Experimental evaluation of damping in beams using the acceleration generalized coordinates: A comparison of the FDD and PCA methods

Abstract

The correct evaluation of damping from experimental measurements is important for subsequent analyses, be it in the field of structural dynamics, earthquake engineering, vibration control, structural health monitoring, etc. In this work, we demonstrate how an accurate evaluation of modal damping is possible by using a minimal amount of acceleration sensors and exciting the structure using a simple hammer. However, the transient signals thus recovered must be carefully processed so as to extract as much accuracy from these measurements as possible. The particular experiment used here involved a metallic bridge span, which was simply supported and used for testing moving loads. Both Frequency Domain Decomposition and Principal Component Analysis were employed and subsequently compared, with the latter method showing a clear separation of modes. Thus, an accurate estimation of modal damping values from the free vibration regime is possible using the logarithmic decrement method.