Universal Design for Punching Resistance of Concrete Slabs

A general criterion is proposed as a supplement to the most recent ACI 318 Code. The proposed criterion applies to slabs with or without prestressing having vertical or inclined legs of stirrups or headed shear stud reinforcement in a crucifix layout. Yielding of the top flexural reinforcement in a zone above a column can induce punching. This flexure-induced punching can occur when a pattern of yield lines develop a local mechanism. To avoid punching, a minimum amount of top flexural reinforcement is generally required. The structure may be subjected to gravity loads and lateral forces due to wind or earthquake. For the universal design, shear and flexural reinforcements should first satisfy the requirements of an applicable code, then verify that the zone and amount of top flexural reinforcement in two orthogonal directions are adequate.