Recently, in Japan, apparent mass dampers using a ball-screw amplifying mechanism have been put to practical use in successful seismic control devices to be incorporated into high-rise buildings. Apparent mass dampers are also referred to as inerters or dynamic masses, and their use in seismic control is being actively investigated in Japan. The authors have developed a seismic control system by arranging viscous damping elements in parallel and supporting spring elements in series with the apparent mass, respectively, in order to obtain a tuned mass damper (TMD) or dynamic vibration absorber (DVA) referred to as tuned viscous mass damper (TVMD) system.

This paper discusses the modal response characteristics of a TVMD seismic control system in which the secondary apparent masses are arranged such that their distribution is proportional to that of the primary stiffness. We also found that the fundamental modes of the undamped primary system are preserved upon adding the secondary system in the seismic control system. This suggests that an accurate approximation of the maximum seismic response of a TVMD seismic control system can be obtained by using the modes of the undamped primary system through spectrum modal analysis.

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