Seismic Behavior of Steel Frame with Hybrid EBF-BRBF Bracing System

Eccentrically braced frames (EBF) as seismic force resisting systems have high ductility and sufficient stiffness so they can have appropriate performance under seismic loads. To improve the performance of EBFs, this paper proposes to keep EBF at the upper stories and replace an EBF of the lowest story with a buckling-restrained braced frame (BRBF). Using this hybrid-braced frame (HBF) in height transmits ductile member from beam to BRB. Consequently, the beam remains elastic at the lowest floor that has large seismic forces. The seismic performance of EBF, BRBF, and HBF in three buildings is studied through nonlinear time history analysis. During the non-linear dynamic analysis, maximum drift ratio and maximum base shear are selected as the main seismic parameters. Analysis results indicate that HBF can improve the seismic behavior of EBF.

Keywords:

hybrid-braced frame (HBF) , nonlinear time history analysis (NTH) , link beam rotation , maXimum roof drift , maXimum base shear.