Performance of Steel Frame Building which Experienced Intense Ground Motion

Abstract

A two-story, steel moment frame building that was severely damaged during the Northridge earthquake (1994) is studied in detail. Immediately following the earthquake, the building was judged unsafe for occupancy due to a residual displacement of 7.6 cm (3 in.) in the first story. Opening of the exterior facade revealed severe cracking in the moment connections. All connections contained cracks that started in the weld at the bottom flange of the beam and propagated across the column flange and into the column panel zone. Four welded, beam-to-column, moment connections were taken from the building for additional cyclic testing under controlled conditions in the laboratory to evaluate their residual strength and deformation capacity. Results indicate that the badly damaged specimens still have significant residual strength and deformation capacity. All damaged specimens were tested to 3% rotation.