Performance-Spectra-Based Seismic Rehabilitation of RC Buildings with Structural Exoskeletons

This paper presents an innovative seismic rehabilitation methodology for reinforced concrete (RC) buildings based on the Performance-Spectra (P-Spectra) approach. The proposed framework enables the efficient design of dissipative exoskeletons-external steel systems mechanically connected to existing structures-to enhance safety, resilience, and sustainability. Unlike conventional retrofit strategies that rely on iterative trial-and-error procedures, the P-Spectra method establishes a direct relationship between target performance objectives and the mechanical properties of braces and dampers. By correlating structural response parameters such as displacements and accelerations with equivalent single-degree-of-freedom systems, the approach allows for precise control of seismic performance and efficient component sizing. The methodology is demonstrated through the retrofit of an RC school building using steel exoskeletons equipped with eccentric braces and steel strip dampers. Nonlinear time-history analyses under spectrum-compatible ground motions confirm substantial reductions in inter-story drifts and peak floor accelerations, and full activation of energy-dissipating devices. The results highlight the P-Spectra approach as a powerful and practical tool for achieving resilient and sustainable seismic retrofits, minimizing disruption during implementation, and supporting the long-term adaptability of critical infrastructure within modern performance-based design frameworks.