EXPERIMENTAL VERIFICATION OF CALCULATED VIBRATING MODELS OF GREAT LAVRA BELL TOWER IN LAVRA RESERVE

The purpose of the article is to investigate seismic resistance of the Great Lavra Bell Tower; to study its seismic response to external influences of various origins; to present the results of the spectral analysis of seismic oscillations records; determine to the bell towers own frequencies of vibrations; to analyse the experimental data obtained in the seismic studies; and to compare the results with the theoretical model of vibrations of the bell tower. The Great Lavra Bell Tower is a historic monument of national importance. Built in 1731?1744, it is a four-tower brick octagonal of 96,87 m high domed with a cross and crown. Design/methodology/approach. Measurements of seismic waves were carried out using the accelerometer ZET 048C and velosimeter GURALP CMG-40T on four levels of the bell tower and 10 meters from it. Observation points were located outside the openings in the bearing walls to eliminate background effects from fluctuations of secondary structural elements of the bell tower. Based on the results of calculations and the values of the first three forms of natural oscillations of the facilities, the sample rate of the instrument digital recordings was taken as 100 Hz. Findings. We have obtained three-component seismic recordings of the belfry’s response to the influence of microseismic external noise. We have determined observable oscillation amplitudes and carried out a spectral analysis of speed and acceleration. The results of the field observations agreed in the engineering frequency range of vibrations with the calculated values of the parameters for the mathematical model of the bell tower. We have identified three main peaks that match the value of the natural frequencies of the building and have maximum signal levels at different heights of the building. We have found that the average values of acceleration amplitudes do not increase with increasing altitude of the observation points above the earth’s surface. Practical value/implications. The value of the average velocity amplitudes increases exponentially with increasing altitude of the observation points. The observations agree with theoretical calculations in the engineering frequency range. We have developed a method for periodic examination of the technical condition of the bell tower by checking the stability of the frequency and amplitude of the oscillations registered in certain points of the bell tower. The method does not require long-term technical inspections of the building. Currently Ukraine lacks experience, as well as regulatory and methodological documentation on the use of vibration diagnostics to examine building structures and facilities for their vulnerability to seismic effects. Working out of relevant regulations is urgently needed due to the increased number of unique building structures of complexity category 4?5 with effectclass SS3.