DAMAGE MODEL FOR CONCRETE USING BOUNDING SURFACE CONCEPT

A continuum damage mechanics model for monotonic and cyclic behavior of concrete is developed. The model adopts a bounding surface concept in which the introduced bounding surface, loading surface, and initial fracture surface are chosen to be functions of the maximum accumulated damage ever experienced by the material. The initial fracture surface is the onset of fracture propagation, i.e., damage growth occurs only when the loading surface lies outside the initial fracture surface. The proposed model recognizes the different behavior of concrete in tension and compression, hence the damage due to tensile stresses is assumed to grow independently from the damage due to compressive stresses and separate compliance matrices arc introduced for tension and compression. Both hardening and softening behavior of concrete are displayed by the proposed damage-bounding surface. The model successfully predicts the essential characteristics of concrete behavior such as the nonlinearity, stiffness degradation, shear compaction dilatancy, different behavior of concrete in tension and compression, and the strain-softening behavior.