Drift Capacity Models and Shear Strength Degrading Models for Slab-column Connections

Data collected from shake table tests of two, approximately one-third scale, two story flat plate frames utilizing shear reinforcement, as well as data from prior tests, were evaluated to assess the inter-story drift ratios when punching failures occur for reinforced concrete and post-tensioned slab-column connections with and without shear reinforcement. The drift ratios at punching for the shake table specimens were approximately equal to values reported for quasi-static tests of specimens without shear reinforcement. The existing drift capacity model of the slab-column connections was re-examined based on the existing test data and available shear strength degrading models. Typically, these models include two parameters, the displacement ductility at which the shear strength begins to degrade and the rate at which the shear strength degrades. Using tests data, these parameters were determined for the slab-column connections. The revised models allow better prediction of the nominal shear strength of the slab-column connections when flexural yielding occurs, as well as provide a means to assess the need for shear reinforcement based on the slab span-to-thickness ratios.