How can a Crack Opening be Extracted from a Continuous Damage Finite Element Computation? Application for the Estimation of Permeability

International audienceThe assessment of the diffuse damage and the crack opening are key parameters for estimating the integrity and the strength of concrete structures in the face of environmental attacks ruled by diffusion and/or Darcy's transfers. Continuum enhanced approaches to concrete fracture are able to represent diffuse damage, crack initiation and propagation. They regard damage process as an ultimate consequence of a gradual loss of material integrity. These models, however, do not predict the crack opening. Therefore, we propose to compute the crack opening using cinematic equivalence at failure between a continuous and a discontinuous description. For this purpose, we consider a discontinuous displacement field with a given jump from which we compute the equivalent non‐local strain. From a classical finite element computation we obtain a distribution of the non‐local strain provided by an integral or gradient damage model. The displacement jump is computed assuming that both non‐local strains are equal at the location of a crack. Finally, using this displacement jump, permeability of a cracked concrete may be determined with Poiseuille's law. This approach will be validated against experimental results on loaded discs in Brazilian splitting test