Rotating- and Fixed-Angle Crack Models in Beams Without Transverse Reinforcement

The modified compression field theory (MCFT) was extended to include the slip deformation across the crack based on the fixed-angle crack model, thereby allowing for the noncoincident directions of the principal strain and stress. To investigate the significance of crack modeling on the analysis, a series of tests on beams without transverse reinforcement was predicted by the rotating- and fixed-angle crack models in the MCFT, and the crack friction truss model (CFTM). The results predicted by the fixed-angle MCFT were dependent on the choice of an initial crack angle and the shear friction law, but with an initial crack angle of 45 degrees and the friction law related, the strength predictions improved significantly, comparable with the rotating-angle MCFT and CFTM. Nonetheless, the average strains predicted with the fixed-angle MCFT are still much greater than those from the rotating-angle MCFT due to the inclusion of slip at the crack interface. It is therefore concluded that the inclusion of slip at the crack interface in the MCFT is influential as far as deformation, rather than strength, is concerned.