Based on extensive numerical modeling and measurements the acoustics consultant of the project recommended the stiffening of the frames along with tuned damping of 5 bays of the floor system of a Pharmaceutical laboratory. The floor vibration criterion used was VC-A (50 μm/s RMS in one-third octave bands). The VC criteria take the form of a set of one-third octave band velocity spectra labeled vibration criterion curves VC-A through VC-G, currently published in an IEST (Institute of Environmental Sciences and Technology) Recommended Practice.
Following the applications of supplemental stiffening steel to the existing beams and girders of the target bays, the natural frequencies of the bays were measured and used in tuning 10 tuned mass dampers targeting the first modes of the 5 bays. The TMDs were installed underneath the 5 bays (2 TMDs/bay) by the steel contractor of the project and commissioned/fine-tuned by DEICON.
Following the commissioning, the acoustic consultant conducted the final measurement of the floor system. The measurement revealed that the vibration amplitudes in the bays where the TMDs were installed were reduced significantly from the untreated floor. The bays with TMDs installed all meet the VC-A criterion (50 μm/s RMS) due to typical walkers in the lab area.