Earthquake failures of welded building connections

This paper presents the circumstances by which a ¯awed connection came to be used in tens of thousands of buildings of modern steel construction in seismic zones. Following the 1994 Northridge, California earthquake, it was found that these welded moment connections could not withstand expected earthquake distortions, and in fact fractured well below the intended design levels. The problem did not result from simple design or construction mistakes, but ultimately from an accumulation of evolutionary ``re®nementsʹʹ in the design, materials and fabrication methods. This paper sheds light on gaps in the cooperative process between academia, professional engineers, and material and equipment providers that have led to tens of billions of dollars in potential repair/retro®t of modern buildings located in seismically active zones. Although millions of dollars have been spent in analyzing and testing this ``simpleʹʹ connection, little consensus has emerged regarding the extent to which each causal variable has contributed to the cracking