Energy-Based CDM Model for Nonlinear Analysis of Confined Concrete

In this paper, a continuum damage mechanics (CDM) based constitutive model appropriate for confined concrete is presented. Basically, the tensile and shear damage variables are adopted to describe the degrading of macro-mechanical properties of concrete, and the corresponding damage criteria are established based on elastoplastic damage energy release rates, which can predict the enhancement of strength and ductility of concrete under biaxial compression. To describe the compressive consolidation mechanism under triaxial compressive confinement, the above Drucker-Prager type shear damage criterion is modified to take the third invariant of effective stress into account. The irreversible plastic strains are determined empirically in this paper, though the effective stress space plasticity method is also introduced here. Comparing to experimental tests of concrete under biaxial and triaxial compressive stress states, the predictive results of proposed model show good agreement with test data, which validate the capability of present model for reproducing the nonlinearity of confined concrete.