Seismic performance of buckling-restrained brace outrigger system in various configurations

The outrigger system is deemed an effective solution for mitigating the seismic responses of tall core-tube-type buildings. By incorporating a buckling-restrained brace (BRB) in the outrigger system (BRB-outrigger), the BRB-outrigger reduces seismic response not only through the outrigger mechanism but also through the seismic energy dissipation from the BRB’s hysteretic response. This study investigates the seismic behavior of structures with a single layer BRB-outrigger and proposes three types of BRB-outrigger configurations for practical design purposes that fit different architectural requirements. An analytical model, with heights of 64, 128, 256, and 384 m and different outrigger spans was used to investigate the optimal outrigger elevation and required outrigger stiffness for achieving minimum seismic response using spectral analysis and nonlinear response history analysis. The design indexes and design charts based on the analysis results are proposed for preliminary design. Design examples of structures with different BRB-outrigger configurations utilizing the proposed design charts are demonstrated.