The keen purpose of this study is to investigate the seismic performance of buildings equipped with damped-outrigger system using the buckling-restrained brace (BRB) system (BRB-outrigger) and to propose the optimal design recommendation for buildings with a different height. The numerical models with building heights of 72, 144, 216 and 288 m, each contains two layers of BRB-outrigger and a 40 m by 40 m structural plan are analyzed using response spectral analysis (RSA) and nonlinear response history analysis (NLRHA) procedures. To get more closer to the actual reality, the member-by-member benchmark models are designed based on the seismic code requirement. In the response spectral analysis procedure, the equivalent damping ratio is computed in order to include the BRB's inelastic response. For the main purpose of parametric study, a simplified model which will be using a Timoshenko beamcolumn element in order to capture shear-type to flexural-type lateral deformation for a lower to higher raising buildings are proposed. The dimensionless parameters that actually describe the relationships between the core structure stiffness, outrigger flexural stiffness, the axial stiffness of BRB and perimeter column in the parameter study are considered based on practical design and allowable structural sections. The optimization targets include the maximum roof drift, inter-story drift ratio, core structure base shear, core structure overturning moment and the BRB energy dissipation performance. Based on the analyzed result, the ranges of optimal design parameters vary in the different optimization targets and building heights. This study concludes with a design recommendation for building equipped with BRB-outrigger system with different building heights.
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