A image plasticity model for structural concrete

Motivated by a requirement to provide a useable model to study the response of pre-stressed concrete nuclear reactor vessels, this paper (i) introduces a new three invariant image associated plasticity model, (ii) describes an efficient stress integration algorithm (which includes automatic sub-incrementation, line searching and the use of auxiliary surfaces within the closest point projection method) and (iii) compares stress path simulations against a series of 67 experimental multiaxial tests from the University of Colorado. The conceptually simple model reproduces the main features of the inelastic response under a range of proportional and non-proportional loading regimes. Error measures for the predictions are smaller than those reported by Ju et al. [Ju JW, Simo JC, Pister KS, Taylor RL. A parameter estimation algorithm for inelastic material models. In: Desai CS et al., editors. Proceedings of the second international conference on constitutive laws for engineering materials: theory and applications, vol. II, Tucson, Arizona, USA, 5–8 January, 1987] for their two-invariant image modified cap model.