A framework of elastic-plastic damaging model for concrete under multiaxial stress states

The paper concerns the description and the validation of a constitutive model for concrete characterized by a combined plastic-hardening-damage-fracture dissipative criterion developed within the framework of the simple material model, so that its numerical implementation is easy and robust. Two different damage isotropic mechanisms associated with tensile and compressive strain processes are introduced and two hardening variables are used; the first rules the plastic hardening while the second controls the compaction of the material. The limit domain is defined through the envelope of three yield criteria presenting a strong and original coupling between plastic and damage dissipative mechanisms. It is demonstrated that the proposed framework allows the reproduction of some distinctive features of the behavior of concrete under multiaxial stress states, such as volumetric hardening in triaxial compression load processes, the increment of strength under confined compression, post-peak dilatancy, varying degradation of the elastic stiffness in tensile or compressive stress states, the increase of the limit strain in cyclic processes. A comparison of the numerical predictions with the literature experimental tests is presented. The limits of the proposed model are also discussed in the paper.