SIMPLIFIED MODEL OF UNILATERAL DAMAGE FOR RC FRAMES

This paper describes an approach, based on the concepts of continuum damage mechanics and standard inelastic analysis of reinforced concrete (RC) frames, to the modeling of the hysteretic behavior of RC frames. A frame member is considered as the assemblage of an elastic beam-column and two inelastic hinges, as in the conventional lumped plasticity models. Three sets of internal variables, which measure plastic rotations and the state of damage of the member, are introduced. An expression for the flexibility matrices and the complementary strain energy of a member are proposed as a function of these internal variables. The resulting model can be classified as ''unilateral,'' i.e., it is assumed that damage due to positive actions has no influence in the behavior under negative action due to the closure of cracks when moments change sign. The accuracy of the model is verified by simulating various experiments for which data were available in the literature. The model is very simple in nature and as a result is not comprehensive; however, the approach presented is amenable of further generalizations.