• temperature distribution
• structural behaviour
• heat release rate
• fire
• concrete
• tunnel

A comparison between the results obtained from a Computational Fluid Dynamic (CFD) simulation and from the application of an empirical formula for determining the temperature distribution inside a tunnel in case of fire is presented. The temperature is measured and calculated at different distances from the location of the fire and at different time intervals. The fire considered varies with time following a time-heat release rate curve which has a parabolic growing phase, a constant period and a linear decay. The comparison reveals differences in the results. The temperatures calculated with the empirical formula resulted higher than the temperatures obtained by means of the CFD simulation. Two finite elements analyses of a tunnel structure subject to fire were carried out applying respectively the temperature curve obtained from the empirical formula and the ISO834 curve. The definition of a limit state function based on the punctual strain status was used to assess the structural behaviour of the tunnel and compare the results from the two finite element analyses.