Shear-critical cracking in slender reinforced concrete beams

This paper describes an experimental investigation into the cause of critic al-shear cracking in slender reinforced concrete beams, using 20 simply sup ported reinforced concrete beams loaded to failure. The basic approach used was that the test beams were specially designed and fabricated to artifici ally isolate or add the effect of a certain factor on the critical-shear cr acking process. Then these test results were compared with results from ord inary control beams, and the differences were analyzed to deduce the major cause for the initiation and the propagation of flexural shear cracking. Th e results indicated that the initiation of flexural shear cracking was stro ngly associated with the bond between concrete and reinforcement. Also, it was found that the propagation of the critical shear crack depended exclusi vely on the intensity of horizontal cracking. Some results were incompatibl e with the concept of shear strength of critical sections that form the bas is of current shear design provisions. A more rational hypothesis of bond-i nduced shear failure mechanism is derived based on these experimental resul ts.