Welded-flange-bolted-web connections were damaged during the 1994 Northridge Earthquake. The SAC Steel Project was started to address the problems associated with this damage. The Connection Performance Team completed research on the behavior of a number of connection types. During this research, some issues were found to influence the behavior of many different connection types. These issues are described in this paper. The issues include panel zone yielding, weld process and toughness, web attachment, beam depth and frame geometry, yield stress of the steel, geometry and orientation of the column, composite slabs, local slenderness and unsupported length, temperature, and strain rate. Panel zone yielding is a yield mechanism that contributes to ductility of moment frame connections, but connections with excessive panel zone deformation may have premature connection fracture and reduced ductility. Therefore, panel zone yield deformation must be controlled to have balanced behavior. The web attachment combined with tough welds and improved weld and weld access hole details were needed to improve the ductility of welded flange connections. Beam depth and span length affect the ductility and performance of moment frame connections, but some factors including temperature, strain rate, and local buckling are of secondary importance.
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