Evaluation of the Response of Partially Restrained Bolted Beam-to-Column Connection Subjected to Cyclic Pseudo-Static Loads

The structural response of steel moment resisting frames (MRFs) is greatly dependent on the behavior of beam-to-column joints, according to a properly detailed beam-bolts-plates-column structural chain, in light of capacity design principles. A modeling procedure for bolted top-and-seat angle components and connections for potential use in seismic MRFs is presented herein. Although these partially-restrained connection systems have been demonstrated to provide economic savings, they are not currently certified to be used for moment resistance in any major building specification jurisdiction. Examples of full-scale moment resisting connection systems, experimentally tested in past programs, have been numerically analysed, focusing on top-and-seat angle components, which were observed to control the global response of the joint in terms of failure mechanisms, limiting the displacement ductility capacity and dissipation energy capabilities of the whole resisting system. Refined non-linear solid FEM models, accounting for the influence of friction, pretension of bolts, prying and relative slippage of components through highly non-linear contact elements, have been developed to reproduce the cyclic-reversal test protocol.