Abstract
In order to rationalize the hammering test and to eliminate the dangerous works for inspecting in concrete structures, an application of remote measurement by the laser doppler vibrometer (LDV) is investigated. The relationship between impact echo and surface vibration of structures measured by LDV is clarified. For a concrete specimen with a void, energy ratio of the power spectrum density is employed to extract local frequencies at void parts, and their location is identified from mode shapes at the frequencies. The identification method is based on the frequency domain analysis of measured surface vibrations. Furthermore, a non-contact input excitation method using sound pressure is also proposed. These results indicate that the LDV has potential applicability to defect identification of concrete structures.
