Numerical study on concrete tunnel lining subjected to fire

In this work, a numerical model is developed to investigate concrete lining behaviour during fire, taking into account the loss of stiffness of the material subjected to high temperatures, as well as the appearance of temperature-induced internal stresses and strains in the lining. To this aim, a sequentially coupled thermo-mechanical finite element analysis is performed, by linking a heat-transfer analysis with a nonlinear structural simulation that considers concrete degradation due to fire and the interaction between tunnel lining and the surrounding ground. The effectiveness of the procedure is validated through comparisons with an analytical closed-form solution. A parametric study is also performed so as to investigate the influence exerted by different parameters, such as ground mechanical properties, tunnel depth and type of fire, on the structural response of the lining.