Structural safety assessment of concrete tunnel lining subjected to fire

The basis of a possible fire design and verification approach to the linings of RC tunnels, using the performance-based approach, is presented. Starting from an extensive literature review, a selection of the most relevant tunnel fires was analysed. The study of structural consequences of these real fires may be considered as experimental data of tunnel in fire, to define the possible fire damage levels. Back analyses were carried out to define the main parameters controlling each damage state, whose temperature range is determined via fluid-dynamic analyses based both on fire zone models and Computational Fluid Dynamic Modelling. Therefore, the novelty of this paper is that the proposed methodology introduces the structural damage levels for the tunnel lining in fire, according to a performance-based approach. In the second part of the paper, the proposed approach was applied to a real concrete tunnel to assess its potential fire damage level. First of all, the expected damage level of the underground structure was identified through the gas temperatures reached during different real fire scenarios, where no fire damage was observed. This result was confirmed by analysing both the temperatures and the stresses of the structural lining, through advanced thermo-mechanical analyses.