Time-frequency domain decomposition for modal identification using ambient excitation tests

Time-frequency technique has been applied in modal identification since the end of the 90s. The modal parameters, i.e, frequencies, damping ratios and mode shapes are often extracted by the use of time-frequency techniques based on free decay response. From ambient excitation tests, the free decay response can be obtained by the random decrement technique. Recently, Le and Paultre have proposed to use correlation function of recorded signal of ambient excitation tests to avoid the random decrement technique as a preprocessing step. They also showed that, using correlation function, the time-frequency technique based on continuous wavelet transform gives good results for modal identification and makes the computation more efficient. In this study, the extension of this technique is proposed in order to give a consistent procedure. The redundant information is removed using singular value decomposition. Numerical examples and results obtained from tests performed on a 3-dimensional truss structure are used to validate the method.