Experimental Investigation of Self-Centering Beams for Moment-Resisting Frames

Abstract

Previously proposed self-centering moment-resisting frames relied on gap opening and closing in the beam–column interface to achieve recentering capability and energy dissipation capacity. The gap-opening mechanism in the connection interface induces deformation incompatibility with floor slabs and can require complex field construction. To address these drawbacks, a new type of self-centering beam (SCB) has recently been developed. The SCB uses high strength posttensioning (PT) strands inside the beam unit to provide recentering capacity and pretensioned bolt frictional devices to dissipate seismic energy. First, the mechanism of this new beam subassembly is explained and the equations governing the global behavior are given. Eleven approximately half-scale tests were conducted to isolate and investigate the effects of design parameters such as initial stress in the PT strands, and slip resistance in the friction device on system strength and stiffness when subjected to quasistatic cyclic loading. After cyclic displacements up to drift levels of 3%, all specimens experienced nearly zero residual drift, and no yielding was identified in the any of the structural members.