Cages of Inclined Stirrups as Shear Reinforcement for Ductility of Flat Slabs

The provisions for design of shear reinforcement for flat slabs in the ACI 318 and Eurocode 2 building codes assume that punching failure and flexural failure can be treated as two mutually independent failure modes. However, if the flexural reinforcement yields, then wide flexural cracks will worsen the anchoring conditions for the shear reinforcement and a flexurally initiated punching failure may occur: However, shear reinforcement in the form of inclined stirrups is found to be effective even when wide flexural cracks develop and will, therefore, provide increased capacity and ductility when compared to a design with conventional shear reinforcement. Test results and design recommendations for ductile behavior as well as for maximum punching capacity are presented.