[论文解读] Agent-based simulation of pedestrians' earthquake evacuation; application to Beirut, Lebanon

Rouba Iskandar, Kamel Allaw+9 more|arXiv (Cornell University)|Sep 6, 2023

Evacuation and Crowd Dynamics被引用 6

一句话总结

本研究开发了一种基于代理的仿真模型，用于评估黎巴嫩贝鲁特的地震疏散情况，整合了地震危害、建筑脆弱性、碎屑物以及人类行为。结果表明，可及的开放空间可将疏散失败率降低13%（从5分钟内的52%降至39%），凸显其在城市地震韧性中的关键作用。

ABSTRACT

Most seismic risk assessment methods focus on estimating the damages to the built environment and the consequent socioeconomic losses without fully taking into account the social aspect of risk. Yet, human behaviour is a key element in predicting the human impact of an earthquake, therefore, it is important to include it in quantitative risk assessment studies. In this study, an interdisciplinary approach simulating pedestrians' evacuation during earthquakes at the city scale is developed using an agent-based model. The model integrates the seismic hazard, the physical vulnerability as well as individuals' behaviours and mobility. The simulator is applied to the case of Beirut, Lebanon. Lebanon is at the heart of the Levant fault system that has generated several Mw>7 earthquakes, the latest being in 1759. It is one of the countries with the highest seismic risk in the Mediterranean region. This is due to the high seismic vulnerability of the buildings due to the absence of mandatory seismic regulation until 2012, the high level of urbanization, and the lack of adequate spatial planning and risk prevention policies. Beirut as the main residential, economic and institutional hub of Lebanon is densely populated. To accommodate the growing need for urban development, constructions have almost taken over all of the green areas of the city; squares and gardens are disappearing to give place to skyscrapers. However, open spaces are safe places to shelter, away from debris, and therefore play an essential role in earthquake evacuation. Despite the massive urbanization, there are a few open spaces but locked gates and other types of anthropogenic barriers often limit their access. To simulate this complex context, pedestrians' evacuation simulations are run in a highly realistic spatial environment implemented in GAMA [1]. Previous data concerning soil and buildings in Beirut [2, 3] are complemented by new geographic data extracted from high-resolution Pleiades satellite images. The seismic loading is defined as a peak ground acceleration of 0.3g, as stated in Lebanese seismic regulations. Building damages are estimated using an artificial neural network trained to predict the mean damage [4] based on the seismic loading as well as the soil and building vibrational properties [5]. Moreover, the quantity and the footprint of the generated debris around each building are also estimated and included in the model. We simulate how topography, buildings, debris, and access to open spaces, affect individuals' mobility. Two city configurations are implemented: 1. Open spaces are accessible without any barriers; 2. Access to some open spaces is blocked. The first simulation results show that while 52% of the population is able to arrive to an open space within 5 minutes after an earthquake, this number is reduced to 39% when one of the open spaces is locked. These results show that the presence of accessible open spaces in a city and their proximity to the residential buildings is a crucial factor for ensuring people's safety when an earthquake occurs.

研究动机与目标

• 将人类行为、建筑脆弱性和地震危害整合到贝鲁特的城市尺度疏散仿真中。
• 评估城市化和开放空间可及性受限对地震期间行人疏散的影响。
• 量化开放空间障碍对疏散效率和安全结果的影响。
• 评估碎屑物和地形在塑造地震事件中行人移动性方面的作用。
• 通过识别影响疏散成功的关键空间和政策因素，支持城市风险减缓。

提出的方法

• 在GAMA平台中实现基于代理的模型（ABM），以模拟地震疏散期间个体行人的行为。
• 模型采用黎巴嫩规范规定的峰值地面加速度0.3g来定义地震荷载。
• 利用人工神经网络估算建筑损伤，该网络基于地震荷载、土壤特性及建筑振动特性进行训练。
• 根据建筑损伤预测结果，对受损建筑周围的碎屑体积和占地面积进行建模。
• 使用高分辨率Pleiades卫星图像以增强城市环境的空间真实感。
• 模拟两种情景：一种是开放空间完全可及，另一种是因障碍物导致访问受阻。

实验结果

研究问题

• RQ1 开放空间的可及性在多大程度上影响地震发生后5分钟内成功抵达安全区域的行人比例？
• RQ2 人为障碍物（如上锁的门禁）在人口密集的城市区域中在多大程度上阻碍疏散？
• RQ3 建筑损伤和碎屑物分布如何影响行人的移动性和疏散路线？
• RQ4 地形、城市密度和开放空间可及性的综合影响如何塑造疏散结果？
• RQ5 将行为、结构和地震因素整合到单一基于代理的模型中，如何提升城市尺度疏散建模的准确性？

主要发现

• 当所有开放空间均可及时，贝鲁特52%的人口可在地震发生后5分钟内抵达开放空间。
• 当一个关键开放空间因障碍物被封锁时，相同时间框架内的疏散成功率下降至39%。
• 可及开放空间的存在是降低疏散失败率并提升人群安全性的决定性因素。
• 受损建筑产生的碎屑物显著阻碍疏散路线，并增加行人的通行时间。
• 城市化过程中绿地被移除并由高层建筑取代，会减少安全区域数量，增加疏散风险。
• 在单一基于代理的模型中整合地震危害、建筑脆弱性和人类行为，可实现对城市尺度疏散动态的真实仿真。