Nondestructive evaluation of concrete quality and integrity in composite columns

This paper summarizes the results obtained from the studies aimed at determining the feasibility of using the impact-echo technique for nondestructive evaluation of concrete quality and integrity in composite columns. Both numerical and experimental studies are carried out to gain a thorough understanding of the transient impact response of composite columns with/without flaws. Results obtained from these studies show that the impact response of a solid composite column is composed of a number of cross-sectional modes of vibration generated by multiple wave reflections between close proximity of boundaries. The frequency of the fundamental mode can be used to determine the P-wave speed in concrete. The presence of flaws disrupts the spectral pattern associated with the solid case. A shift of the fundamental frequency to a lower value is the key to identifying the presence of a flaw. In addition, the spectrum will also show a high amplitude peak at the frequency corresponding to the depth of the flaw. (C) 1999 Elsevier Science Ltd. All rights reserved