Combined Experimental-Operational Modal Testing of Footbridges
Publication: Journal of Engineering Mechanics
Volume 136, Issue 6
Abstract
In combined vibration testing, an artificial, measured force is used in operational conditions. This requires the identification of a system model that takes both the measured and the operational excitation into account. Advantages with respect to the classical operational modal analysis approach are the possibility of obtaining mass-normalized mode shapes and the increase of the excitation level and its frequency content. An advantage with respect to the classical experimental modal analysis approach, where the ambient excitation is not modeled, but considered as disturbing noise, is the possibility of using excitation levels that are of the same amplitude, or even smaller, than the ambient excitation levels. In this paper, combined modal testing of footbridges is explored using two case studies: a steel arch footbridge with spans of 75.2 m and 30.3 m and a concrete stress-ribbon footbridge with spans of 30 m and 28 m. The comparison of the modal parameters (eigenfrequencies, damping ratios, mode shapes, and modal scaling factors) obtained from a combined vibration test with the ones obtained from other modal tests and from a finite-element model, demonstrates the feasibility of using small and practical excitation devices for the modal testing of footbridges.
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Acknowledgments
The Wetteren footbridge tests were performed in a joint measurement campaign of the Structural Mechanics Division of K.U. Leuven, Belgium, the Industrial Engineering Department of Katholieke Hogeschool Sint-Lieven in Ghent, Belgium, and the Acoustics and Vibration Research Group from Vrije Universiteit Brussel, Belgium. The writers acknowledge the financial support by the Research Foundation-Flanders (F.W.O.), Belgium and the Research Fund K.U. Leuven, Belgium.
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Information & Authors
Information
Published In
Journal of Engineering Mechanics
Volume 136 • Issue 6 • June 2010
Pages: 687 - 696
Copyright
© 2010 ASCE.
History
Received: May 28, 2008
Accepted: Nov 11, 2009
Published online: May 14, 2010
Published in print: Jun 2010
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