Modal Identification of an Arch Dam Using Combined Frequency Domain Decomposition and Wavelet Transform Method

Operational modal analysis is used to extract the modal parameters of the system based on the responses of the system. Due to the complexity of dam-foundation-reservoir system, accurate measurement of the input excitation to the dam body in not possible. Therefore, in the operational modal analysis methods, the dynamic properties of the system are identified only based on the responses of the system [1]. In classical system identification methods, the structure vibrates due to an external force which may cause it to be out of operation during tests. In addition, the forced vibration tests put the structure in danger of possible damage [2]. Utilizing of ambient vibrations to obtain modal parameters of the system is one of the most important advantages of the operational modal analysis in comparison with classical methods. Low amplitude and low signal to noise ratio of ambient vibration can cause inaccuracy and uncertainty in the identified modal characteristics therefore several signal processing methods should be used to increase the accuracy of the results.