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Publicly Available Published by De Gruyter July 15, 2007

Detection of tidal signals on large objects and in their surroundings

  • Gyula Mentes

Nowadays the stability investigation of large objects, such as towers, buildings, bridges, etc. without disturbing their function plays a very important role in disaster prevention. For detection of structural damages dynamic testing methods using artificial exciting signals are carried out commonly. Sometimes natural effects (wind, micro-seismic vibrations) are utilized as input signals. For health and earthquake risk assessment of large, dangerous objects a steady, periodical exciting signal is much more advantageous than occasional effects, e.g. wind blasts or micro-seismic vibrations with statistical characteristics. Due to the tidal phenomena of the Earth the solid Earth crust is periodically deformed. The tidal effect can be calculated from the astronomical parameters of celestial bodies (Moon, Sun and planets). In a normal case the Earth tide can only be measured by means of very high sensitive instruments in deep observatories built in the bedrock but not on the surface in sediments or soils. In special cases the large objects, as high towers, large buildings, long bridges, etc. gain the tidal deformations like a vertical pendulum and transfer these movements to the surrounding ground. These increased deformations can be measured on the objects and in their surroundings by sensitive instruments. To investigate this technical possibility, long-term tidal measurements were carried out at the TV tower and at the church Kecske in Sopron (Hungary) by the Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences. The results show that the main diurnal and semidiurnal tidal waves are measurable but sometimes they are strongly disturbed by weather variations (temperature, wind, sunshine). The changes in the response of the object to the periodical tidal exciting signal could give us information about the health of the whole structure of the object. The relationship between the object and the ground deformations can be probably used for earthquake risk assessment of the object.

Published Online: 2007-07-15
Published in Print: 2007-05-23

Copyright 2007, Walter de Gruyter

Downloaded on 19.3.2024 from https://www.degruyter.com/document/doi/10.1515/jag.2007.006/html
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