Study of the Behavior of Beam-to-Column Moment Connections with Tapered Beams

Steel moment-resisting frames are used as a kind of ductile system to resist earthquake lateral forces. The behavior of rigid beam-to-column connections has a major effect on the behavior of steel moment-resisting frames. In order to provide the required rotational capacity and ductility of connections, some prequalified connections have been proposed in design codes such as the Iranian Building Code (Part 10). In some of the common practices in Iran, a special connection known as tree-column connection is used in which the increasing of the beam section from plastic hinge location to the column’s face is provided by a tapered beam section. This connection is not a prequalified connection, and hence, its behavior has not been investigated comprehensively. In this paper, a parametric study was performed using finite element analysis to determine the most influencing geometrical parameters on the behavior of tapered part in such connections (e.g., height and length of the tapered beam). Furthermore, a tapered moment connection (TMC) specimen was tested experimentally to clarify its cyclic behavior. The results obtained provided the use of vertical stiffeners to indicate satisfactory connection performance (TMC) at nonprismatic lengths that extend from 0.8 to 1.2 maximum beam height