22 M. J. Wesolowsky et al. Table 2.1 Vibration results summary Vibration criteria % of locations meeting vibration criteria VC-A 100% VC-B 53% VC-C 5% The heel drops were conducted to verify the natural frequency of each slab. Based on the natural frequency of the slab, the walking scenario speeds were determined to induce the worst-case response. For example, if the heel drop showed an 8 Hz natural frequency, then a walker would walk at 2 Hz or 120 steps/minute to induce the worst-case response. This represents the fourth sub-harmonic of the natural frequency (e.g., 8 Hz ÷4 =2Hz). For walking scenarios simulating in-room walking, slower walking speeds ranging between 75 and 111 steps/minute were conducted as typically occupants will not walk as fast due to furniture and other obstacles. For walking scenarios simulating corridor walking, where there are expected to be fewer obstacles, faster walking speeds between 111 and 126 steps/minute were conducted. 2.5.2 Equipment To conduct the vibration measurements, the following equipment was used: • LMS SCADAS Mobile or CoCo-80 data acquisition system • PCB 393B04 or 393A03 1 V/g accelerometers • PCB 394C06 accelerometer calibrator 2.5.3 Measurement Results Over 200 walking tests were conducted and compiled. The percentages of measurement locations meeting the different VC levels under consideration are shown in Table 2.1. As can be seen from the results in Table 2.1, all measurement locations were found to meet VC-A or better during all walking scenarios. Note that the percentages shown in Table 2.1 are only based on the measurement locations which were selected based on the locations that are expected to have the most floor motion. Other areas which were not measured, such as those located closer to columns or column lines, are expected to have less floor motion and a better vibration performance than those that were measured. For example, it is not uncommon for bays which measured VC-A in the center of the bay to measure VC-C near the columns. 2.6 Conclusions A combination of vibration control strategies was employed to ensure that the structure under consideration would satisfy the laboratory vibration requirements for a new pharmaceutical facility subjected to footfall-induced vibrations. Based on the results during the commissioning testing to verify the performance of the installed TMDs, all measured locations were found to at least meet the performance target of VC-A when subjected to walking scenarios described. Reference 1. American Institute of Steel Construction: Steel Design Guide 11: Vibrations of Steel-Framed Structural Systems Due to Human Activity, 2nd edn. USA (May 2016)
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