On the basis of experimental results already reported by others, a new kinematic-hardening and softening model is proposed for plain concrete. The contribution of the paper is that the loading surface here was calibrated at six control points derived from four traditional types of material test. By abandoning the conventional non-associated flow rule, the new proposed model can justify the validity and applicability of the associated flow rule and gives a good prediction on the behaviour of concrete not only in the proportional loading of tension, shear, and compression tests, but also in cyclic loading cases. The model can also predict the softening behaviour of concrete without transferring the loading surface from stress-space to strain-space. Since the associated flow rule can be successfully used, the derived stiffness matrices are symmetrical, thus easing the computation requirement and saving much computer time and cost. Good agreement with a wide range of experimental data has generally been observed.
Theory of inelasticity without loading surface and associated flow rule