Analytic wavelet transformation‐based modal parameter identification from ambient responses

Analytic wavelet transform (AWT) based on Gabor wavelet function overcomes the deficiency of the time-domain localization of traditional Fourier transform and the limitation of the constant resolution in the time-frequency domain of short-time Fourier transform. The identification of modal parameters of structures may be carried out by both the amplitude and phase frequency information revealed by resorting to matching mechanism between the wavelet function and complex-valued signal. By applying the AWT in conjunction with the well-known random decrement technique, this paper analyses the time-frequency resolution of Gabor wavelet and the process of identifying structural modal parameters. The method of selecting the parameters of Gabor wavelet function and the formula determining the usable lengths of signal are thus proposed. Eventually, the efficiency of the present method is confirmed by applying it to a numerical simulation data without and with noise contamination of a three degree-of-freedom (3DOF) structure with the closely spaced natural frequencies and to ambient vibration full-scale measurements of a super high-rise building—Shanghai Jin Mao Building excited by wind. Copyright © 2010 John Wiley & Sons, Ltd.