Web reinforcement effects on shear capacity of reinforced high-strength concrete beams

Abstract

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 a/d ratios. The ultimate load capacity of the two types of beam is comparable for a/d < 2. For higher a/d 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.