Exit selection and pedestrian movement in a room with two exits under fire emergency
Introduction
In the last few decades, pedestrian evacuation has become an interesting issue in the field of statistical physics. It is very important and necessary to understand the evacuation dynamics and reduce casualties and property losses when sudden accidents or disaster occurs, so far, considerable researches have been made and different evacuation models are developed by scholars in this area. Generally, these models can be classified into continuous models and discrete models. The social model developed by Helbing et al. [1], [2], [3] is the representative of the continuous models, which suggested that the motion of pedestrians can be described as if they would be subject to ‘social force’, and many observed phenomena in evacuation are reproduced by this model, such as arching, lane formation and faster is slower. In discrete models, cellular automata model [4], [5], [6], [7], [8], [9], lattice gas model [10], [11], [12], [13], [14] and network-based models [15], [16], [17], [18] are used widely. These models have high calculation efficiency and can reflect the collective behavior and self-organization phenomena [19] in pedestrian evacuation. In a word, evacuation models can simulate more and more complex human behavior, and capture microscopic and macroscopic characteristics of pedestrian flow at present.
Exit selection is one of the critical behaviors of individual during multi-exits emergency evacuation, which can affect the evacuation process and result in case of emergency. To our knowledge, some research on exit selection has been done by scholars. Based on game theory, Lo et al. [20] proposed an exit selection model for evacuation, and the choice of exits depended on how groups of evacuees interacted. Mesmer and Bloebaum [21] incorporated Bayesian game theory in exit decision model, and multiple game forms range from Bayesian games to simplified normal games were created. Based on cellular automation model, Yuan and Tan [22] and Liu et al. [23] simulated evacuation from a room with multiple exits by considering the spatial distance and occupant density factors. Alizadeh [24] found the basic parameters such as human psychology, placement of the doors, doors width, position of the obstacles, light of the environment and distribution of the crowd played an important role in the exit choice. Based on floor field model, Huang and Guo [25] used a logit-based discrete choice principle to govern the exit selection in the model. Zhao and Gao [26] considered the reserve capacity of the exit and Xu and Huang [27] introduced the direction visual field to describe pedestrian's prediction on the propagation of pedestrian flow along some directions.
Even though considerable research on exit selection and pedestrian evacuation has been done, the research considering fire emergency is still few. Due to the heavy causalities and tremendous loss of property in fire accidents, pedestrian evacuation under fire emergency should be investigated seriously. It should be noted evacuation under fire circumstance is different from that in normal situation, and the former is more complex because of the smoke and fire hazards. Studies have shown that toxic smoke, poor visibility, heat or a combination of these factors affect pedestrian movement [28], [29], [30], [31]. The physiological effects of exposure to toxic smoke and heat in fires result in varying degrees of incapacitation which may also lead to death or permanent injury [28]. Korhonen and Heliövaara [32] introduced an exit selection model under fire emergency in FDS + Evac, however, the computational efficiency was low and it costs much compute time because of the social force model used in evacuation. To consider both efficiency and accuracy, in this paper, a multi-grid model considering fire effect is proposed to simulate pedestrian evacuation and exit selection under fire emergency.
The rest of this paper is organized as follows: Section 2 introduces the model and presents the mechanism of exit selection in detail. Simulation results are shown and analyzed in Section 3. In Section 4, we close the paper by summarizing the findings and discussing our future research.
Section snippets
Model
The whole model is divided into four sub models: (1) fire simulation model [33]; (2) fire hazard model [29], [34]; (3) exit selection model; (4) pedestrian movement model. We combine the fire simulation model and fire hazard model with our exit selection model and pedestrian movement model. The interaction of these sub models is displayed in Fig. 1. Firstly, the fire data such as the temperature, visibility and CO concentration can be obtained from the fire simulation model in real time;
Simulation and results
Simulation scenario is displayed in Fig. 3. The size of the room is 20 m × 10 m inside, which is discretized into 200 × 100 cells. Two exits whose width is 1 m are located in the center of walls respectively. The number of activist, conservative and herding occupant in the simulation is Na, Nc and Nh, and the total occupant number N = Na + Nc + Nh. Every scenario is run for thirty times in the following simulation.
Conclusion
In this paper, exit selection and pedestrian movement are investigated by using a multi-grid model under fire emergency. The effect of different occupant types, the utility threshold, heat release rate, burning materials and pre-movement time on pedestrian evacuation are studied. Simulation results are summarized as follows:
- (1)
The existence of active occupants is conducive to the whole evacuation. The herding occupants only follow other pedestrians who find the exit, therefore, it becomes easy
Acknowledgments
Project supported by the National Natural Science Foundation of China (Nos. 71704168, 71704091), Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20133402110009) and the State Key Laboratory of Fire Science in University of Science and Technology of China (No. HZ2018-KF12).
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