Numerical simulation of the load-carrying behavior of RC tunnel structures exposed to fire

A numerical model for the evaluation of the load-carrying behavior of fire exposed reinforced concrete structures is presented. It consists of a thermo-mechanical model based on a phenomenological approach. In the transient thermal and mechanical analysis the temperature dependent thermal and mechanical material properties of concrete and reinforcing steel are taken into account on the basis of test data or—if test data are not available—on the basis of the provisions of the Eurocode 2, part 1–2. For each time step the time-dependent temperature field and the structural behavior are computed in two consecutive steps. A concrete model, based on the combination of plasticity and damage theory, and an elastic–plastic model for the reinforcing steel serve as the basis for the respective material models at high temperatures. The proposed numerical model is validated by the numerical simulation of fire tests on concrete specimens and of a large scale fire test on a reinforced concrete slab. Finally, it is applied to the evaluation of the structural response of a fire exposed tunnel structure.