Estimation of modal parameters confidence intervals: A simple numerical example

Abstract

Structural dynamic testing is concerned with estimation of system properties i.e. modal parameters. Modal parameters are extracted from measured data that are subjected to variability. Therefore these parameters when extracted from different data samples can be assumed to be random variables, which can be represented in terms of mean and standard deviation. These levels of variability can be quite important in areas of study such as damage identification given the relative insensitivity of the modal parameters to many types of system damage. This work aims at investigating how two different statistical techniques can estimate the confidence intervals on global modal parameters (natural frequencies and damping ratios), estimated by two different methods of modal extraction, on simulated data (corrupted by different levels of noise). Bootstrap and jackknifing techniques will be used on both time (LSCE) and frequency (UMPA) domain SIMO estimators. This will lead to a comparison of the capabilities of each technique to estimate the statistical properties of the modal parameters. Finally ongoing works on local modal parameters (i.e. mode shapes) estimation will be presented through the use of virtual FRFs constructed from surrogate modeling of the FRFs sets. © The Society for Experimental Mechanics, Inc. 2013.