Assessing and enhancing the fire resilience of urban road tunnels: A New framework and case study

Fire is one of the most common hazards in urban road tunnels. However, due to a lack of a systematic understanding of the full evolution of tunnel fires, existing studies often struggle to accurately capture the multifaceted impacts of such events. In this paper, a comprehensive resilience analysis framework for urban road tunnels subjected to fire accidents is proposed, grounded in the concept of resilience and the distinctive characteristics of tunnel fires. This framework innovatively integrates three key indices, namely, frequency index, casualty index, and traffic index, to provide a holistic assessment of tunnel fire resilience, and the corresponding quantification methods of these three indices are discussed in detail. Subsequently, the framework is applied to a cross-river tunnel in Shanghai as a case study to demonstrate its implementation. Finally, the effectiveness of five measures aimed at enhancing fire resilience is evaluated based on a representative scenario. The results indicate that the tunnel's frequency index is 4.92. Under the most adverse fire scenario, both casualty and traffic disruptions are significant, with a casualty index of 39.88 and a traffic index of 0.576. Moreover, among the resilience enhancement measures, improving ventilation conditions proves to be the most effective in mitigating casualties, while for the traffic index, implementing traffic management is more effective than improving the efficiency of emergency services. These findings provide valuable insights for fire prevention design of tunnels and offer practical guidance for the decision-making of operational management departments.