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- 저자 : Youran Zhi (검색결과 4 건)
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Manman Chen,Jinghong Wang,Youran Zhi,Jinhua Sun 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5
The intersection of pedestrian flows is a general phenomenon in daily pedestrian traffic and emergency evacuation. However, lacking of effective controls in crowed areas will result in pedestrian deceleration, stopping, and even threats to safety in evacuation. This paper focused on exploring the influence of different intersecting angles on evacuation efficiency of pedestrian flows in high volume. Through establishing a bidirectional pedestrian flow model with different intersecting angles for a busy metro station in China based on the social force model, two factors, namely the impact between pedestrians and the conflict frequency, were firstly proposed and validated as that playing major roles in influencing the evacuation efficiency during the pedestrian intersection. With the case study, it is found that the best intersecting angle is 120 degree and angles between 40 and 80 degree are unfavorable in optimizing the average crowd speed and the crowd density. The results are verified based on the comparative analysis with some existing experimental results. The outcomes of this work can offer some guidelines to control the intersection of pedestrian flows during evacuation and can make contributions to a proposal for the related, optimized design of a structure to increasing the evacuation efficiency of a dense crowd.
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Jinghong Wang,Manman Chen,Wenyu Yan,Youran Zhi,Zhirong Wang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.1
In public gathering places, pedestrian flow congestion may happen in transportation bottlenecks. Limitations exist in the conventional judgment of congestion by considering the crowd density or the walking speed merely. In this paper, a data-driven mathematical approach based on Kernel Density Estimation (KDE) to analyze the probability of pedestrian flow congestion is proposed, which comprehensively considers the walking speed, the crowd density and the flow rate when pedestrians walk towards possible bottlenecks. With the case study of Nanjing metro station during rush hours, the advantages of non-parametric KDE compared with traditional parametric normal distribution estimation are analyzed and the optimal bandwidth for KDE is also discussed. The case study shows that the proposed method can obtain a more reliable quantitative assessment of congestion risk, as it overcomes the limitation of parametric estimation that relies on experience, and also avoids biased assessment of congestion that merely concerns single parameter of pedestrian flow. Finally, an assessment framework for dynamic congestion risk at bottlenecks is suggested. With this framework, the change of congestion situations of a monitored region can be mastered through data-driven approach, and thus the transformation of normal flowing to congestion of the crowd can be quantified through probabilistic analysis.
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Jinghong Wang,Wenyu Yan,Han Xu,Youran Zhi,Zhirong Wang,Juncheng Jiang 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.3
Emergency evacuation in subway fires is one of the hot issues in public safety. Based on Bayesian theory, a dynamic evacuation risk analysis model considering both psychological and behavioral responses of evacuees was proposed in this contribution. A subway fire scene was modeled using the Event Tree Analysis (ETA) according to the questionnaire survey at Nanjing Xinjiekou station. In this fire scenario, three control events (the fire alarm, the exhaust system and the evacuation route) were related to fire evacuation control and two control events (active escape and passive escape), which were specifically defined, were related to personnel characteristics. Subsequently, the probability of the final state of each scene was calculated by Monte Carlo simulation. Combined with the statistics of accidents and safe evacuation of subway fire cases from 1976 to 2013, the posterior probability distribution of safety evacuation was obtained after real-time dynamic updating of its precursor probability through Bayesian theory. Results show that the posterior probability of safety evacuation to succeed is around 0.8. This indicates that there is still a probability of 0.2 resulting in injury or fatalities in subway accidents even though most passengers are safely evacuated. It also suggests that utilization of 0.2 as the safety threshold would be an appropriate choice.
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Evacuation of Nursing Home Based on Massmotion: Effect of the Distribution of Dependent Elderly
Jia Li,Jinghong Wang,Bowei Jin,Yan Wang,Youran Zhi,Zhirong Wang 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.4
As dramatically increased elderly population, China is entering a society of deep aging. Due to the decline of physical functions, the elderly move slowly and have difficulty in escape. Hence, enough attention should be paid on pedestrian crowds’ evacuation in a nursing home. This paper takes Chinese old-age care institutions as the research object. Using the Massmotion based on the social force to establish the evacuation model and setting the parameters according to the movement characteristics of the elderly, this paper studied the influence of the dependent elderly on evacuation efficiency when they are distributed to the higher floors of the nursing home in different proportions. The results show that the evacuation time is significantly prolonged with the increase of the proportion of dependent elderly, and there is a controllable critical value for the proportion of dependent elderly. Aspeed-up phenomenon is observed when the old man enters the landing from the stairway, and meanwhile, with the increase of the proportion of dependent elderly, the acceleration position is gradually advanced, while the instantaneous speed declines. The results of this study can provide references in properly arranging the distribution of elderly accommodation and safe evacuation of the aged care institutions.
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