Damping characteristics of a footbridge: Mysteries and truths

Reto Cantieni; Anela Bajric; Rune Brincker

doi:10.1007/978-3-319-29763-7_27

Damping characteristics of a footbridge: Mysteries and truths

Reto Cantieni, Anela Bajric, Rune Brincker

RCI Dynamics

Research output: Chapter in Book/Report/Conference proceeding › Article in proceedings › Research › peer-review

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Abstract

As a consequence of a paper presented by Michael Mistler at the VDI-Baudynamik-Tagung in Kassel, Germany, in April 2015, the authors checked the damping coefficients having been estimated for a footbridge in autumn 2014. Mistler stated that the critical damping ratio estimated from a halfpower bandwidth procedure to be dependent on frequency resolution for low frequency modes. Based on the data presented here this statement can be confirmed. The dependency on frequency resolution was found to be due to the leakage phenomenon on the spectral density. This fact may have been known in the academic world but not in the world of engineers applying OMA in practice. In this paper it is presented how the leakage on the spectral density estimate is affecting the damping estimation through OMA based frequency domain identification. Finally the paper compares the damping estimated in the time and frequency domain from ambient tests, with the damping estimated from the free decays. Unfortunately, bias error on damping values determined from analyses in the frequency domain is worst on low frequency modes usually being the most important ones when dealing with a resonance problem in practice.

Original language	English
Title of host publication	Dynamics of Coupled Structures : Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016
Editors	Matt Allen, Randall L. Mayes , Daniel Rixen
Volume	4
Publisher	Springer
Publication date	2016
Pages	283-292
Chapter	27
ISBN (Print)	978-3-319-29762-0
ISBN (Electronic)	978-3-319-29763-7
DOIs	https://doi.org/10.1007/978-3-319-29763-7_27
Publication status	Published - 2016
Event	34^th Conference and Exposition on Structural Dynamics of Multiphysical Systems - Rosen Plaza Hotel, Orlando, United States Duration: 25 Jan 2016 → 28 Jan 2016 Conference number: 34 http://eventegg.com/imac-xxxiv/

Conference

Conference	34^th Conference and Exposition on Structural Dynamics of Multiphysical Systems
Number	34
Location	Rosen Plaza Hotel
Country/Territory	United States
City	Orlando
Period	25/01/2016 → 28/01/2016
Internet address	http://eventegg.com/imac-xxxiv/

Series	Conference Proceedings of the Society for Experimental Mechanics Series
ISSN	2191-5644

Keywords

Ambient vibration testing
Enhanced frequency domain decomposition
Free decay process
Half power bandwidth procedure
Ibrahim time domain identification
Structural damping ratio

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10.1007/978-3-319-29763-7_27

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Cantieni, Reto ; Bajric, Anela ; Brincker, Rune. / Damping characteristics of a footbridge: Mysteries and truths. Dynamics of Coupled Structures: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016. editor / Matt Allen ; Randall L. Mayes ; Daniel Rixen . Vol. 4 Springer, 2016. pp. 283-292 (Conference Proceedings of the Society for Experimental Mechanics Series).

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title = "Damping characteristics of a footbridge: Mysteries and truths",

abstract = "As a consequence of a paper presented by Michael Mistler at the VDI-Baudynamik-Tagung in Kassel, Germany, in April 2015, the authors checked the damping coefficients having been estimated for a footbridge in autumn 2014. Mistler stated that the critical damping ratio estimated from a halfpower bandwidth procedure to be dependent on frequency resolution for low frequency modes. Based on the data presented here this statement can be confirmed. The dependency on frequency resolution was found to be due to the leakage phenomenon on the spectral density. This fact may have been known in the academic world but not in the world of engineers applying OMA in practice. In this paper it is presented how the leakage on the spectral density estimate is affecting the damping estimation through OMA based frequency domain identification. Finally the paper compares the damping estimated in the time and frequency domain from ambient tests, with the damping estimated from the free decays. Unfortunately, bias error on damping values determined from analyses in the frequency domain is worst on low frequency modes usually being the most important ones when dealing with a resonance problem in practice.",

keywords = "Ambient vibration testing, Enhanced frequency domain decomposition, Free decay process, Half power bandwidth procedure, Ibrahim time domain identification, Structural damping ratio",

author = "Reto Cantieni and Anela Bajric and Rune Brincker",

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booktitle = "Dynamics of Coupled Structures",

note = "34<sup>th</sup> Conference and Exposition on Structural Dynamics of Multiphysical Systems, IMAC XXXIV ; Conference date: 25-01-2016 Through 28-01-2016",

