Advancing the non-local damage approach for reinforced concrete structures: The Extended Gradient Damage Model

Objective simulation of reinforced concrete (RC) structure, which is insensitive to the mesh size and orientation, is still a challenging task in engineering. In response, this study combines the extended gradient damage (EGD) model with energy decomposition, focusing on predicting the failure behavior of RC with openings. The EGD model adopts a strategy of decoupling the cohesive laws and the damage evolution, thus solving the damage unloading problem inherent in the phase-field models and the gradient-enhanced damage models. Additionally, the EGD model allows for the flexible assignment of tensile and shear mechanical properties to materials. This flexibility eliminates the constraint in the fracture phase-field model that requires the tensile fracture energy to equal the shear fracture energy, thereby enabling more accurate predictions of failure in engineering structures. Since the EGD model diffuses the crack into a damage band that spans multiple elements, the prediction results are independent of the mesh size and shape. Complex fracture patterns can also be reproduced through energy decomposition. In order to efficiently model and predict the failure of RC structures, an explicitly parallel numerical algorithm is developed in this study and integrated into the commercial software ABAQUS. Finally, through a series of numerical examples, it is demonstrated that the EGD model can effectively predict the crack path and global response of RC structures.