Elastoplastic Model with Damage for Reinforced Concrete

During the loading process, stress and strain are inhomogeneous in the reinforced concrete, so it is difficult to determine the constitutive relation from the tests. In order to ignore the difficulties in identifying the influence of such nonhomogeneities, an elastoplastic model with damage for reinforced concrete is proposed by the observed load-deformation relations in this paper. It is assumed that behaviour of reinforced concrete element is decomposed in two parts. In the first part, which refers to the damaged part, the behaviour is depicted as rigid, perfectly plastic with zero yield strength. The second part, representing topical behaviour, is non-softening and obeys an elastoplastic constitutive law. During the loading process, topical behaviour is “transformed” to damaged one. The model is divided into four intervals: the elastic stage, the based elastoplastic stage on concrete, the based elastoplastic stage on reinforcement and the strain softening stage. The damage variable is responsible for the softening in strength, for the degradation of the elastic shear modulus, and for induced anisotropy. The parameters of rebar and concrete are calibrated by the softened truss mod proposed by Abdeldjelil & Hsu and the modified compression field theory proposed by Vecchio & Collins, considering the interaction between the concrete and reinforcement. The model is applied to analyze the load-deflection relationships of RC beams and shows very good agreement with the experimental results.