Seismic resilient self-centering braces for orthogonal steel exoskeleton structures

External sub-structures, such as steel exoskeletons, have emerged as effective retrofitting solutions by incorporating controlled rocking and post-tensioning to enable self-centering. Shape memory alloys (SMAs) provide an alternative approach, offering flag-shaped hysteresis loops that combine high energy dissipation with shape recovery after large strains. This paper investigates orthogonal dissipative exoskeletons equipped with SMA dampers for retrofitting reinforced concrete buildings. A design strategy is proposed to optimize the dampers for both energy dissipation and self-centering performance. Nonlinear time-history analyses confirm the effectiveness of this approach, showing significant energy dissipation at lower stories and minimal residual drifts, which enhance seismic resilience and support rapid post-earthquake recovery.