The prescriptive design guidelines are an essential basis when assessing a required nominal fire resistance. However, a prescriptive approach cannot be used to assess the fire performance of reinforced concrete (RC) structures during the cooling phase of natural fire scenarios. IRSN conducted a numerical study with the intention of modelling RC structures exposed to natural fire. For this purpose, an adapted finite element model was developed, using CAST3M finite element code (Verpeaux et al., 1988). The behaviour of concrete material was simulated using the Mazars elastic isotropic damage model (Mazars, 1984), while a user-defined procedure was used to calculate the concrete properties taking into account the full temperature history of the analysed structure. The effect of transient creep strain according to the model of Anderberg and Thelandersson (1976) was explicitly considered. In order to validate the implemented model, the transient tests conducted by Anderberg and Thelandersson (1976) and the experiments conducted by Maclean (2018) have been simulated considering siliceous and calcareous concrete specimens according to EN 1992-1-2 (2004). The studies presented in this paper demonstrate the adequacy of the implemented mechanical model, taking into account the transient creep strain and realistic concrete properties, for describing the behaviour of concrete structures exposed to natural fire considering the fire decay phase.