Role of punching shear reinforcement in the seismic performance of flat slab frames

Horizontal cyclic loading tests of flat slab–column specimens indicate that a considerable enhancement of the drift capacity can be achieved by introducing punching shear reinforcement. However, seismic design codes either do not recommend or do not cover buildings in which flat slabs are part of the primary lateral load resisting system. Nonetheless, flat slabs are popular, even in earthquake-prone areas. The purpose of this paper is to contribute towards a better understanding of the benefits and limitations of using punching shear reinforcement in the seismic performance of such structures. To this end, nonlinear static analyses and a set of fragility functions are derived for two reinforced concrete three story frame models. To minimize modelling uncertainties, the numerical models are calibrated based on two laboratory specimens (one without punching shear reinforcement and the other with headed studs) tested under reversed horizontal cyclic loading. The results show that the performance of the frames can be improved by introducing punching shear reinforcement. However, it is shown that the inherent flexibility of slab–column connections under lateral loading remains a limiting factor even when punching shear reinforcement is provided.