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

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientificpeer-review

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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 languageEnglish
Title of host publication8th IOMAC - International Operational Modal Analysis Conference, Proceedings
Subtitle of host publication13-15 May, Copenhagen, Denmark
EditorsSandro D. R. Amador, Rune Brincker, Evangelos I. Katsanos, Manuel Lopez Aenlle, Pelayo Fernandez
PublisherInternational Operational Modal Analysis Conference (IOMAC)
Number of pages8
ISBN (Electronic)9788409049004
Publication statusPublished - 2019
Event8th International Operational Modal Analysis Conference, IOMAC 2019 - Copengahen, Denmark
Duration: 13 May 201915 May 2019


Conference8th International Operational Modal Analysis Conference, IOMAC 2019

Bibliographical note

Accepted Author Manuscript


  • Assessment
  • Bayesian
  • Condition
  • Identification
  • Lighthouse
  • OMA
  • System


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