In 1993 CTA was contacted by the office of Lemessurier Associates, structural engineers, to advise on feelable vibration in a new building under construction. The structure in question was a bridge-like span at an upper level of a multi-story gallery space. Persons standing on this part of the floor felt significant vibration whenever someone walked on the bridge portion of the structure. There was absolutely no danger of collapse, but the owner felt the vibration would be distracting to visitors.

After some calculations to model the effects of adding steel to stiffen the structure, we suggested a tuned-mass damper to control the oscillation of the structure. The damper was highly successful, and the floor response feels like any normal structure. The cost for the tuned-mass damper was well below the other options, and the damper was more effective.

Since that project, we have applied the same concept to several other projects. One of these was a long span staircase in the lobby of a new courthouse. Another project was a convention center with large span floor structures in the function rooms. For the convention center, dampers were included as an integral part of the structural design.