A.A.Khosroshahi - Ph.D Candidate Department of Civil Engineering, K.N.Toosi University of Technology, Tehran, Iran
S.A.Sadrnejad - Professor Department of Civil Engineering, K.N.Toosi University of Technology, Tehran, Iran

This paper proposes a framework for simulating behavior of concrete under multiaxial loadings on any stress path including cyclic loading and postpeak behavior based on the semi-micromechanical aspects of plasticity and using substructure model that can be used in the plasticity and fracture analysis of concrete and reinforced concrete structures. With using sub-loading surface aspect the kinematics and isotropic hardening are applied in the model making it capable of simulating the behavior under any stress path such as cyclic loading in the ascending/descending branch of loadings. Multilaminate based model is used to provide a relation between stress/strain and yield function on planes of various orientation. Four basic stress states including compression-shear with increase/decrease in the compression/shear rate, tension-shear and pure compression are defined and the constitutive law for each plane is derived for most influence or combination of stress states. This model has the potential to simulate the behavior of material with anisotropy, fabric pattern, slip planes and crack opening/ closing. The model results under monotonic loading and also different states of cyclic loadings such as uniaxial compression, alternate compression tension, shear and triaxial compression are compared with experimental results that show capability of model.