Effects of In-Plane Lateral Restraint and Post-Punching Capacity on Load-Carrying Capacity of Slab-Column Connections against Disproportionate Collapse

The overall goal of this research is to evaluate the potential of disproportionate collapse in older, reinforced concrete, flat plate buildings subjected to the loss of a supporting column. The research program considers testing of isolated slab-column connections that represent the connection near the lost supporting column. The goal of the tests is to evaluate the effects of in-plane lateral restraint and post-punching capacity. The experiments provide critical data for validating the mechanical model of slab-column connections used to examine the disproportionate collapse resistance of the flat plate system. Five tests of restrained and unrestrained isolated slab column tests have been conducted at reinforcement ratios of 1.0% and 0.67%. The tests show that there is a marginal increase in punching shear capacity (2 to15%) due to the in-plane restraint, but is highly dependent in the level of lateral restraint. The tests also show that there can be significant post-punching capacity if the top bars are well anchored into the slab.