偏心支撑钢框架抗地震倒塌富余度研究

Research on Seismic Collapse Margin Ratio of EBSF System

按中国规范设计了有代表性的8、9度抗震设防的偏心支撑钢框架共计24个,采用增量动力分析倒塌分析方法,以倒塌富余度为衡量指标,按照FEMA P695评估体系对该结构体系的抗地震倒塌安全性进行研究。结果表明:K形、V形偏心支撑钢框架满足FEMA P695对倒塌富余度的要求,拥有必要的抗地震倒塌能力;结构倒塌富余度随结构层数(高度)增加而减小,高度越大的结构抗地震倒塌性能越差,遭遇强烈地震时倒塌概率越大;在遭受各自对应的罕遇地震时,8度设防区的结构比9度设防区的结构拥有更大的倒塌富余度,倒塌风险更低;V形偏心支撑钢框架比K形偏心支撑钢框架拥有更大的倒塌富余度。

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 showed 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.