Measurement of the vibrational frequencies of the long education building (A/2-A/1-A/3) of the University of Miskolc by LDV method

Abstract

The transversal vibrations of the long education building (A/2‑A/1‑A/3) of the University of Miskolc were measured by an LDV (Laser Doppler Vibrometer) interferometer. These very weak vibrations (less than 1 µm amplitude) are generated by ambient sources (including indoor human activities). The measurements were made inside the building on supporting walls; the device was on an anti-vibration table. In the case of 7 measuring points, the averages of one-hour frequency spectra (on work days); at the other 9 points, the averages of 24‑hour frequency spectra (on work days) are shown. The majority of measure-ments were made on the top floor, where the 2.8 Hz vibration, which is characteristic of the complete building, has the maximal amplitude. Going downwards in the building, this amplitude decreases to zero at ground level. The amplitude of the vibrations around 7 Hz, identified as the vibrations of building parts, has a maximum at the intermediate floors.