Cyclic Behavior of Steel Moment-Resisting Connections Reinforced by Alternative Column Stiffener Details II

Lee, Daeyong; Cotton, Sean C.; Hajjar, Jerome F.; Dexter, Robert J.; Ye, Yanqun (2005). "Cyclic Behavior of Steel Moment-Resisting Connections Reinforced by Alternative Column Stiffener Details II," Engineering Journal, American Institute of Steel Construction, Vol. 42, pp. 215-238.

A study has been conducted to reassess the current AISC seismic panel zone design criteria for the Welded Unreinforced Flange-Welded Web (WUF-W) steel moment-resisting connections and to investigate acceptable minimum seismic panel zone design criteria for moment-resisting connections. Five full-scale WUF-W cruciform specimens were tested in this research, coupled with corroborating nonlinear finite element analysis. All had relatively weak panel zones designed to cause large localized strain concentrations in the girder flange-to-column flange connection region and to exceed the panel zone shear deformation of the 4gy (in other words, four times the panel zone shear yield strain, gy). This paper presents the cyclic panel zone behavior of the WUF-W cruciform specimens and an assessment of the current AISC seismic panel zone design criteria for these connections. Two possible modifications for seismic panel zone design criteria are then proposed and verified against these tests as well as experiments from the literature. One equation provides a more accurate assessment of panel zone nominal strength for steel moment-resisting connections, and the second equation provides a panel zone required strength equation that targets permitting up to 8gy panel zone shear deformation for WUF-W and similar connections.