Pushover Analysis of Flat Slab Buildings with Shear Studs Punching Reinforcement

Low energy dissipation, punching shear failures and the high lateral flexibility are among the main reasons why it is not recommended to use flat slabs as primary seismic elements in buildings. Punching failures can lead to progressive collapse of the entire building if integrity reinforcement is not provided. Meanwhile, several experimental campaigns have shown that flat slab specimens with enhancement of the punching shear strength via shear reinforcement can achieve considerably large drifts when subjected to horizontal loads. The purpose of this study is to investigate the effect of such drift capacity enhancement in the overall behavior of regular flat slab buildings towards seismic actions. Pushover analyses of buildings with and without shear reinforcement, with 1, 3 and 5 stories and different column cross sections are presented. The unbalanced moment – drift relationships of the slab – column connections are calibrated based on an experimental campaign performed at Universidade NOVA de Lisboa. A simple model, similar to models previously reported in literature, is used to represent the unbalanced moment transfer mechanism by dropping the unbalanced moment to a low value when the joint rotation reaches the experimentally observed value. The presence of shear reinforcement considerably influences the global response of the models. However, several deficiencies in the seismic behavior of the models are observed, even in models where the flat slabs sustain large drift ratios.