Shear-critical cracking in slender reinforced concrete beams

This paper describes an experimental investigation into the cause of critical-shear cracking in slender reinforced concrete beams, using 20 simply supported reinforced concrete beams loaded to failure. The basic approach used was that the test beams were specially designed and fabricated to artificially isolate or add the effect of a certain factor on the critical-shear cracking process. Then these test results were compared with results from ordinary control beams, and the differences were analyzed to deduce the major cause for the initiation and the propagation of flexural shear cracking. The results indicated that the initiation of flexural shear cracking was strongly associated with the bond between concrete and reinforcement. Also, it was found that the propagation of the critical shear crack depended exclusively on the intensity of horizontal cracking. Some results were incompatible with the concept of shear strength of critical sections that form the basis of current shear design provisions. A more rational hypothesis of bond-induced shear failure mechanism is derived based on these experimental results.