Improving the Fatigue Life of Large Offshore Foundations

Morten Kristiansen*, Radoslav Darula, Benny Endelt, Anders Faarbæk Mikkelstrup, Jan Schjødt-Thomsen, Jens Henrik Andreasen, Farhang Farrokhi, Poul Kyvsgaard Hansen, Per Baunegaard With Jensen, Eric Putnam, Nis Hansen

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Offshore foundations are subject to fatigue due to wind and wave loads during their lifetime. Post-weld treatment is a group of techniques well known to improve the fatigue life. This study investigates how this is applicable for large structures, i.e. a 2.4 meter jacket T-node. A large scale empirical study was performed and results were obtained from a SN-diagram based on three repetitions and supported by a theoretical background. The as welded samples performed as expected and on the safe side of the category 56 line. Unexpectedly, the burr grinded samples showed no improvement and had an evidently larger variance. Both ultrasonic impact treatment and especially pneumatic impact treatment showed improvements, but did not reach the expected category 125 line. The results were substantiated with strain-gauge measurements for hot spot analysis. The obtained results on fatigue life improvements give rise to apply post weld treatment in an industrial scale for offshore construction. However, it also brings up the discussion of the necessity to redesign structures in order to automate the treatment in a cost efficient manner.
Original languageEnglish
Article number103314
JournalMarine Structures
Volume87
ISSN0951-8339
DOIs
Publication statusPublished - Jan 2023

Keywords

  • Burr grinding
  • Fatigue
  • Pneumatic impact treatment
  • Post weld treatment
  • Ultrasonic impact treatment

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