Enhancement of Ductility of Existing Seismic Steel Moment Connections

Abstract

The fracture of beam-to-column connections of steel buildings in the Northridge and Kobe earthquakes generated concerns about the reliability of current design and construction technology for steel connections. The same type of fracturing may occur at similar beam-to-column connections of steel buildings in other seismically active areas. A simple method is proposed here to enhance the ductility of beam-to-column connections of existing buildings. By trimming the bottom flange of the beam slightly, the ductility of the connection can be greatly improved. Experimental studies of the newly designed connections under cyclic load show that the ultimate strengths are almost unaltered; however, the plastic rotational capacity can be increased significantly. When adopting the proposed method, the only work needed is to trim part of the bottom flange plate, and this can be done without removing the floor slab. The proposed connection method can be easily implemented to enhance the ductility of beam-to-column connections of existing buildings.