Cyclic tests on nine full-scale beam-column subassemblages were carried out in support of thedevelopment of a new lateral load-resisting system recently introduced in AISI-S110: Standardfor Seismic Design of Cold-Formed Steel Structural Systems-Special Bolted Moment Frames.With double channel beams and HSS columns interconnected by bearing-type high-strengthbolts, all specimens showed an story drift capacity significantly larger than 0.04 radian. Typicalresponse is characterized by a linear response, a slip range, followed by a significant hardeningregion due to bolt bearing. Three failure modes were identified. Confining in the connectionregion, inelastic action through bolt slippage and bearing is ductile and desirable. Such inelasticaction always occurs first, but either column or beam may also experience buckling. Beambuckling is most undesirable due to significant post-buckling strength degradation. Extendingthe concept of instantaneous center of rotation of an eccentrically loaded bolt group, a model thatcan reliably simulate the cyclic behavior of the bolted moment connection is presented.
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