Integration algorithms for concrete plasticity

Presents a computational algorithm for the numerical integration of triaxial concrete plasticity formulations. The specific material formulation at hand is the so-called extended leon model for concrete. It is based on the flow theory of plasticity which entails isotropic hardening as well as fracture energy-based softening in addition to non-associated plastic flow. The numerical algorithm resorts to implicit integration according to the backward Euler strategy that enforces plastic consistency according to the closes-point-projection method (generalized radial-return strategy). Numerical simulations illustrate the overall performance of the proposed algorithm and the significant increase of the convergence rate when the algorithmic tangent is used in place of the continuum operator.