Punching Shear Resistance of High Strength Concrete Flat Slabs Reinforced with Steel Fibers and Transverse Reinforcement

The paper presents the results of an investigation about the behavior of reinforced concrete flat slabs made with high strength concrete, steel fibers and ordinary shear reinforcement. We tested twelve flat slabs made with different combinations of high strength concrete, ordinary strength concrete, shear reinforcement and steel fiber volume fraction (0%, 0.75% and 1.5%). The square-shaped slabs were designed to represent the slab-column connection in an interior column. A significant increase in the punching shear strength was observed, due to the use of high strength concrete and the addition of steel fibers. The combination of high strength concrete with 1.5% fiber volume fraction and shear reinforcement provided twice the punching shear resistance of an ordinary strength concrete slab without shear reinforcement and without fibers. Fiber addition is believed to be responsible for an increase of approximately 50% in the resistance and also for an increase in ductility. Comparisons with theoretical code provisions, including CEB/90, ACI-318/89 and Eurocode 2, are presented.