Multi-objective optimization of the inter-story isolation system used as a structural TMD

Inter-story isolation system (IIS) is increasingly being sought to add floors on top of existing buildings while controlling their base shear forces. One of the main issues with this application is the need to control the drift between the two structural parts and the acceleration of the superstructure, while optimizing the substructure performance. Therefore, this study investigates the use of the IIS as a structural Tuned Mass Damper (TMD), proposing a specific multi-objective optimization approach and providing new design equations for the IIS parameters. Unlike conventional TMD approaches, which focus on the performance of the primary structure (i.e., substructure), the proposed approach aims to consider the overall structural response. The optimal solutions obtained are then compared with the consistent ones currently available in the literature. Finally, time-history analyses of three simple case study structures are performed to validate these optimized solutions. The results demonstrate the potential of the IIS in improving the seismic performance of the substructure, as well as the possibility of limiting the isolation drifts and superstructure accelerations according to specific needs.