A progressive multi-objective optimization framework for synergistic seismic resilience enhancement of buildings

Seismic resilience enhancement requires synergistic goals across multiple earthquake intensity levels while maintaining acceptable economic efficiency. To address this challenge, this study proposes a progressive multi-objective optimization framework integrating energy dissipation device (EDD) placement and nonstructural component (NSC) upgrading for resilience enhancement of buildings. In the first stage, EDD placement under the maximum considered earthquake (MCE) is optimized by simultaneously minimizing a hybrid seismic response index and the number of devices. In the second stage, NSC upgrading strategies are optimized to reduce functional loss and upgrading cost while satisfying functional requirements across service level earthquake, design basis earthquake, and MCE. To further enhance optimization performance, several modifications are incorporated into the NSGA-II algorithm, including hybrid population initialization, offspring uniqueness control, and dynamic constraint thresholds, which collectively improve convergence behavior and population diversity. A comprehensive multi-indicator evaluation is conducted to determine the most effective enhancement scheme. A case study of a teaching building demonstrates that the proposed framework can effectively reduce seismic responses, functional loss, repair cost, casualties, and recovery time while maintaining reasonable economic efficiency. The proposed framework provides an effective and practical strategy for resilience-oriented seismic upgrading and performance enhancement of buildings.