As the past has already shown, re incidents happened several times in tunnels, for example in the Mont-Blanc Tunnel in 1999. To investigate or to predict the eect of such serious thermal loads on a reinforced concrete tunnel sections suitable simulation models are required. This master thesis shows the numerical investigation of underground structures made of reinforced concrete subjected to re loading. Three dierent types of tunnel cross-sections under a three hours re load were simulated: a rectangular cross-section, a arched cross section and a circular cross-section. The simulation of the circular cross-section includes four dierent static systems. In order to perform a realistic simulation, an asymmetric mechanical load was considered. To perform a comparison between the dierent structures, the main attention was paid to the internal forces (bending moments, axial forces) and deformations. The numerical investigations comprise three dierent model assumptions. The used model assumptions are: linear-elastic material behaviour considering an equivalent temperature distribution; non-linear, elasto-plastic material behaviour considering an equivalent temperature distribution; non-linear, elasto-plastic material behaviour considering a non-linear temperature distribution Furthermore, the material parameters and their temperature-dependent evolution were taken from two dierent policies (ÖNORM EN 1992-1-2  and CEB ). The results showed that the stiness of the cross sections was signicantly reduced by using non-linear material behaviour (i.e., limitation of stresses by the respective temperature-dependent strength). In this way, the internal forces (bending moments, axial forces) decreased and the deformations increased signicantly compared to the linear simulation without the limitation of stresses. In order to carry out an economic design of underground structures also for the bad case "fire", such realistic non-linear simulations are essential.