Debbonding damage detection in concrete filled tube columns by experimental modal data

CFT column significantly used in tall building and bridges due to high load bearing capacity. Considering the importance and position of these types of columns in structural engineering science and because they are used in specific structures partial damage may result in larger and unrecoverable damage before detection. Accordingly, the basis for the identification of damage in this structural element is more of a researcher's attention. One of the possible damages in these columns is the separation of the steel wall from the concrete core. In this study, the detachment damage was simulated by a thin layer of polystyrene of 6 x 40 cm in one of the columns between the concrete core and the steel wall and modal data of columns have been determined and analyzed. Comparison of frequency, shape of modes, and MAC and COMAC data of healthy and damaged specimen show which occurred in the structure of the damage. In addition, wavelet transform has been used to identify the location of damage. The results of the analysis show that sudden jump occurred in 0.2m and 0.6m in any of the main structures. Which, in the wavelet transform method, indicates discontinuity in the form of the structure's modulus, In this way, the location of the damage is identified with the least possible error.