Numerical modelling of creep, agin and leakage of the prestressed reinforced concrete structure. Application to concrete containment building

Abstract The concrete containment building (CCB) is the third and last safety barrier to protect the environment from diffusion of radioactive products. In 2014, Électricité de France (EDF) launched the VERCORS project to improve the knowledge of leak-tightness in the CCB under air pressure loading and aging effects. VERCORS is in a 1:3 scaled CCB mock-up of a 1,300 MWe French pressurized water reactor (PWR). This paper presents a numerical methodology applied on VERCORS mock-up and numerical results focus on the gusset only, which is the lower part of the containment wall casted right after the base slab. Concrete is modeled through 3D elements while rebars and tendons are modeled by 1D elements. The simulation includes THM analysis of the gusset, prestressing phase and pressurization phase, and is conducted through a finite element code, Cast3M. The delayed strains including creep and shrinkage are especially considered. The instantaneous prestress losses, which result from friction; relaxation and pull-in at wedge, are taken into account. Regarding the long-term prestress loss due to the delayed strains, it is achieved by a kinematic relationship at interface of concrete-tendons. To describe cracks in concrete, an elastic damage model is used for the concrete elements, and the post-processing of leak-tightness is based on through crack leakage only. Those cracks appear usually at the early age phase given the restrained strains that the gusset undergoes during the hydration and hardening phase.