In certain accidental situations, it is important to assess the consequences of severe thermal loading on the mechanical behaviour of concrete structures, particularly with regard to potential cracking. This is particularly the case in the study of corium-concrete interaction. As part of the assessment of the consequences of a hypothetical severe accident, a core meltdown may be considered. The molten mixture, known as corium, then spreads into the reactor and comes into contact with the concrete. Various phenomena can occur, leading to partial ablation of the material. Given the stakes involved in terms of environmental protection, it is essential to have modelling tools that can represent the mechanisms involved. The aim of this thesis is to develop a comprehensive simulation methodology to represent the mechanical consequences of corium-concrete interaction, including local-scale modelling to represent the ablation of the cementitious material. Particular attention will be paid to the concrete cracking model (development of a model adapted to severe thermal loading, concrete ablation criteria) and to the thermal-mechanical-flow chaining of tools for representing the penetration of corium into cracks. This work will be carried out in collaboration between CEA SACLAY (which has the first tools for simulating thermomechanical behaviour) and CEA Cadarache (which has numerical and experimental expertise in corium-concrete interaction).