Structual Damage Identification Methods Based On Normalized Frequency Change Ratio And The Index Of Flexibility

As research hotspot of engineering science in recent years, structural damage identification mainly detects the dynamic characteristics of the objective structure, and the obtained data is analyzed. The damage condition of the structure is defined based on the analysis on the data. There are three key issues in the damage identification. (1) whether the structural damage exists; (2) the location of the damage should be determined; (3) how to determine the extent and type of the damage.In this paper, several indicators of structural damages were studied under the integration of principles and experiments. The main contents and innovations are as follows:1. With the method of wavelet transform, the time-domain signal can be de-noised and filtered. We employed the wavelet transform to eliminate the signal noise and interference in the process of structural dynamic test. With the preprocessing of wavelet transform, the vibration signal would have a higher signal-to-noise ratio. And the dynamic parameters of the structure could be captured more accurately. Thus, the structural damage can be indentified effectively.2. We analyzed the damage identification theory based on frequency change, and proposed an improved damage identification theory on the basis of the normalized frequency change ratio in order to improve the deficiencies in the damage identification. Furthermore, with the ANASYS simulation and experiments to the cantilever beam, we analyzed the efficiency and accuracy of the improved theory. The results show that the improved theory is a kind of damage identification indicator which is sensitive to structural damage, and it could identify the structural damage effectively and accurately.3. Flexibility matrix is one of the common detection parameters in the structural damage of framework. However, there are many indicators based on the flexibility matrix. In this paper, we selected three indicators: flexibility deviation? , the flexibility curvature? and flexibility curvature deviationδ_FCD. We discussed and analyzed the three theories on details, and studied the accuracy and practicability of each indicator for the damage location identification. With the comparison of the numerical simulation and experimental results of the framework, we analyzed accuracy and practicability of the three kinds of indicators. And the results indicated that the flexibility curvature is the most accurate and practical indicator in structural damage identification.