Nonlocal strain-softening model of quasi-brittle materials using boundary element method

The strain-softening localization problems have been studied intensively using the finite element methods. This paper addresses the localization using the boundary element approach. A plasticity model with yield limit degradation is implemented in a boundary element program to study the fracture behavior of quasi-brittle materials. A special integration algorithm is formulated and applied to deal with the singular integrations encountered in the volume integrals over the internal cells where strain-softening occurs. Strain-softening damage localizations are investigated. It is found that as different cell meshes are used in the analysis, the strain-softening region tends to localize into a zone of one cell width, which leads to incorrect results. A nonlocal strain-softening localization limiter is incorporated into the boundary element analysis to avoid the localization problems and attain realistic results.