Concrete model with normality and sequential identification

To facilitate numerical finite element analysis, it is desirable to endow the constitutive model with normality, associatedness, continuity, convexity and absence of corners. Although these mathematical conditions represent only crude approximations of the actual behavior of concrete, it is of interest to find the best possible constitutive model which meets these conditons. This is one objective of the present paper. The second objective is to develop a model which permits a simple identification of material parameters from test data. The material parameters need not be obtained by simultaneous nonlinear optimization of the fits of all data. Rather, they are obtained in sequence through a precisely defined procedure which involves solving two systems of linear equations. The model describes not only hardening but also post-peak softening under various triaxial stress states. The model agrees well with the available basic test data from monotonic loading tests.