Plastic-Damage Cap Model with Crack Closure Behavior for Concrete Modeling

Abstract

A new isotropic plastic-damage cap model of concrete is proposed in this study to overcome the limitations (e.g., crack closure behavior) of the existing continuous surface cap (CSC) model in the hydrocode LS-DYNA. The explicit return mapping algorithm of the cutting plane is used in the proposed model to update the plastic behavior of concrete. A scalar damage variable based on the two different damage laws, i.e., brittle damage and ductile damage, is employed to represent different damage mechanisms of concrete under different stress states. Utilizing the concept of effective stress and the hypothesis of strain equivalence decouples the plastic-damage algorithms in the numerical integration process. The principal strain rules are employed to capture the crack closure feature and reversal load-bearing capacity of concrete. The proposed cap model is implemented into LS-DYNA as the user-defined material model. A significant number of simulations are performed to validate the rationality and accuracy of the newly developed plastic-damage cap models. It is found that the proposed plastic-damage cap model not only captures the basic mechanical behaviors and damage modes of concrete under different stress states but also is superior to the existing model in the predictions of the crack closure behavior and reversal load-bearing capacity of concrete under static and impact loadings.