A Novel Steel Beam–Column Connection with Peanut-Shaped Perforated FCPs: Experimental and Numerical Studies

Abstract To improve the seismic performance and achieve postearthquake functional recoverability of steel beam–column connections, this paper proposes a novel connection equipped with flange cover plates (FCPs) featuring peanut-shaped perforations based on the concepts of damage control and negative Poisson’s ratio design. The proposed connection incorporates periodically arranged peanut-shaped perforations on the FCPs. By utilizing the deformation characteristic of the perforations, which contract under compression and expand under tension, the connection effectively suppresses out-of-plane buckling of the FCPs, thereby delaying strength and stiffness degradation while confining the plastic hinge within the replaceable FCPs. Cyclic loading tests were conducted on five specimens to compare the hysteretic response, failure modes, ductility, and energy dissipation capacity of connections with peanut-shaped perforated FCPs against connections with traditional dog-bone weakened FCPs. Finite element analysis was systematically employed to investigate the influence of parameters such as FCP thickness, peanut-shaped perforation geometry, and perforation layout on the connections’ performance. Experimental and numerical results indicate that the novel connection exhibited a plumper hysteretic curve, higher cumulative energy dissipation (26.4% greater than the traditional connection), and good low-cycle fatigue performance. To balance damage control and load-carrying capacity, the vertical perforation ratio of the FCPs is recommended to be 0.6–0.75, and the horizontal perforation ratio 0.4–0.6. Furthermore, a yield-strength calculation formula is derived, and a systematic design procedure was established, providing a theoretical basis and practical guidance for the engineering application of such repairable connections.