Seismic Performance Analysis Of High-rise Buckling-restrained Braced Steel Frames

Buckling-restrained braces(BRB) and infilled walls are widely used in all kindsof structures. Buckling-restrained braces are able to dissipate part of the energyinduced by earthquakes, which will result in the reduction of the main structure.Resently years there have been great development achieved in the research of BRBs.Infilled walls exist in almost all the low-rise and high-rise buildings. Whileperforming as the basic components for architictural use, infilled walls affect theearthquake resistant behaviour of the structure significantly. With the process ofurbanization, heights of buildings are growing up. And because of the anvantages inconstruction speed, available space and earthquake resistant behaviour, along withthe support from the government recent years, steel structure is more and morepopular. Now there have been a lot of design procedures available for BRB, most ofwhich is proposed for low-rise structures. And research on infilled walls isconcentrated on low-rise structures, too. All these factor will block the way onwhich steel structure go into further application. According to the reasons referedabove, works listed below were carried out.1. Typical design procedure for BRB and experiments information carried outin recent years are summarized, which indicate that the buckling-restrained ratio isnot taken along with the results acquired from the theory, but much larger ones.According to the parameter analysis results, the restraining stiffness provided byconcrete is large enough to be considered. To achieve a economic design, it issuggested that restraining stiffness provided by concrete should be considered andbuckling-restrained ratio should be decreased.2. Comprehensive seismic performance analysis on the buckling-restrainedbraced frames that are designed into different lateral stiffness ratio according tothe lateral stiffness ratio design procedure is careied out, where BRBs areconsidered as a kind of energy dissipated components. A appropriatebuckling-restrained ratio is acquired accordingly. As represented in the time historyanalysis, buckling-restrained braced frame perform excellent collapse resistantcapacity under earthquake, whose intensity exceeds the seismic fortificationintensity.3. According to the collapse margin ratio(CMR) method, which is based onIDA procedure, a contrast study is carried out between a buckling-restrained bracedframe and a same frame infilled with autoclaved aerated concrete masonry walls.The results lead to a conclusion that buckling-restrained braced frame infilled with autoclaved aerated concrete masonry walls will perform better on lateral stiffnessand ductility.4. The performance evaluation results provided by the CMR method underChinese seismic provisions are too conservative to put into application. Aftertransform the design requirements into US seismic provisions, A contrast studybetween the structures mentioned above is made according to the CMR basedcomprehensive evaluation methods raised in FEMA P695. The results show that thebuckling-restrained braced frame performed to be not reliable on collapse resistantcapacity, and the buckling-restrained braced frame infilled with autoclaved aeratedconcrete masonry walls provides reliable collapse resistant capacity in theunexpected intensity earthquake.