Theoretical Analysis and Numerical Simulation of Concrete D-K Model

According to the characteristics of the concrete fracture process zone, a damage and fracture model for concrete, which combines damage mechanics and fracture mechanics is proposed. This model takes the initial fracture damage threshold as the incipient cracking criterion, and takes the unstable fracture toughness as the unstable fracture criteria of crack propagation. With this model, the whole damage and fracture process from initial damage, macro-crack forming to crack unstably propagating can be analysed. Based on the unified strength theory and damage theory, the boundary equations of microcrack generation zone of concrete mode I crack are discussed respectively. Assuming the critical lengths of microcrack generation zone on its propagation direction are equal with the two methodes above, the expression of initial fracture damage threshold is derived. Using numerical method, the crack growth processes of three-point bending concrete beams with and without original cracks are simulated. The feasibility and validity for numerical solving method with damage and fracture model are verified.