The coupling of non-linear effects of temperature and initial load ratio on relaxation is considered. • The model for relaxation of prestressing bars at high-temperature (20-140°C) is developed. • The model is validated for relaxation test with a stepwise heating (20°C-100°C-140°C).

This article presents the application of a thermo-hydro-chemo-mechanical (THCM) model to a real complex structure of reactor confinement (mock-up VERCORS from EDF) by taking into account the specificities of the construction (construction consequences), the distributed reinforcements and the material heterogeneity of massive structure. The experimental campaigns were conducted during and after the construction of VERCORS. The early-age behavior of concrete is first modelled based on a multiphasic hydration model to ensure the thermal evolution. Then a 3D mechanical model is used to predict the consequences of hydration, temperature and water variations on mechanical behavior. An alternative approach to consider the structural effect of distributed reinforcement without explicit meshing of reinforcements is implemented and is able to reproduce the influence of reinforcement on the crack patterns. Moreover, the “Weakest link localization” method is also adapted to deal with a probabilistic scale effect due to the material heterogeneity of massive structure. It permits to assess directly the most likely tensile strength which can treat the first crack in softening part of the loaded volume of structures.