Spectral analysis of structural deformation – A case study

Abstract

Building structures are extremely sensitive to the influence of outdoor conditions. The most frequent types of outdoor conditions are the influence of wind, sunshine, changes in the temperature of a building's surroundings and, lastly, the effect of a buildings own loading or the improper loading by another source. According to the resonance of the structure with its surroundings, vibrations and oscillations at relatively high frequency intervals (0.1–100.0 Hz) also occur. These phenomena significantly affect the static and dynamic characteristics of structures, as well as their safety and functionality. The paper provides an example of the monitoring of these phenomena using geodetic methods at two different types of structures. The first example is an industrial structure with a cylindrical shape, the monitoring of which was made by a total station with a measuring frequency of approximately 2 Hz. The second example is the Apollo Bridge on the Danube in Bratislava (Slovakia), the steel structure of which was measured by acceleration sensors with a frequency of up to 10 Hz. The central aim of the paper is an analysis of the dynamic behavior of both structures using spectral analysis methods. The use of the Fast Fourier Transform (FFT) and the Lomb–Scargle periodogram is described; the structure's own frequencies and the amplitudes of the structure's oscillations are calculated.