Natural frequencies and dampings identification using wavelet transform: application to real data

The wavelet transform is used as a time-frequency representation for system identification purposes. It is shown that wavelet analysis of the free response of a system allows the estimation of the natural frequencies and viscous damping ratios. The advantages of the wavelet transform in the analysis of the free decay of the system are underlined and a comparison with previous techniques is made. The accuracy of this method is confirmed by applying it to a numerical example and the acceleration responses from a real bridge under ambient excitations (the Queensborough Bridge in Vancouver, Canada). The results obtained agree with those previously obtained on the dynamic behaviour of the Queensborough Bridge.