Damping ratio estimation using hybrid methods

Abstract

Much effort has been expended in attempts to estimate dynamic response parameters of structures. Damping ratios have been estimated with varying degrees of success. Some of this effort has been motivated by active research and development of structural integrity monitoring systems, for design purposes, accurate estimates of damping ratios are important. In this work we apply several modern spectral analysis methods (maximum likelihood method, maximum entropy method and the Lagunas-Hernandez method) plus the spectral moment relations near natural frequency to the estimation of damping ratios. We use simulated vibration data and test the different choices of the spectral method in order to obtain the best estimation procedure. The spectral shape of the response near the natural frequency is estimated first as the basis for further analysis. Half-power bandwidth and spectral moments are then derived from the spectral shape. The bandwidth and moments are subsequently related to the damping ratio. An iterated method for obtaining the damping ratio from the spectral moments has been proposed by Shyam Sunder. The half-power bandwidth and moments are crucial to this method as is the estimation of the spectral shape, there are many methods available to estimate spectral shape. Different combinations of the two methods gives varied damping ratios, in this work we try to identify the best combinations. We have used many sets of exact and simulated data and applies many different combinations. Results show that the maximum entropy spectral method and the method of Shyam Sunder is the best combination from our tests.