Estimation of modal parameters for structurally damped systems using wavelet transform

• A method is proposed to identify the modal parameters of a structurally damped system.
• The Morlet wavelet is used to determine the natural frequencies and damping ratios.
• A method is presented for identification of mode shapes.

In this paper, a procedure is presented to determine the modal parameters of a system with proportional structural damping exited by an impact force. A Morlet wavelet transform with an adjusting parameter is used to estimate the natural frequencies and damping factors from free-decay responses of structure. Also a method is used for identification of mode shapes from the estimated natural frequencies of wavelet transform and the free responses of structure. It is shown that the mode shape identification method can average the data in the noisy environments and reduce the effect of noise. A numerical example as well as two experimental case studies on a beam and a trapezoidal concrete plate demonstrates the validity of method.