Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment

James Brownjohn; Alison Raby; Siu Kui Au; Zuo Zhu; Xinrui Wang; Alessandro Antonini

Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment

James Brownjohn, Alison Raby, Siu Kui Au, Zuo Zhu, Xinrui Wang, Alessandro Antonini

Coastal Engineering

Research output: Chapter in Book/Conference proceedings/Edited volume › Conference contribution › Scientific › peer-review

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Abstract

A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.

Original language	English
Title of host publication	8th IOMAC - International Operational Modal Analysis Conference, Proceedings
Subtitle of host publication	13-15 May, Copenhagen, Denmark
Editors	Sandro D. R. Amador, Rune Brincker, Evangelos I. Katsanos, Manuel Lopez Aenlle, Pelayo Fernandez
Publisher	International Operational Modal Analysis Conference (IOMAC)
Pages	9-16
Number of pages	8
ISBN (Electronic)	9788409049004
Publication status	Published - 2019
Event	8th International Operational Modal Analysis Conference, IOMAC 2019 - Copengahen, Denmark Duration: 13 May 2019 → 15 May 2019

Conference

Conference	8th International Operational Modal Analysis Conference, IOMAC 2019
Country/Territory	Denmark
City	Copengahen
Period	13/05/19 → 15/05/19

Bibliographical note

Accepted Author Manuscript

Keywords

Assessment
Bayesian
Condition
Identification
Lighthouse
OMA
System

Access to Document

AntoniniIOMAC2019Accepted author manuscript, 2.03 MB

Cite this

Brownjohn, J., Raby, A., Au, S. K., Zhu, Z., Wang, X., & Antonini, A. (2019). Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment. In S. D. R. Amador, R. Brincker, E. I. Katsanos, M. Lopez Aenlle, & P. Fernandez (Eds.), 8th IOMAC - International Operational Modal Analysis Conference, Proceedings: 13-15 May, Copenhagen, Denmark (pp. 9-16). International Operational Modal Analysis Conference (IOMAC).

Brownjohn, James ; Raby, Alison ; Au, Siu Kui et al. / Bayesian oma of offshore rock lighthouses : Surprises with close modes, symmetry and alignment. 8th IOMAC - International Operational Modal Analysis Conference, Proceedings: 13-15 May, Copenhagen, Denmark . editor / Sandro D. R. Amador ; Rune Brincker ; Evangelos I. Katsanos ; Manuel Lopez Aenlle ; Pelayo Fernandez. International Operational Modal Analysis Conference (IOMAC), 2019. pp. 9-16

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title = "Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment",

abstract = "A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.",

keywords = "Assessment, Bayesian, Condition, Identification, Lighthouse, OMA, System",

author = "James Brownjohn and Alison Raby and Au, {Siu Kui} and Zuo Zhu and Xinrui Wang and Alessandro Antonini",

note = "Accepted Author Manuscript; 8th International Operational Modal Analysis Conference, IOMAC 2019 ; Conference date: 13-05-2019 Through 15-05-2019",

year = "2019",

language = "English",

pages = "9--16",

editor = "Amador, {Sandro D. R.} and Rune Brincker and Katsanos, {Evangelos I.} and {Lopez Aenlle}, Manuel and Pelayo Fernandez",

booktitle = "8th IOMAC - International Operational Modal Analysis Conference, Proceedings",

publisher = "International Operational Modal Analysis Conference (IOMAC)",

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Brownjohn, J, Raby, A, Au, SK, Zhu, Z, Wang, X & Antonini, A 2019, Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment. in SDR Amador, R Brincker, EI Katsanos, M Lopez Aenlle & P Fernandez (eds), 8th IOMAC - International Operational Modal Analysis Conference, Proceedings: 13-15 May, Copenhagen, Denmark . International Operational Modal Analysis Conference (IOMAC), pp. 9-16, 8th International Operational Modal Analysis Conference, IOMAC 2019, Copengahen, Denmark, 13/05/19.

Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment. / Brownjohn, James; Raby, Alison; Au, Siu Kui et al.
8th IOMAC - International Operational Modal Analysis Conference, Proceedings: 13-15 May, Copenhagen, Denmark . ed. / Sandro D. R. Amador; Rune Brincker; Evangelos I. Katsanos; Manuel Lopez Aenlle; Pelayo Fernandez. International Operational Modal Analysis Conference (IOMAC), 2019. p. 9-16.

Research output: Chapter in Book/Conference proceedings/Edited volume › Conference contribution › Scientific › peer-review

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T1 - Bayesian oma of offshore rock lighthouses

T2 - 8th International Operational Modal Analysis Conference, IOMAC 2019

AU - Brownjohn, James

AU - Raby, Alison

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AU - Wang, Xinrui

AU - Antonini, Alessandro

N1 - Accepted Author Manuscript

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Y1 - 2019

N2 - A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.

AB - A set of seven rock lighthouses around the British Isles was studied by a combination of forced and ambient vibration tests executed with some extreme logistical constraints. Forced vibration testing of the circular section masonry towers combined with experimental modal analysis identified modes with alignment assumed the same as the shaker as well as some interesting effects of helideck retrofit, whereas operational modal analysis revealed the considerable degree of uncertainty in mode shape alignment. Hence Bayesian operational modal analysis was used to characterise the uncertainty and find the best representation of mode shape direction. While perfectly axisymmetric towers would show a single frequency omnidirectional mode, OMA reveals the split modes and allows un unbiased view of directionality. The variability and uncertainty of these mode shape directions are further revealed using Bayesian OMA.

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KW - Condition

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A2 - Katsanos, Evangelos I.

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Brownjohn J, Raby A, Au SK, Zhu Z, Wang X, Antonini A. Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment. In Amador SDR, Brincker R, Katsanos EI, Lopez Aenlle M, Fernandez P, editors, 8th IOMAC - International Operational Modal Analysis Conference, Proceedings: 13-15 May, Copenhagen, Denmark . International Operational Modal Analysis Conference (IOMAC). 2019. p. 9-16

Bayesian oma of offshore rock lighthouses: Surprises with close modes, symmetry and alignment

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Conference

Bibliographical note

Keywords

Access to Document

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