Journal Published Online: 01 September 2003
Volume 26, Issue 3

Resonant Column Testing: The Inherent Counter EMF Effect



The standard magnet-coil driving system in resonant column devices provides the required cyclic excitation; however, it inherently produces a counter electromotive force that opposes the motion. In this study, the resonant column is modeled as an electro-mechanical system to quantitatively examine the counter electromotive effect and to explore its effect on resonant frequency and damping ratio computed from voltage-based measurements. The model is verified with two independent sets of experiments. Experimental and analytical results show that the measurement bias is more pronounced on the damping ratio than on the resonant frequency, the damping bias is not a device constant but varies with frequency, and the error is particularly relevant in low-loss and low-stiffness specimens (such as dry sands at low confinement). The electro-mechanical model permits developing device-specific correction charts that can be used to reexamine previously published damping ratio data gathered with voltage-based resonant column procedures.

Author Information

Wang, Y-H
Civil Engineering, Hong Kong University of Science and Technology, Hong Kong
Cascante, G
Civil Engineering, University of Waterloo, Waterloo, Canada
Santamarina, JC
Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA
Pages: 11
Price: $25.00
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Stock #: GTJ11305J
ISSN: 0149-6115
DOI: 10.1520/GTJ11305J