| 摘要 |
PROBLEM TO BE SOLVED: To diagnose a large-sized concrete structure in a short time even when a scaffold is not available. SOLUTION: A pulse laser beam 7 is emitted toward a surface 2 of a diagnosed portion 4 in concrete structure 1 to generate an elastic wave 10 by thermal expansion. A surface wave 9 and the elastic wave 10 in the irradiation are detected with the lapse of time by a laser interferometer 8 for collimating the surface 2 of the diagnosed portion 4, the presence of an internal defect 5 or a buried body in the concrete structure 1 in the diagnosed portion 4 is diagnosed based on a waveform change from detection of the surface wave 9 to detection of the final elastic wave 10. Preferably, a depth di from the surface 2 to the internal defect 5 or the buried body in the diagnosed portion 4 is calculated based on a concrete elastic characteristic v of the diagnosed portion 4 and a time ti from the detection of the surface wave 9 to the detection of the each elastic wave 10i. The concrete elastic characteristic v and concrete strength of the diagnosed portion 4 are found based on a time max from the detection of the surface wave 9 to the detection of the final elastic wave 10 and a concrete thickness w of the diagnosed portion 4, when the concrete thickness w is known.
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