Concrete fracture process modeling by combination of extended finite element method and smeared crack approach

Abstract

This study presents a method that couples the extended finite element method (XFEM) and fixed smeared crack model to simulate fracture process in concrete materials. The Griffith energy criterion is utilized to capture the fracture process zone (FPZ) properties and the distributed microcracks inside the FPZ are modeled using fixed smeared crack concept based on the energy dissipated in the FPZ. Jumping in the displacement gradient field is modeled by incorporating XFEM and fixed smeared crack approach as a new term is added to the stiffness matrix. The model predicts the crack opening as well as the crack sliding displacement so it simulates opening and mixed modes of fracture and, full separation in cracks is taken into account although the smeared approach is utilized. The proposed method captures all phases of concrete nonlinear behavior, which are development of FPZ, distribution of microcracks and formation of macrocracks. It is shown that the model improves the spurious stress transfer although the fixed smeared crack concept is used and the stress-locking phenomenon is overcome. In addition, the model is able to simulate the strain softening behavior in mode I and in mixed mode fracture.