WEB REINFORCEMENT EFFECTS ON SHEAR CAPACITY OF REINFORCED HIGH-STRENGTH CONCRETE BEAMS

Thirty-two beams made of normal- and high-strength concrete were tested to study the effects of web reinforcement placement on load-carrying capacity. Sixteen beams had stirrup reinforcement only in the shear span (type A beams); the other 16 had web reinforcement only in the flexural span (type B beams). The shear span-to-depth ratio a/d was varied between 0.6 and 3.7; the concrete strength was varied between 31.7 and 93.1 MPa. Test results indicate that for a/d = 2, high-strength concrete beams have more reserve capacity than normal-strength concrete beams. For beams with web reinforcement in the shear span only, the shear reinforcement is more effective for smaller aid ratios. The ultimate load capacity of the two types of beam is comparable for aid < 2. For higher aid ratios, the ultimate load capacity of type A beams is superior to that of type B beams. The ductility of the two types of beam is comparable for a/d = 0.6, but with increasing a/d the ductility of type A beams becomes superior to that of type B beams. Also, a comparison was carried out with ACI, BS 8110 and CEB-FIP, and it is suggested that some of their recommendations be reconsidered.