Punching Shear Tests of Slabs with High-Strength Continuous Hoop Reinforcement

Abstract

The punching shear strength of reinforced concrete (RC) slabs with high-strength (Grade 70 ksi [500 MPa] equivalent) continuous hoop shear reinforcement is investigated. Preassembled continuous hoops are used as the shear reinforcement of slabs without engaging in flexural reinforcement. Through punching-shear tests of eight slab specimens, shear strength and failure mode are investigated. Test results show that the continuous hoops successfully increase the shear strength of slabs, provided that anchorage detail is appropriate to ensure yielding of the shear reinforcement. The shear-resisting mechanism in slabs differs depending on the amount of shear reinforcement. In lightly reinforced slabs, the maximum strength occurs early, before yielding of shear reinforcement. On the other hand, in slabs with more shear reinforcement, the maximum strength occurs at a large deflection where the shear reinforcements yield. Based on these results, two strength criteria for punching shear depending on the amount of shear reinforcement are proposed.