Mechanical Model for Drift-Induced Punching of Slab-Column Connections without Transverse Reinforcement

A mechanical model is presented for predicting the momentrotation relationship of interior slab-column connections without transverse reinforcement when subjected to seismically induced drifts. The model accounts explicitly for the three load-transfer actions between slab and column contributing to the unbalanced moment resistance—that is, eccentric shear, flexure, and torsion. The moment resistance and deformation capacity are deduced from the intersection of the moment-rotation curve with a failure criterion that is based on the Critical Shear Crack Theory and distinguishes between monotonic and cyclic loading conditions. The model predicts both the moment resistance and the deformation capacity of tests found in the literature well. Based on the model predictions, it is shown that the rotation capacity of slab-column connections in flatslab systems decreases with increasing gravity load and increasing effective depth. Larger column size to effective depth ratios lead to increased rotation capacity while the top reinforcement ratio has little influence on the rotation capacity. It is also shown that cyclic loading results in smaller rotation capacities than monotonic loading, which is more pronounced for small gravity loads.