Damage Detection in Concrete Filled Tube Columns Based on Experimental Modal Data and Wavelet Technique

Damage detection in Concrete-Filled Tubes (CFSTs) and the study of their application in special structures such as high-rise buildings, towers and bridges are important issues. CFST columns are widely studied by researchers and engineers due to the simultaneous utilization of both their steel and concrete properties. Hence, any damage to this structural element may result in extremely severe and irreversible injury. In this study, we researched the factors that may be involved in such damage. In addition, identification of a particular type of damage that may be due to the buckling of steel tube plates was performed in this study as well. Since, the buckled part in the column is eliminated from the system or decreases its bearing capacity significantly, in this study, in order to simulate the damage, a part of the CFST column steel wall was cut off and eliminated. And, since buckling is more likely to occur in the middle of the column, damage has been located in the middle of the column. After preparing the specimen and performing the tests, the modal data was extracted and was entered in the MATLAB software to be analyzed with the aid of the wavelet transform tool. The results showed that the frequency was reduced and the mode shape of the specimens did not match entirely before and after the damage with the Modal Assurance Criteria (MAC), which indicated damage in a specimen. To identify the location of the damage, the mode shape obtained from the experimental modal was given to the wavelet transform as the input signal and Daubechies (Db) wavelet was applied to correctly identify the location of the damage.