Geometric characteristic of flexural-shear cracks of members without shear reinforcement

For reinforced concrete members without shear reinforcement, the shear failure is characterized by the formation of a critical flexural shear crack. Recently experimental observations making use of Digital Image Correlation (DIC) by many researchers suggested the significance of geometric characteristics and kinematic conditions of critical shear cracks in shear failure. However, limited efforts were reported in literature on the quantification of the geometric characteristics of critical shear cracks. This is mainly due to the lack of understanding of the mechanism of how the flexural shear cracks form. In this paper, the available models in literature for the shear crack trajectory and the underlying theoretical assumptions are reviewed first. Those models include the shear crack model proposed by the authors. Next, the shear crack trajectory models are validated using a collection of shear crack patterns based on the DIC data obtained from the shear failure database from Delft University of Technology. The majority of the crack patterns are from full-scale shear tests of deep beams with an effective depth larger than 1.0 m. The comparison helps us to have a basic understanding of how accurate the available flexural shear crack trajectory models can achieve.