Effective damping ratio enhancement effect of tuned inerter dampers for seismic response control of civil structures.

• The analytical expression of the TID effective damping ratio is derived under the hypothesis of white-noise seismic excitations. • The effective damping ratio enhancement (EDRE) effect of TID is investigated for seismic response control of civil structures. • The theoretical formula of TID optimal design parameters is proposed based on the EDRE effect for both damped and undamped primary structures. Tuned inerter dampers (TIDs) are widely recognized as promising inerter-based devices for controlling the seismic response of civil structures. However, the effective damping ratio enhancement (EDRE) effect of a TID has not been investigated thoroughly. In this study, the TID control effectiveness is considered as the effective damping ratio (EDR) applied to the main structure, and the analytical expression of the EDR is derived based on the white-noise seismic excitation hypothesis. The theory of the EDRE effect is introduced to explain the superior control effectiveness of a TID to that of a bare dashpot. Theoretical formulas of TID optimum parameters are proposed based on the EDRE effect for both damped and undamped main structures. These formulas ensure that the optimum control effectiveness and EDRE effect of a TID are achieved simultaneously. For this purpose, the TID is supposed to provide the highest EDR with the lowest damping ratio cost for the optimum EDRE effect. Compared to another well-known inerter-based device, i.e., a tuned viscous mass damper, a TID is particularly recommended when the damping ratio is restricted to less than 0.03. Moreover, the TID control effectiveness and EDRE effect are verified numerically under real seismic ground motions recommended by ATC-40. The numerical analysis results show that the TID is effective in controlling the structural seismic response, primarily because of its good performance in suppressing the system input energy. [ABSTRACT FROM AUTHOR]