Multiaxial stress analysis of elastic-plastic damaging concrete structures

A new combined plastic-hardening-damage criterion for concrete is described and its applications analysed. The model, starting from the definition of an internal energy functional and from an elastic limit envelope, associated to the onset of the propagation of defects and microcracks in the material, is able to predict the failure domain and the relevant extension of damage. Three yield criteria are used: a damage criterion, a cap for the hydrostatic compression, that predicts even for isotropic compression the insur-gence of non-linear phenomena and a plastic yield mode, that account for the irreversible deformation that develops in multiaxial stress states. The latter is an extension of the four parameter function proposed by Ottosen, based on the stress invariants I 1, J2, J3, adequately coupled with hardening and damage. The application of the model to the structural analysis of continuum models is performed by means of a viscoplastic regularisation, whose properties are discussed in the paper.