Seismic Assessment of Buckling Restrained Braced Frame Dual System with Special Moment Resisting Frame

Buckling-Restrained Braced Frames (BRBFs) have shown to have appropriate energy–dissipating characteristics, however, low post-yield stiffness of the non-buckling braces cause vulnerability of the structure and seismic defects such as large residual drifts. To mitigate these shortcomings, the Steel Special Moment Resisting Frames (SMRFs) are introduced to BRBFs in a dual system configuration.This paper presents results of a parametric study conducted to investigate the potential benefits of using BRBFs and SMRFs in a dual system. 3 structures have been modeled for comparing the different stiffness proportions of the BRBF and SMRF in dual systems. A bare BRBF and 2 different proportions of stiffness in dual systems have been considered. The 2 dual systems are: 75%-25% structure which the proportions of stiffness in BRBF and SMRF are 75% and 25% respectively. The other structure is 60%-40% model which the proportions of stiffness in BRBF and SMRF are 60% and 40% respectively.The performances of the structures are analyzed by conducting pushover analyses using PERFORM-3D. Analyses demonstrate that adding the Moment Resisting Frames to the BRBF system changes the natural period slightly. Therefore the design base shear will be constant. Also the results of this study show that the 60%-40% model has a better seismic behavior in mid-rise buildings. All the BRBs remain in LS performance level and the secondary system will be mobilized at higher level which may be concerning for bare BRBF system

Keywords:

BRBFs , MRFs , Low Post Yield Stiffness , Dual System , PERFORM-3D