Modern Strengthening Strategies for Steel Moment Resisting Frames: State – of – the – Art –Review

Abstract

The Northridge (1994) and Kobe (1995) earthquakes caused widespread brittle fracture in the connections of steel moment-resisting frames. As a response to this unexpected damage, a variety of new designs have been proposed. Among many connections investigated recently, two categories of connections are mostly used to enhance ductility under severe earthquake loads. One of the two categories is the reinforced connections, in which the cover plate or haunch are used to strengthen the connections. The other category is the reduced beam section (RBS) connections. In present paper recent studies of strengthening strategies or reinforced connections are discussed. In this design philosophy, the portion of the beam adjacent to the column, where the maximum moment occurs during seismic loading, is strengthened. This will force the plastic hinge to form away from the joint. The strengthening may be done using: haunches cover plates, rib plates, side plates…etc.

Keywords: Strengthening schemes, reinforced connections, cover plates, rib plates, side plates, haunches