Demand and Supply of Rotational Ductility in Flexible Extended Shear Tab Connections

Extended shear tab connections have a long history in the steel construction industry as a practical solution to many framing problems, such as framing the supported member to the weak axis of a column without the need for coping. Extended shear tab connections were introduced to the AISC Manual in 1992 as they allow greater geometric variation to the counter conventional configuration. The use of extended tab connections, however, comes to a position of concern when the connection flexibility is not satisfied. Higher rigidity of the connection could result in unanticipated moment development in the column that may cause yield mechanism failure due to substantial distortions in the flexible column web or sudden rupture of the bolts or weld. The excess deformation also causes a shift in the connection rotation to the weld centerline, thus limiting the relative end beam rotation. To address these concerns, a parametric study was performed to evaluate the effect of plate thickness, a-distance (distance between bolt line and weld line), skewed angle, number of bolts, and number of bolt columns. These parameters were evaluated in terms of shear strength, corresponding beam end rotation, support rotation, unanticipated moment, and connection failure mechanisms. It was observed that when the tab is connected to flexible supports the connection rotation is partially accommodated by the support, which could result in excessive distortions in the support. The a-distance is the parameter that mostly affects such behavior. Further, connections with multiple bolt columns showed most of their inelastic rotational behavior at the first column of bolts.