عنوان مقاله [English]
Structural damage detection is one of the primary goals of structural health monitoring. The minimum safety can be provided upon timely identification of the damaged elements and appropriate decisions (repairing or replacing the damaged elements). Today, the use of concrete-filled steel tube composite columns in the construction industry, especially high-rise buildings, is increasing. In these columns, the concrete core debonding from the steel tube is considered a prevalent type of damage. This study discusses the impact of such debonding on dynamic modal properties (natural frequencies and vibration mode shapes) and the detection of debonding damage area based on wavelet analysis. Debonding to a depth of 3 mm was defined reduction in concrete stiffness in connection with the steel tube, and the column was subjected to frequency analysis. Modal information, including frequency values and vibration mode shapes, were extracted. Differences in frequency values and modal assurance criterion (MAC) smaller than one were observed between primary and secondary shapes of vibrational modes due to the presence of debonded areas. The results showed that with the addition of a new debonding damaged area, the rate of reduction of frequency values increases. The damage index was proposed based on the detail coefficients obtained from discrete wavelet analysis of primary and secondary shapes of vibration modes to identify the area of detachment damage. The results showed that the relative minimum and maximum values in the damage index for all modes occurred in debonding damaged areas. Moreover, the damage index values of different damaged areas were independent of each other. Indeed, the damage index values of other debonding damage situations did not change when a new debonding damage area was added. This is a positive point in the damage detection process with multiple debonded areas because in this case, not detecting a debonding damage area can not affect the detection of other debonding damage situations.