Experiments and Analysis of Unstiffened Eight-Bolt End-Plate Moment Connections for Seismic Applications

Abstract

Bolted extended end-plate (BEEP) moment connections are one of several types of connections prequalified for use in special and intermediate moment frames in the ANSI/AISC 358 standard. The BEEP connections that are prequalified include a stiffened and unstiffened four-bolt configuration and a stiffened eight-bolt configuration. In this study, a recently proposed unstiffened eight-bolt configuration is evaluated through large-scale testing and detailed finite-element (FE) analysis. The connection features a modified bolt arrangement to improve bolt force distribution and eliminates the stress concentration from the end-plate stiffener that has led to brittle beam flange fractures in recent studies. In all tests, the proposed connection attained the ANSI/AISC 341 qualifying 4% story drift requirement and exhibited a ductile failure mode, namely, local buckling in the beam plastic hinge and gradual strength degradation. A detailed FE model of the proposed connection is validated against the experimental data and used to further analyze and optimize the connection through parametric studies. Finally, a design procedure which parallels that in chapter 6 of the ANSI/AISC 358 for existing BEEP connections is proposed. A central aspect of the design procedure is a method to calculate bolt forces, including the effects of prying, in the proposed connection.