Risk analysis of road and rail tunnels for integral design

In this paper a risk analysis procedure, which accounts both for structural reliability of the liner of road and rail tunnels and safety of passengers is presented. The idea is to consider a reliability based approach to the structural design of the tunnel liner and consequently to determine a design value of the fire load. A refined model of exodus of passengers, when considering the short time evolution of a fire scenario, characterized by the design fire source can be developed. The reliability design of the liner stems from the assumption of a target probability of failure, in case of fire accident; the design value of the fire load is determined considering a simplified model of fire propagation. Concerning exodus, on the other hand, we limit our attention to rail tunnels; thus, according with the statements of the Italian act [D.M. 24/10/2005], we do not consider very severe fire conditions and assume no coupling between safety of passengers and critical conditions of the structure.