Optimization of a non-conventional TMD implemented via inter-storey isolation

Inter-storey isolation has gained more and more interest in recent years as an alternative mitigation strategy, effective for new and existing buildings, to base isolation, whenever the latter results to be impractical, technically difficult or uneconomic. The technique consists in implementing a non-conventional Tuned Mass Damper (TMD) via flexible isolators inserted at floor levels along the height of a multi-storey building. An optimal design methodology is proposed in the present paper by ensuring the compatibility between the control function and the resistance and serviceability of the tuned structural masses. Aimed at the global protection of both the structural portions separated by the isolation system, i.e., the substructure and the isolated superstructure, the optimization procedure is based on an energy performance criterion that requires the maximization of the ratio between the energy dissipated in the isolation system and the seismic input energy globally transferred to the entire structure. Numerical simulations, performed under natural accelerograms with different frequency content and considering increasing isolation levels along the height of a reference frame structure, are used to evaluate the seismic performance of the optimized inter-storey isolation systems. The influence of the structural flexibility is investigated and comparisons with base isolation are finally provided.