Cyclic behavior of dual-steel beam-to-column welded flange-bolted web connections

Cyclic loading tests on dual-steel beam-to-column welded flange-bolted web connections were conducted to quantify their moment resistance, plastic deformation and energy dissipation capacities. The test program consisted of five one-sided connection specimens, where Q355 grade beams and Q690 grade columns were used, to study the effects of beam-to-column welded flange connection details and panel zone shear strength on the connection seismic performance. Two types of welded connection details were considered; one was the traditional complete-joint-penetration (CJP) welded connections by use of backing bars, and the other type was those with the bottom backing bar further reinforced by a fillet weld. Three column web thicknesses were designed to arrive at strong, intermediate and weak panel zones, respectively. It was found that the CJP weld with the backing bar reinforced only under the bottom beam flange produced satisfactory performance and accommodated plastic rotations larger than 0.03 rad, while a maximum plastic rotation of 0.04 rad could be developed in the high-strength steel panel zone before fracture occurred. These results evidenced that those dual-steel connections could still sustain high seismic deformation demands.