Use of Instantaneous Estimators for the Evaluation of Structural Damping

This study focuses on the definition of time–frequency instantaneous estimators to be employed in the identification of structural damping from signals measured in ambient vibration conditions. The estimators discussed here are obtained from instantaneous curve fitting applied directly to time–frequency representations of dynamicresponse signals. One of the strong points of this technique is its flexibility: from each signal, a time function of modal damping and amplitude is extracted, providing punctual information on the stability and consistency of damping estimate. The aim of this paper is to study the implications related to the use of this method with linear time–frequency representations. Linear representations, within the inherent limits of their linear nature, still retain attractive computational advantages and lend themselves to a clear theoretical interpretation. In the last part of the paper, a series of numerical applications to simple systems is presented to support theoretical argumentations. Finally, an experimental application to the identification of the damping in a real concrete building is shown. r 2003 Elsevier Ltd. All rights reserved.