Hypothesis for Localized Horizontal Shearing Failure Mechanism of Slender RC Beams

The flexural-shear cracking behavior of RC beams was investigated to get a better understanding of the fundamental nature of the shear failure mechanism. Eight RC beams with special features were tested. Each test specimen was fabricated to artificially isolate or add the effect of a certain factor on the critical shear cracking process. Then the test results were directly compared with those of ordinary beams, and the differences were analyzed. To supplement the experimental investigation, the quantitative response of RC beams with varying amounts of cracking was also examined by utilizing a finite-element method incorporated into a fracture mechanics approach. It was found that the localized horizontal shearing action, which is developed right after the formation of the onset of flexural cracking, had a major responsibility for the flexural-shear failure, and that horizontal cracking along the flexural reinforcement was the prerequisite condition for the propagation of the shear crack into the compression zone of the beam. Based on these observations, an hypothesis of a localized horizontal shearing failure mechanism is presented in terms of initiation and propagation of a critical shear crack. This concept leads to a comprehensive description of the causes and processes of flexural-shear failure in slender RC beams.