Behaviour of steel moment connections with a single flange rib

This paper presents a study of flange rib moment connections for use in steel moment-resisting frames. The connections are strengthened by welding a vertical rib to the beam flange and the column flange. The rib is characterized by an extension. Finite element analysis and experiments were conducted to elucidate the behaviour of lengthened rib reinforced connections. The results of the finite element analysis established the effectiveness of the lengthened rib in mitigating local stress concentrations and forming the plastic hinge zone in the beam. Two full-scale proof-test specimens behaved as observed by the analysis, and exhibited greater than 3% radians of plastic rotation under cyclic load. Without brittle fracture, both specimens developed a plastic hinge in the beam. Extensive yielding and local buckling occurred in the beam flanges and the web. The connections strengthened with a single flange rib were successfully verified by the test.