Bolted Gusset Plate Yielding in Special Concentrically Braced Frames

Abstract

Based on the authors’ recent findings regarding the Whitmore section and the block shear criteria for determining the ultimate tension resistance of a structural steel-bolted gusset plate, a design equation for determining the yielding resistance of a bolted brace-to-gusset connection in a special concentrically braced frame (SCBF) is proposed. The block shear yielding design equation is intended to replace the Whitmore yielding criterion in seismic design and can be readily applied to the hierarchical seismic design procedure and the balanced design procedure (BDP). Verifications against independent laboratory test results and the authors’ finite-element analysis results are used to justify the proposed yielding criterion. The extent of local ductility afforded by the alternative criteria is also discussed. In addition to providing a rational basis for determining the yielding resistance of a bolted gusset plate, the block shear yielding criterion affords a secondary ductile yielding mechanism. It is illustrated through a numerical example that, while in many cases the proposed criterion would lead to yielding resistances of gusset plates similar to those given by the Whitmore criterion, in the balanced design procedure, the present approach enables a rational design outcome that is otherwise not possible using the Whitmore criterion.