Forensic studies of a large cover‐plate steel moment‐resisting connection

A large-size, single-sided cover plate connection composed of a built-up BW36×670 column and a W36×359 rolled beam section was tested in a custom-made test fixture using the SAC Phase I loading protocol. A trapezoidal plate was used as top flange reinforcement and a rectangular plate was used as bottom flange reinforcement. The test specimen failed catastrophically at a story drift angle of 1.7% and a beam plastic rotation of 0.009 radian by fracture through the beam top flange and beam web. An ABAQUS nonlinear finite element model of the connection was prepared and analyzed. The ABAQUS data indicate that the likelihood of brittle or ductile fracture at the observed crack initiation site is very low. Fractographic and microstructure studies were conducted after testing. The fractographic analysis of the failure surface showed that the fracture initiated at the toe of a fillet weld that joined the top cover plate to the beam flange. The microstructure analysis around the crack initiation site revealed laminations in the base metal at the crack initiation site. Copyright © 2002 John Wiley & Sons, Ltd.