Optimum earthquake-tuned TMDs: Seismic performance and new design concept of balance of split effective modal masses

The present paper, concerning the performance of optimum TMDs in seismic engineering, is composed of two parts. First, Part I deals with a comprehensive investigation on the effectiveness of an optimum seismic-tuned TMD towards reducing the earthquake response of linear frame structures, which is set up by a dedicated optimisation algorithm, allowing to achieve the best control device for a specific structural system and earthquake event. First, a representative set of 16 primary structures and 18 selected earthquakes has been considered, for a total of 288 cases. Second, additional trials based on a benchmark 10-storey frame and on a codified set of far-field earthquakes (FEMA P695 database), composed of 2x—22=44 records, have been developed, for a further assessment. The presented outcomes provide extensive information about the TMD performance in the seismic engineering scenario, for a-priori known seismic input. Then, Part II reports a comprehensive post-processing and interpretation analysis of the results above. Specifically, connections between seismic TMD performance and modal structural properties are envisaged. Cross-comparisons, presented here through typical sample cases, analyse the changes of the structural characteristics after TMD insertion and monitor the associated effects on the seismic response reduction. The crucial role of achieving a balanced split of effective modal masses on the tuned mode is investigated, and highlighted as an essential ingredient to rely on a high TMD effectiveness in the seismic context. This criterion may be implemented within the tuning process, as a basic true structure-based concept for TMD design in Earthquake Engineering applications, thus for a-priori unknown seismic input.