Extended finite-element analysis of fractures in concrete

Abstract

In this paper an extended finite-element method (X-FEM) that is fully compatible with standard FE program has been formulated based on a virtual node technique. A cohesive crack model that is appropriate for concrete fracture under mixed-mode loading has been integrated into the formulation. The proposed method was implemented into a commercial FE program as a user subroutine, and two benchmark experimental tests were successfully modelled. The numerical robustness and predictive power of the proposed method have been demonstrated by its excellent predictions on arbitrary crack evolution and the associated load–displacement curves. Detailed numerical investigation of the crack wake shielding effects on the fracture loading curves showed that: (a) crack wake shear shielding has little effect on the peak fracture load and its immediate neighbouring softening phase; (b) the initial shear cohesive stiffness has a significant influence on the descending slope of the softening part of the load–CMSD curve; and (c) the shear cohesive strength appears to make the softening phase more stable and to delay the abrupt fracture point.

Meshless smoothed point interpolation methods for damage modelling

“…The beam is characterised by a mixed-mode loading, with an high shear gradient between the fixed constraint and the applied load P. The failure corresponds to a curved crack path, going from the top of the notch to the point of application of the load P. Due to its characteristics, the simulation of such test is difficult with scalar-isotropic damage models, and usually requires more complex approaches, like discrete cracking methods (see, e.g. Oliver et al [2002], Rabczuk and Belytschko [2004], de Borst et al [2004] and Fang et al [2008]), or special treatments for scalar damage models like the non-local approach (see, e.g. Jirásek [2007]), for example.…”