An Unstiffened Eight-Bolt Extended End-Plate Moment Connection for Special and Intermediate Moment Frames

Abstract

Bolted extended end-plate (BEEP) moment-resisting connections are prequalified for use in special and intermediate moment frames. The current limits of this prequalification dictate that rolled wide-flange sections with a depth greater than 601 mm (24 in.) necessitate the use of the stiffened eight-bolt extended end-plate connection. The study reported herein experimentally evaluates an unstiffened eight-bolt extended end-plate connection for seismic applications. The connection features a modified bolt arrangement designed to promote uniform distribution of forces across the bolt group. Plastic hinging of the beam is relocated away from the connection joint by heat-treating selected regions of the beam flanges to reduce the strength of steel. Finally, the beam web is reinforced in the expected plastic hinge region to delay strength degradation due to local buckling. The pilot test specimen exceeded the qualifying 4% interstory drift angle. Failure occurred from buckling-induced fracture in the plastic hinge during loading cycles at 6% interstory drift. In this article, details of experimental development and test results are presented and the connection performance is further analyzed through posttest finite-element simulations.