Seismic resistant self-centering steel moment resisting frames with bottom flange friction devices

New earthquake-resistant structural steel moment resisting frame (MRF) systems are being developed by a research group led by Lehigh University in collaboration with Princeton and Purdue Universities under the NSF funded NEESR-SG research program. These innovative self-centering (SC) structural systems are designed to be damage-free under the design basis earthquake (DBE). This paper presents the results of experimental studies on self-centering moment resisting frames (SC-MRFs) with post-tensioned friction connections. The connection consists of a friction device placed below the beam bottom flange, in order to avoid interference with the composite slab, with post-tensioned high strength strands running parallel to the beam. Tests on the connection show it to possess excellent ductility, minimize inelastic deformations in other elements of the connection, and return the structure to its pre-earthquake position.