Despite a century of experience and a great deal of effort, considering the risk of thermal instability of concrete when exposed to fire is still in many cases a very difficult task as it includes many uncertainties in real practice. Moreover, there is lack of validated numerical models for predicting realistic behaviour of concrete structural elements under fire exposure. In the framework of the international benchmark Vulcain, three full scale ISO fire tests on a reinforced concrete wall, simultaneously subjected to a constant uniaxial compressive load, were conducted in CSTB in Paris, France. The duration of these tests exceeded 120 minutes. In order to assess the capability of available finite elements (FE) models to represent reinforced concrete structural behaviour under fire exposure, IRSN, within the scope of the Vulcain benchmark, developed a concrete model with help of Mazars isotropic continuum damage mechanical model ran with the CAST3M software [2]. Also, the numerical simulation of three full scale ISO fire tests of Vulcain was carried out with the help of a FE model that takes into account the values of the concrete thermomechanical parameters previously identified. The numerical model is composed of two different parts, one for heat transfer analysis and the other one for structural analysis based on a 3D FE model including concrete and reinforcing steel meshes. It is illustrated through this numerical investigation that the proposed model can predict the thermomechanical behaviour of reinforced concrete walls under fire exposure.