Numerical characterization of the nonlinear fracture process in concrete

The growth and development of the fracture process zone in plain concrete has been investigated. A fictitious crack model based noniterative numerical scheme is developed to study the fracture characteristics of specimens of different sizes and geometries. Results from numerical studies on four different geometrically similar specimen sizes and two different specimen geometries are reported and discussed. The finite element program developed accommodates linear as well as nonlinear softening laws for the fracture process zone in concrete. It is observed that the process zone reaches a steady state length which is specimen size as well as specimen geometry dependent. As long as the process zone is allowed to develop to its steady state length, the energy absorbed in the process zone appears to be size and geometry independent. Results from tests on three-point bending specimens and compact tension specimens reported in the literature have been compared with the numerical solutions obtained in this investigation. Specimen size and geometry dependence generally observed in these fracture experiments have been duplicated. The numerical model also successfully reproduces many of the other experimentally observed characteristics in the fracture of plain concrete.