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.
References
Bischop, P., and Fladwell, G. (1963). “An investigation into the theory of resonance testing.” Philos. Trans. R. Soc. London, 255A(1055), 241–280.
Brincker, R., Zhang, L., and Andersen, P. (2000). “Modal identification from ambient responses using frequency domain decomposition.” Proc., 18th Int. Modal Analysis Conf., Society of Experimental Mechanics, Bethel, Conn., 625–630.
Caetano, E., and Cunha, A. (2004). “Experimental and numerical assessment of the dynamic behaviour of a stress-ribbon footbridge.” Struct. Concr., 5(1), 29–38.
Cunha, A., Caetano, E., Moutinho, C., and Magalhães, F. (2005). “Damping identification in a stress-ribbon footbridge.” Proc., 6th European Conf. on Structural Dynamics: Eurodyn 2005, C. Soize and G. Schuëller, eds., Millpress Science Publishers, Rotterdam, The Netherlands, 243–248.
Deckers, K., Guillaume, P., Lefeber, D., De Roeck, G., and Reynders, E. (2008). “Modal testing of bridges using low-weight pneumatic artificial muscle actuators.” Proc., IMAC 26, the Int. Modal Analysis Conf.
Dougherty, E. (1999). Random processes for image and signal processing, SPIE, Bellingham, Wash.
Ewins, D. J. (2000). Modal testing, 2nd Ed., Research Studies Press, Baldock, U.K.
Guillaume, P., De Troyer, T., Devriendt, C., and De Sitter, G. (2006). “OMAX a combined experimental-operational modal analysis approach.” Proc., ISMA2006 Int. Conf. on Noise and Vibration Engineering, P. Sas and M. De Munck, eds., Katholieke Univ., Leuven, Belgium, 2985–2996.
Han, M. -C., and Wicks, A. (1989). “On the application of forsythe orthogonal polynomials for global modal parameter estimation.” Proc., 7th Int. Modal Analysis Conf., Society of Experimental Mechanics, Bethel, Conn., 625–630.
Heylen, W., Lammens, S., and Sas, P. (1997). Modal analysis theory and testing, Dept. of Mechanical Engineering, Katholieke Universiteit Leuven, Leuven, Belgium.
Juang, J. -N. (1994). Applied system identification, Prentice-Hall, Englewood Cliffs, N.J.
Juang, J. -N., and Pappa, R. S. (1985). “An eigensystem realization algorithm for modal parameter identification and model reduction.” J. Guid. Control Dyn., 8(5), 620–627.
Krämer, C., de Smet, C., and Peeters, B. (1999). “Comparison of ambient and forced vibration testing of civil engineering structures.” Proc., IMAC 17, the Int. Modal Analysis Conf., Society of Experimental Mechanics, Bethel, Conn., 1030–1034.
Maia, N., and Silva, J. (1997). Theoretical and experimental modal analysis, Research Studies Press, Taunton, U.K.
Parloo, E., Cauberghe, B., Benedettini, F., Alaggio, R., and Guillaume, P. (2005). “Sensitivity-based operational mode shape normalization: Application to a bridge.” Mech. Syst. Signal Process., 19(1), 43–55.
Parloo, E., Verboven, P., an Guillaume, P., and Van Overmeire, M. (2002). “Sensitivity-based operational mode shape normalization.” Mech. Syst. Signal Process., 16(5), 757–767.
Peeters, B., and De Roeck, G. (1999). “Reference-based stochastic subspace identification for output-only modal analysis.” Mech. Syst. Signal Process., 13(6), 855–878.
Peeters, B., and De Roeck, G. (2001). “Stochastic system identification for operational modal analysis: A review.” ASME J. Dyn. Syst., Meas., Control, 123(4), 659–667.
Peeters, B., Maeck, J., and De Roeck, G. (2001). “Vibration-based damage detection in civil engineering: Excitation sources and temperature effects.” Smart Mater. Struct., 10(3), 518–527.
Reynders, E., and De Roeck, G. (2008). “Reference-based combined deterministic-stochastic subspace identification for experimental and operational modal analysis.” Mech. Syst. Signal Process., 22(3), 617–637.
Reynders, E., Pintelon, R., and De Roeck, G. (2008). “Uncertainty bounds on modal parameters obtained from stochastic subspace identification.” Mech. Syst. Signal Process., 22(4), 948–969.
Shih, C., Tsuei, Y., Allemang, R., and Brown, D. (1988). “Complex mode indicator function and its applications to spatial domain parameter estimation.” Mech. Syst. Signal Process., 2(4), 367–377.
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© 2010 ASCE.
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Received: May 28, 2008
Accepted: Nov 11, 2009
Published online: May 14, 2010
Published in print: Jun 2010
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