Development of a New Steel Moment Connection

Abstract

Steel moment frames are widely used in buildings subjected to lateral loads such as wind and earthquakes. This paper summarizes development of a new economical steel moment connection for use in highly seismic areas. The highly ductile new connection is primarily utilizing ductility of the gusset plate to provide necessary rotational capacity while the entire beam and column being connected remain essentially elastic. Due to the desirable performance of the connection and the flat geometry of the gusset plate, the proposed connection is well-suited to be used in steel and composite special ductile moment frames, special steel shear walls and dual systems of moment frames plus special concentrically braced frames, all currently used in seismic lateral force resistance in buildings. The proposed new moment connection can also be used in resisting gravity loads and lateral forces due to wind. In the proposed gusset plate moment connection, the beam is cut short to leave a distance from the column face where yielding and plastic hinge formation are expected to occur primarily due to in-plane yielding of the gusset plate. The gusset plate can either be directly welded to the column or bolted to the column using an end plate. With careful proportioning and proper detailing, the beam is expected to remain essentially elastic during the cyclic loading and no, or minimum continuity plates will be required for the column panel zone. Extensive nonlinear finite element analyses have been conducted. The results indicated that the connection will be very ductile and performs in a very desirable manner when the moment capacity of the gusset plate divided by the moment capacity of the beam ratio is less than 1.0, the thickness of the gusset plate is equal or greater than 1.25 times the beam web thickness and the free gusset plate length is equal to 4 to 6 times the gusset plate thickness. Based on the observation from the studies summarized herein, the use of “Upset bolts” is recommended for the bolted version, where tension bolts connect the gusset plate to the column.