Mixed mode criterion for discrete crack propagation through RC shear zones

Shear load is considered as one of the most important actions in the assessment of reinforced concrete structures. Over the last two decades, significant progress has been made in numerical modelling, with a focus on crack propagation in quasi-brittle materials. It is now generally accepted that complex interaction effects governing the shear crack propagation in RC members can only be captured using discrete crack models. The open question remains as to the correct description of the fracture process zone under mixed-mode loading, which would be generally applicable for discrete crack models. Besides the finite-element method, an interesting class of models have emerged in the last decade that use simplifying kinematic assumptions with the goal to derive analytical solution of the governing equilibrium equations. These models are particularly important for improving the engineering assessment rules for shear zones. A similar approach is being proposed in this paper to evaluate the crack propagation and orientation in a shear span. The model uses a novel kinematic approach for evaluating the crack propagation of a shear crack along with a simple crack orientation criterion. Furthermore, the attained maximum shear capacity and the contributions from dowel and aggregate action are reported to see the reliability of the model and a glimpse on the future aspects of the model are also shown. The model will be validated in the long run and the developed criterion will be applied within a novel incremental semi-analytical model of the crack propagation process, efficiently capturing the shear zone kinematics and equilibrium.