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Influence of impact source frequency on impact-echo data from testing of concrete structures
Impact-echo non-destructive testing was applied on site to investigate a post-tensioned concrete bridge beam. Element thickness information and position of ducts was successfully obtained from the data. Nevertheless, the observation of the recorded signals indicated that for an unequivocal data interpretation, it is particularly important the range of the excited frequencies. The frequency range can be described via two parameters: centre and maximum frequency. In particular the centre frequency of the wave has a particular significance as, in the proximity of this value, the wave components have maximal amplitudes and the frequency peak amplitude is an important evaluation criterion for interpretation of measured data. Therefore, the wave centre frequency should be excited in the range of the expected measured frequency and, anyway, the maximum input frequency should be higher than the expected measured frequency. Then, it would be ensured that sufficiently large amplitude frequency components are excited in the frequency range of interest and the successful identification of the relevant frequency peaks would be guaranteed. This would positively affect the quality of the data and ease data interpretation in the case of complex structures. Preliminary results from calibration studies with steel spheres used as wave impact source showed how strongly the centre frequency could be affected by the size of the sphere and the values obtained are of particular interest for a correct planning of impact-echo measurements. In particular, values of contact time, centre and maximum frequency could be extrapolated from the measurements for different sphere sizes. A practical consequence of the knowledge of these values is that the impact source may be properly selected, depending on the aims of the test and the geometry of the concrete structure. Further research studies are planned, including the investigation of the dependencies of input frequency from impact strengh.
Influence of impact source frequency on impact-echo data from testing of concrete structures
Impact-echo non-destructive testing was applied on site to investigate a post-tensioned concrete bridge beam. Element thickness information and position of ducts was successfully obtained from the data. Nevertheless, the observation of the recorded signals indicated that for an unequivocal data interpretation, it is particularly important the range of the excited frequencies. The frequency range can be described via two parameters: centre and maximum frequency. In particular the centre frequency of the wave has a particular significance as, in the proximity of this value, the wave components have maximal amplitudes and the frequency peak amplitude is an important evaluation criterion for interpretation of measured data. Therefore, the wave centre frequency should be excited in the range of the expected measured frequency and, anyway, the maximum input frequency should be higher than the expected measured frequency. Then, it would be ensured that sufficiently large amplitude frequency components are excited in the frequency range of interest and the successful identification of the relevant frequency peaks would be guaranteed. This would positively affect the quality of the data and ease data interpretation in the case of complex structures. Preliminary results from calibration studies with steel spheres used as wave impact source showed how strongly the centre frequency could be affected by the size of the sphere and the values obtained are of particular interest for a correct planning of impact-echo measurements. In particular, values of contact time, centre and maximum frequency could be extrapolated from the measurements for different sphere sizes. A practical consequence of the knowledge of these values is that the impact source may be properly selected, depending on the aims of the test and the geometry of the concrete structure. Further research studies are planned, including the investigation of the dependencies of input frequency from impact strengh.
Influence of impact source frequency on impact-echo data from testing of concrete structures
Einfluss von Schlagquellenfrequenz auf Impakt-Echo-Daten bei der Untersuchung von Betonstrukturen
Lausch, R. (author) / Knapp, J. (author) / Colla, C. (author)
2001
12 Seiten, 15 Bilder, 1 Tabelle, 9 Quellen
(Nicht paginiert).
Conference paper
English
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