Quantitative fire risk assessment of road tunnels through advanced consequence analysis

The thesis is focused on the fire risk in road tunnels and its numerical estimation through quantitative risk analysis (QRA) supported by fire and evacuation modeling. According to the in-force regulations concerning the Trans-European Road Network, the quantitative risk assessment is a mandatory step for existing tunnels that do not comply with the minimum structural safety requirements. When the risk does not reach the acceptability threshold, alternative configurations and mitigation strategies must be designed to reduce the residual risk under a suitable level, and again the QRA is useful to evaluate which choice is the best considering the actual risk reduction, in terms of Expected Value (EV) per year and cost-benefit ratio. The thesis is divided in three macro-sections, which are intended to provide, on the one hand, an overall view of the complexity of road tunnel systems and, on the other hand, the possibility of a precise estimation of the consequences of a fire event through advanced modeling, in line with the state of the art of the fire safety engineering (FSE). The first section introduces the reader to the topic of fire risk in road tunnels by the characterization of their main features (traffic, systems, etc.), the statistics and the regulations which impose the QRA. In the second section, a detailed description of background aspects of tunnel fire safety is conducted; in addition, parametric studies aimed to assess the capabilities of models in a tunnel context are illustrated. The third section details the proposed methodology for QRA, which is finally applied to two cases studies of unidirectional and bidirectional tunnels.