Journal of Ocean Engineering and Technology (한국해양공학회지)

Korean Society of Ocean Engineers (한국해양공학회)
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Out-Of-Plane Bending Stiffnesses in Offshore Mooring Chain Links Based on Conventional and Advanced Numerical Simulation Techniques

기존/개선 수치 해석 기법을 이용한 계류 체인 링크의 면외 굽힘 강성

  • Choung, Joonmo (Department of Naval Architecture and Ocean Engineering, Inha University) ;
  • Lee, Jae-bin (Department of Naval Architecture and Ocean Engineering, Inha University) ;
  • Kim, Young Hun (Department of Naval Architecture and Ocean System Engineering, Kyungnam University)
  • 정준모 (인하대학교 조선해양공학과) ;
  • 이재빈 (인하대학교 조선해양공학과) ;
  • 김영훈 (경남대학교 조선해양시스템공학과)
  • Received : 2018.06.13
  • Accepted : 2018.10.18
  • Published : 2018.10.31
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Abstract

After an accident involving mooring link failures in an offloading buoy, verification of the fatigue safety in terms of the out-of-plane bending (OPB) and in-plane bending (IPB) moments has become a key engineering item in the design of various floating offshore units. The mooring links for an 8 MW floating offshore wind turbine were selected for this study. To identify the OPB stiffness (OPB moment versus interlink angle), a numerical simulation model, called the 3-link model, is usually composed of three successive chain links closest to the fairlead or chain hawse. This paper introduces two numerical simulation techniques for the 3-link analyses. The conventional and advanced approaches are both based on the prescribed rotation approach (PRA) and direct tension approach (DTA). Comparisons of the nominal stress distributions, OPB stiffnesses, hotspot stress curves, and stress concentration curves are presented. The multiple link analyses used to identify the tension angle versus interlink angle require the OPB stiffness data from the 3-link analyses. A convergence study was conducted to determine the minimum number of links for a multi-link analysis. It was proven that 10 links were sufficient for the multi-link analysis. The tension angle versus interlink angle relations are presented based on multi-link analyses with 10 links. It was found that the subsequent results varied significantly according to the 3-link analysis techniques.

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References

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