Identification of friction-coupled offshore platforms by output-only method

Tobias Friis, Karsten K. Vesterholm, Evangelos I. Katsanos, Anders Brandt, Rune Brincker

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


A structural health monitoring (SHM) program can improve the structural integrity of offshore structures, however, the SHM scheme implies extraction of linear time-invariant modal parameters by Operational Modal Analysis (OMA). Inherently, the offshore platforms are nonlinear, and in many cases, the dynamics of the platforms are involving a friction-induced coupling that stems from bearings in the bridges connecting the platforms. This mechanism is causing the platforms to interchange between acting either as one system or separate systems, depending on the sliding or sticking state of the bearings. Along these lines, the present paper proposes an identification framework employing nonlinearity optimised random decrement (NORD) and OMA parameter estimation methods to identify two sets of underlying linear modes, relative to the state of the friction-induced coupling, both from the same measurement record.

Original languageEnglish
Title of host publicationThe 29th International Ocean and Polar Engineering Conference
EditorsJin S. Chung, Odd M. Akselsen, HyunWoo Jin, Hiroyasu Kawai, Yongwon Lee, Dmitri Matskevitch, Suak Ho Van, Decheng Wan, Alan M. Wang, Satoru Yamaguchi
Number of pages6
PublisherInternational Society of Offshore & Polar Engineers
Publication date2019
ISBN (Print)9781880653852
Publication statusPublished - 2019
EventThe 29th International Ocean and Polar Engineering Conference - Honolulu, United States
Duration: 16. Jun 201921. Jun 2019
Conference number: 29


ConferenceThe 29th International Ocean and Polar Engineering Conference
Country/TerritoryUnited States
SeriesProceedings of the International Offshore and Polar Engineering Conference


  • Operational Modal Analysis
  • Response dependent identification
  • friction-coupled systems
  • nonlinear dynamics
  • random decrement technique
  • nonlinearity optimised random decrement
  • NORD


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