width,and finally tends to be stable.The exit spacing also affects the evacuation efficiency,when the value is too large or too small,the evacuation efficiency will be low,there is a critical value to make the evacuation efficient.In addition,the location of exits also affects the evacuation effect,in the dual-exit evacuation scene with no internal obstacles and two exits set in parallel,when both exits are in the center of the wall,the evacuation efficiency is the highest.In complex evacuation scenarios with internally exit,when the two external exits are distributed on the same wall and the exit layout of the internal exit are located in the center of the internal wall,pedestrian crowd can evacuate efficiently.When the two external exits are parallelly distributed on different walls,the evacuation efficiency is still the highest when the internal exit is in the center of the internal wall.When the internal exit is in the center of the internal wall,the two external exits located on the same side of the wall are most beneficial to evacuation.When the internal exit is in the non-central position of the internal wall and the external two exits are located on the same side of the wall and meanwhile away from the internal exit,the evacuation will be efficiently. |
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