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Cantieni, R, Bajric, A & Brincker, R 2016, Damping characteristics of a footbridge: Mysteries and truths. in M Allen, RL Mayes & D Rixen (eds), Dynamics of Coupled Structures: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016. vol. 4, Springer, Conference Proceedings of the Society for Experimental Mechanics Series, pp. 283-292, 34^th Conference and Exposition on Structural Dynamics of Multiphysical Systems, Orlando, Florida, United States, 25/01/2016. https://doi.org/10.1007/978-3-319-29763-7_27

Damping characteristics of a footbridge: Mysteries and truths. / Cantieni, Reto; Bajric, Anela; Brincker, Rune.
Dynamics of Coupled Structures: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016. ed. / Matt Allen; Randall L. Mayes ; Daniel Rixen . Vol. 4 Springer, 2016. p. 283-292 (Conference Proceedings of the Society for Experimental Mechanics Series).

Research output: Chapter in Book/Report/Conference proceeding › Article in proceedings › Research › peer-review

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AU - Bajric, Anela

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N2 - As a consequence of a paper presented by Michael Mistler at the VDI-Baudynamik-Tagung in Kassel, Germany, in April 2015, the authors checked the damping coefficients having been estimated for a footbridge in autumn 2014. Mistler stated that the critical damping ratio estimated from a halfpower bandwidth procedure to be dependent on frequency resolution for low frequency modes. Based on the data presented here this statement can be confirmed. The dependency on frequency resolution was found to be due to the leakage phenomenon on the spectral density. This fact may have been known in the academic world but not in the world of engineers applying OMA in practice. In this paper it is presented how the leakage on the spectral density estimate is affecting the damping estimation through OMA based frequency domain identification. Finally the paper compares the damping estimated in the time and frequency domain from ambient tests, with the damping estimated from the free decays. Unfortunately, bias error on damping values determined from analyses in the frequency domain is worst on low frequency modes usually being the most important ones when dealing with a resonance problem in practice.

AB - As a consequence of a paper presented by Michael Mistler at the VDI-Baudynamik-Tagung in Kassel, Germany, in April 2015, the authors checked the damping coefficients having been estimated for a footbridge in autumn 2014. Mistler stated that the critical damping ratio estimated from a halfpower bandwidth procedure to be dependent on frequency resolution for low frequency modes. Based on the data presented here this statement can be confirmed. The dependency on frequency resolution was found to be due to the leakage phenomenon on the spectral density. This fact may have been known in the academic world but not in the world of engineers applying OMA in practice. In this paper it is presented how the leakage on the spectral density estimate is affecting the damping estimation through OMA based frequency domain identification. Finally the paper compares the damping estimated in the time and frequency domain from ambient tests, with the damping estimated from the free decays. Unfortunately, bias error on damping values determined from analyses in the frequency domain is worst on low frequency modes usually being the most important ones when dealing with a resonance problem in practice.

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KW - Enhanced frequency domain decomposition

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KW - Half power bandwidth procedure

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KW - Structural damping ratio

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SN - 978-3-319-29762-0

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T3 - Conference Proceedings of the Society for Experimental Mechanics Series

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BT - Dynamics of Coupled Structures

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A2 - Mayes , Randall L.

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PB - Springer

T2 - 34<sup>th</sup> Conference and Exposition on Structural Dynamics of Multiphysical Systems

Y2 - 25 January 2016 through 28 January 2016

ER -

Cantieni R, Bajric A, Brincker R. Damping characteristics of a footbridge: Mysteries and truths. In Allen M, Mayes RL, Rixen D, editors, Dynamics of Coupled Structures: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016. Vol. 4. Springer. 2016. p. 283-292. (Conference Proceedings of the Society for Experimental Mechanics Series). doi: 10.1007/978-3-319-29763-7_27

Damping characteristics of a footbridge: Mysteries and truths

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