After the Hyogoken Nambu Earthquake, January 17, 1995 and the Northridge Earthquake, January 17, 1994, fracture behavior was observed in many steel buildings at their welded connections between beams and columns, structural members and other structural components. In earthquake-resistant design criteria, of buildings, plastic deformations are permitted to absorb the seismic energy, while fractures are unacceptable. Therefore the response properties of a frame which undergoes fracture type collapse behavior have not been investigated. It is necessary to investigate the response properties in order to evaluate the earthquake resistance capacity of a frame taking account of the possibility of brittle fractures. In this paper, seismic response analyses, considering the effects of brittle fractures at beam-ends during an earthquake excitation, are carried out for steel frames. The response properties are compared to those of ductile frames and the effects of fractures on the seismic response of steel frames are discussed.
