Abstract

Outrigger systems incorporating buckling-restrained braces (BRBs) can improve the seismic performance and resilience of tall buildings by combining lateral stiffness enhancement with supplemental energy dissipation. However, determining the effective number, elevation, and stiffness distribution of outrigger–BRBs remains computationally demanding when many possible configurations are considered. This study proposes a computationally efficient power-based sequential optimization approach for identifying effective outrigger–BRB placement and stiffness allocation in tall building systems. A nine-zone finite element benchmark model, developed in MATLAB based on a previously tested structural configuration, is used to examine the proposed method through nonlinear time-history analysis under the 1940 El Centro ground motion. The optimization procedure incrementally allocates BRB stiffness to candidate outrigger locations and selects the configuration that minimizes the maximum inter-story drift ratio at each step. The results are compared with a complete combinational reference search within the selected candidate space to assess whether the proposed procedure can identify optimal or near-optimal configurations with fewer nonlinear analyses. The findings show that the proposed method can reproduce the main effective outrigger–BRB placement patterns while reducing the number of required analyses within the investigated benchmark problem. The results also indicate that BRB stiffness limits influence the distribution of stiffness along the building height and promote more gradual drift reduction. Although the numerical investigation is limited to a benchmark model and a single seismic input, the proposed framework provides a practical basis for preliminary design, rapid parametric assessment, and future extension to multi-record and multi-objective optimization of outrigger–BRB systems.

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