Abstract:To evaluate the safety against seismic collapse of EBSFs (Eccentrically Braced Steel Frames)

24 representative EBSFs in areas of seismic fortification intensity VIII and IX were designed. Then their capacity against seismic collapse was researched by the CMR (Collapse Margin Ratio) index from IDA (Incremental Dynamic Analysis) based on the automatic control program according to seismic collapse evaluation system of FEMA P695. The results show that EBSF system possesses necessary safety against seismic collapse

the CMRs of EBSFs decrease with the increase of stories (height)

i.e.

higher structures have weaker capacity against seismic collapse

greater collapse probability; the structures in areas of seismic fortification intensity VIII possess larger CMRs and lower collapse risk than those in areas of seismic fortification intensity IX

when subjected to corresponding scarce earthquakes respectively; and the EBSFs with V-shape braces have larger CMRs

thus greater capacity against seismic collapse than those with K-shape braces.