ISSN 1000-3665 CN 11-2202/P

    考虑历史地震数据的城市轨道交通网络分型维数及韧性评估

    Fractal dimension and resilience evaluation of urban rail transit network considering historical earthquake data

    • 摘要: 为发挥历史地震数据在城市轨道交通网络(urban rail transit network,URTN)抗震韧性评估中的实际价值,须建立韧性评估与现实世界的网络拓扑特征、服务覆盖能力、客流特性、地震空间分布和土建设施易损性之间的联系,以提升韧性评估的保真度。本研究首先以上海为例,建立考虑历史地震数据的地震动计算模型以及土建设施易损性模型,然后将其嵌入URTN拓扑模型,通过控制拓扑模型中节点和连接边在地震场景下的失效状态实现两者的耦合。在韧性计算和评估方面,采用信息维数理论计算分形维数,将其作为网络韧性功能指标,使用韧性三角形计算网络韧性随时间的变化。进而应用该方法得到上海URTN的韧性评估结果地震前分形维数约为1.2,在Ms 3.0级和Ms 4.0级地震下分形维数不产生明显变化,在Ms 5.0级和Ms 6.0级地震下分形维数出现显著衰减,分别需要3400 h和5000 h的修复时间,均发生了严重的韧性损失。采取预防性加固措施后,上海URTN在Ms 5.0级地震下可维持基本正常运行状态,在Ms 6.0级地震下震后修复时间缩短约30%,韧性损失减少约34%。研究表明运用分形维数开展抗震韧性评估能考虑更多现实世界元素,可全面、定量的评估URTN在地震灾害前后的性能和韧性特征;采取预防性加固措施可以显著提高URTN的抗震韧性。

       

      Abstract: To realize the practical value of historical earthquake data in the seismic resilience assessment of urban rail transit networks (URTNs), it is necessary to establish links between resilience assessment and real-world factors, including network topological characteristics, service coverage capacity, passenger flow characteristics, the spatial distribution of earthquakes, and the vulnerability of civil infrastructure, thereby improving the fidelity of resilience assessment. Taking Shanghai as an example, this study first established a ground-motion calculation model considering historical earthquake data and a vulnerability model for civil infrastructure. These models were then embedded into the URTN topology model, and their coupling was achieved by controlling the failure states of nodes and links in the topology model under earthquake scenarios. For resilience calculation and assessment, fractal dimension was computed using information dimension theory and taken as the functional indicator of network resilience, while the resilience triangle was used to characterize the variation of network resilience over time. Subsequently, this method was applied to obtain the resilience assessment results of Shanghai URTN: Before the earthquake, the fractal dimension was approximately 1.2. Under Ms 3.0 and Ms 4.0 earthquakes, the fractal dimension showed no obvious change. Under Ms 5.0 and Ms 6.0 earthquakes, however, the fractal dimension exhibited significant attenuation, and the corresponding recovery times were 3,400 h and 5,000 h, respectively, both indicating severe resilience losses. After preventive reinforcement measures were implemented, the Shanghai URTN was able to maintain an essentially normal operational state under Ms 5.0 earthquakes. Under Ms 6.0 earthquakes, the post-earthquake recovery time was shortened by about 30%, and the resilience loss was reduced by about 34%. The results show that using fractal dimension for seismic resilience assessment can incorporate more real-world elements and comprehensively and quantitatively evaluate the performance and resilience characteristics of URTNs before and after earthquake disasters. Preventive reinforcement measures can also significantly improve the seismic resilience of URTNs.

       

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