Stress Singularity Effect on Beam Flanges in Moment Connections

Abstract

The ductility capacity of the directly welded flange connection was found to be insufficient after the 1994 Northridge earthquake. The Enlarged End Section (EES) connection which considers the stress singularity effect on beam flanges can be utilized as a means to improve the performance of welded moment connections. The corner of a steel plate contains stress singularities (unbounded stresses) when the corner is bounded by free-free edges and when the angle of the corner is larger than 180°. Also, the corner of a steel plate contains stress singularities when the corner is bounded by fixed-free edges and when the angle of the corner is larger than 61.3°. Nonlinear static finite element analyses of two types of beam-to-column moment connections were conducted. These two types of connections are (1) the constant-beam-section connection, and (2) the Enlarged End Section connection. The result of the finite element analyses shows that the Enlarged End Section connection exhibits much higher strength and ductility capacities.