Nonprismatic Beam Element for Beams with RBS Connections in Steel Moment Frames

Abstract

This paper presents the development of a nonprismatic beam element for modeling the elastic behavior of steel beams with reduced beam section (RBS) connections. The accuracy of this element is evaluated by comparisons with finite element solutions. A simplified approach is also suggested, which uses a prismatic beam element to model beams with RBS connections. The effect of the RBS on the elastic stiffness of beams and frames is then investigated through a series of parametric studies, and by analysis of 3-, 9-, and 20-story moment frames. With a 50% flange reduction, the increase in maximum story drift ranges from 6 to 8% for typical moment frame buildings. With a 40% reduction, the increase in maximum story drift is 4.5–6%.