Single and multiple TMD optimization to control seismic response of nonlinear structures

Tuned mass dampers (TMDs) are control devices used for supplemental energy dissipation in civil structures. In the case of structures that exhibit a nonlinear dynamic response under seismic action, their performance is affected by both the duration of the dynamic excitation and the detuning effect. In order to improve the TMD effectiveness in this scenario, the parameters of three different TMD configurations are optimized in the present work using the particle swarm algorithm. In the optimization process, two different objective functions are considered. The performance of the three optimal TMD configurations is evaluated on three single-degree-of-freedom structures with different fundamental periods subjected to a set of far-field records and a set of near-fault ground motions with strong velocity pulses. From the results of this analysis, it is found that in general, the configuration with two TMDs in series tuned to a frequency of 50% of the fundamental frequency of the healthy structure obtained the highest effectiveness when the ductility demand is greater than 5. In the case of medium-period structures with the highest ductility demand imposed by far-field ground motions, a reduction in the median ductility demand of 26% is achieved with a mass ratio of 25%. A lower effectiveness is observed against near-fault records, especially in short-period structures. Finally, the effect of the optimized TMD on multi-degree-of-freedom structures is analyzed.