An isotropic damage model based on fracture mechanics for concrete

• An isotropic damage model for quasi-brittle materials is proposed.
• The model is based on fracture mechanics for concrete in terms of fracture energy.
• Strain-softening behavior can be simulated without mesh-size dependency.

This paper presents an isotropic damage model for quasi-brittle materials and demonstrates its performance in crack propagation analysis for concrete. The suggested damage model is based on fracture mechanics for concrete in terms of the fracture energy and is therefore capable of simulating strain-softening behavior without mesh-size dependency. After the cohesive crack model is incorporated into a damage model in a 1D setting, the 1D model is extended to multi-dimensional problems by means of the equivalent strain of the modified von-Mises model. Several numerical examples are presented to examine the fundamental characteristics of the proposed damage model. In particular, we demonstrate that finite element solutions with the damage model are independent of mesh size and that the energy balance evaluated for the fracture process in a three-point bending test for a specimen with a single-edge notch is consistent with the fracture energy. A benchmark test for a mixed-mode fracture is also conducted to demonstrate the performance of the proposed damage model.