Comparison of Modal Parameters Estimated from Operational and Experimental Modal Analysis Approaches

Abstract

Experimental modal testing has been performed for several decades as an approach to identify system characteristics. This involves a controlled test where the applied force and response are measured to identify frequency response functions which are processed to obtain modal parameters. More recently there has been a trend to utilize output only measurement approaches to extract similar information. The main advantage is that the structure need not be brought to the test lab and operating responses can be used to extract similar modal parameters. However, the operating approaches may not always obtain the same modes as those obtained from the traditional modal test.

This paper presents a study of the modal parameters obtained from both traditional modal testing and operational modal analysis approaches to compare the two sets of estimated parameters. Data from several structures are compared to show the differences between the two approaches.