Prestressed Containment: Behaviour when Concrete Cracking is Modelled

In containment design, the behaviour of concrete is generally modelled using elastic linear laws in calculation codes based on the finite element method. When severe accidents are considered, which generally involve beyond design basis loading, the concrete can no longer be assumed to be isotropic or have an elastic linear behaviour: cracks introduce discontinuities and non-linear phenomena. The aim of this report is to present some tools developed using the CASTEM 2000 Finite Element Code and which are used to understand the behaviour of degraded concrete structures better, when considering the conjugated effects of tendons, rebars, liner and concrete cracks. This study is aimed at establishing the feasibility and the usefulness of such an approach to predict concrete structure damaging. The results are: qualitative comparison of these theoretical results with those observed on mock-ups pressurized up to failure shows similar cracks patterns; the softening of the structure due to concrete cracking is taken into account; with temperature and pressure increase the radial vertical cracks are more numerous and their widening and depth are increasing accordingly; the stress redistribution between concrete and metallic fiber (tendons, rebars) or plate with cracks is consistent with the fundaments of reinforced concrete; the liner may be compressed even if concrete is in traction: it is caused by temperature gradient