Radio towers are frequently installed atop buildings to serve functions related to communications, electric power infrastructure, and disaster management. In the structural design of such towers, ensuring that their fundamental period is sufficiently separated from that of the substructure is imperative to mitigate the risk of excessive amplification of seismic responses. This imposes critical constraints on the design process. Tuned viscous mass dampers (TVMDs) are effective in suppressing resonant vibrations, which significantly reduces seismic responses even when the natural period of the tower is close to that of the substructure. A parametric survey of the ratio of the periods of a tower and a substructure revealed that a considerable reduction in seismic response could be achieved by tuning a TVMD to a higher‐order mode among those exhibiting large relative deformations of the controlled portion. This effect persists even for cases in which the natural periods of the tower and substructure are nearly equal, although such conditions have traditionally posed significant challenges for a structural design. Thus, our findings expand the design flexibility of tower structures.
Miki et al. (Thu,) studied this question.