An elastoplastic stochastic damage constitutive model for concrete under multidimensional loading

This paper presents a novel multidimensional, elastoplastic, stochastic damage constitutive model for concrete developed through the phenomenological approach, with the aim of providing a more objective description of the mechanical behavior of concrete under multidimensional stress states. First, an isotropic hardening model of concrete was established within the effective stress space based on Ottosen's criterion. This approach ensures that the yield surface remains smooth and continuous, thus preventing potential nonconvergence issues in numerical calculations that may arise due to strain softening. Subsequently, a novel methodology was established, grounded on the non-associative flow criterion of plastic mechanics, to address the issue of plastic deformation in the elastoplastic stochastic damage constitutive model. Finally, the multidimensional, elastoplastic, stochastic damage constitutive model of concrete was imported into COMSOL Multiphysics for a numerical analysis of reinforced concrete (RC) beams without web reinforcement. The obtained results were analyzed and compared with the simulation results derived from ABAQUS in terms of the plastic deformation, damage evolution, and force–displacement curves. The findings indicated that the proposed multidimensional, elastoplastic, stochastic damage constitutive model for concrete could more accurately capture the progression of plastic deformation and comprehensively represent the evolution process of concrete damage under loading conditions when compared with ABAQUS simulations. The force–displacement curve derived from this model exhibited a closer agreement with the experimental data, with the discrepancies between the calculated and tested values of the concentrated loads across various deflections remaining within 10%. The proposed constitutive model effectively encapsulates the nonlinear and stochastic characteristics inherent in concrete.