Seismic behavior of slab-column connections

Abstract

Brittle punching failure of flat plates can occur as a result of transfer of shearing forces and unbalanced moments between slabs and columns. During an earthquake, the unbalanced moments transferred between slabs and columns can produce significant shear stresses that increase the likelihood of brittle failure. This brittle punching failure mode must be avoided for seismic-resistant flat plate structures. The most common punching strengthening methods are provision of the slab-column connections with drop panels or shear reinforcement or use of high strength concrete in the slab at the vicinity of the connections. This paper compares the effect of these punching strengthening methods on the ductility of slab-column connections. The results of a part of an extensive experimental program conducted on edge slab-column connections, without and with shear reinforcement, are presented. The experiments show that provision of stud shear reinforcement results in seismic-resistant slab-column connections, in which brittle punching failure is avoided in severe earthquakes. The connections with stud shear reinforcement can undergo ductile deformations associated with up to 5% lateral interstorey drift ratio, without loss of resistance to punching due to gravity loads. Key words: concrete design, ductility, energy dissipation, flat slabs, lateral drift, moment transfer, punching, seismic, shear strength, slab-column connections, stiffness, stud shear reinforcement.