PLASTIC MODEL FOR CONCRETE IN PLANE-STRESS STATE - I - THEORY

A rate-independent constitutive model for plain concrete on the basis of the bounding surface plasticity theory is formulated. Plastic strai n rate is described by three independent plastic mechanisms without us ing a plastic potential surface. The actual plastic surface degenerate s to the current stress point. The bounding surface shrinks in the pos tcritical state. Separate criteria of loading/unloading are used for t he deviatoric and hydrostatic portions of stress rate. Plastic modulus functions are formulated separately for virgin loading/unloading/relo ading cases on the basis of experimental data. Three different descrip tions of shrinkage of the bounding surface are proposed. The important features of concrete behavior, namely, stiffness degradation, contrac tion/dilatation phenomenon, and different behavior of concrete in comp ression and in tension are satisfactorily rendered by this model. The presented model can describe concrete behavior in the plane stress sta te in the full range of loading including cyclic loadings.