ABSTRACT

A new statistical identification method for modal parameters of bridges using structural ambient vibration responses is presented. The method is composed of improved random decrement technique, wavelet transform and bootstrap method. The improved random decrement technique can be used to deal with zero-mean non-stationary ambient vibration signals directly. The wavelet transform is applied to decouple dense frequency and low damping system because of its advantages in time-frequency domain. The bootstrap procedure is employed to evaluate and decrease the uncertainty of the identification results. The reliability of the proposed method has been validated by a four-degree-of-freedom numerical example. Then, modal parameters of bridges under ambient excitation are estimated using the presented method. The identification accuracy of the method is higher than the traditional time-domain method and the wavelet transform only method, especially for structural damping ratios. The precise identified results can be used to be the foundation of structural health monitoring during the operational phase.