Cyclic Behavior of High-Strength Steel Unstiffened Extended End-Plate Moment Connections

Abstract

The paper presents experimental investigations on the cyclic behavior of unstiffened extended end-plate moment connections fabricated from high-strength steel. Five tests were conducted on connections using conventional (grade Q355, fy = 355 MPa) steel beams and high-strength (grade Q690, fy = 690 MPa) steel columns and end plates. The effects of end plate and column flange thicknesses, and weak panel zone design, were examined, thus resulting in failure modes being either end-plate fracture, bolt rupture, or combined mode. Experimental results are provided in detail, including observations of different failure modes, moment-story drift angle, moment-connection rotation, moment-shear distortion, and moment-beam rotation curves, as well as mechanical indices to characterize cyclic response. The moment resistances of these specimens are compared with Eurocode 3 Part 1-8, indicating consistent predictions. The maximum and cumulative plastic rotations, and cumulative energy dissipation, are evaluated, demonstrating limited plastic rotations (15–25 mrad) of the bolted end-plate but substantial plastic distortion (> 35 mrad) of the panel zone. Hence, the 30% limit on web panel contribution to joint plastic rotation is suggested to be relaxed to 70%. Inelastic response of the panel zone can be well predicted by the Krawinkler model. Thinner column flanges than the end plate of the same steel grade has an adverse affect and should not be used in seismic design.