Modelling of thermo-mechanical behaviour of tunnels under fire conditions

Major fire events in tunnels have shown severe consequences in their structural performance, as reported in several incidents in the last decades. Particularly, due to the enclos-ure geometry of tunnels, intense thermal loading may develop in comparison to typical fires in buildings, which may result in more damage. Even though tunnel linings are an important com-ponent in transportation infrastructure, the understanding of their behaviour under high tem-peratures is limited. This paper aims to study the thermo-mechanical response of tunnels subjected to fire using nonlinear finite element analysis (NLFEA). For this purpose, recent experimental tests of large-scale reinforced concrete tunnels with and without fire protection are simulated. Different modelling approaches and strategies are discussed, and a detailed descrip-tion of the constitutive model employed is presented. The results obtained in the simulations indicated that the numerical analysis can be used to investigate the thermo-mechanical behav-iour of concrete structures.