Evaluation of seismic behavior of steel frames constrained with hybrid core buckling-restrained braces

Bucking restrained braced frame (BRBF) is a special type of concentrically braced frames that the braces do not buckle in compression and as a result shows a desirable energy dissipation behavior. However, low post-yield stiffness of these braces causes large residual deformations at high levels of earthquake itensities. The aim of this article is to evaluate the seismic behavior of a new steel structural system known as hybrid buckling-restrained braced frame (HBRBF). Nonlinear static analysis, nonlinear time history analysis and nonlinear incremental dynamic analysis (IDA) methods are used for standard and hybrid core BRBFs with different stories. The average values of seismic behavior factor (R) for HBRBFs are obtained as 10.2 and 14.7 for ultimate limit state and allowable stress design methods, respectively. In order to carry out response history analyses, past earthquakes records were used with different hazard levels. Hybrid buckling-restrained braced frames are shown to have a significant improvement over standard BRBFs in terms of behavior factor and damage measures including inter-story drift ratios and residual displacements.