Punching shear behavior of HSC & UHPC post tensioned flat slabs – An experimental study

Abstract

Ultra-High-Performance Concrete (UHPC) and High-Strength Concrete are the concretes with superior characteristics comparing with the normal reinforced concrete. Their compressive strength starting with 120 & 60 MPa respectively. The punching shear capacity of posttensioned (UHPC & HSC) flat slabs without non-prestressed reinforcement is experimentally investigated in this research. Five slabs with different concrete compressive strength (100, 120 & 140 MPa) and different strands layout (uniform & bundled & gapped-bundled) were tested under the effect of a monotonic concentric static load. Test results were compared with the provisions of ACI & EC2. The outcomes of the study showed that the punching shear crack occurred at the angles of about 26 & 16° for uniformly and bundled distrusted strands respectively. (HSC) slabs showed good agreement with both ACI & EC2, while (UHPC) slab exceeded the theoretical capacity by about 65%. The bundle & gapped-bundle layout slab showed a slight enhancement in the ultimate punching capacity due to improving the efficiency of used strands, but also showed major reduction in deflection, angle of shear crack and dissipated energy.