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Bending Behavior of the Mooring Chain Links Subjected to High Tensile Forces

강한 인장 상태에서의 계류 체인 링크의 휨 거동

  • Kim, Seungjun (Dept of Construction Safety and Disaster Prevention Engineering, Daejeon University) ;
  • Won, Deok-Hee (Coastal Development & Ocean Energy Research Division Korea Institute of Ocean Science and Technology)
  • 김승준 (대전대학교, 건설안전방재공학과) ;
  • 원덕희 (한국해양과학기술원, 연안방재연구센터)
  • Received : 2016.06.30
  • Accepted : 2016.10.25
  • Published : 2017.04.27

Abstract

This paper presents the study of the bending behavior of mooring chain links for keeping the position of the offshore floating structures. In general, chain links have been thought as the axial members due to the fundamental boundary condition. But, the flexural stiffness can be induced to the contact surface between chain links when friction occurs at the surface of the chain links due to high tensile force. Especially, the mooring chains for offshore floating platforms are highly tensioned. If the floater suffers rotational motion and the mooring chain links are highly tensioned, the rotation between contact links, induced by the floater rotation, generates the bending moment and relevant stresses due to the unexpected bending stiffness. In 2005, the mooring chain links for the Girassol Buoy Platform were failed after just 5 months after facility installation, and the accident investigation research concluded the chain failure was mainly caused by the fatigue due to the unexpected bending stress fluctuation. This study investigates the pattern of the induced bending stiffness and stresses of the highly tensioned chain links by nonlinear finite element analysis.

본 연구는 부유식 구조물의 위치 제어를 위한 계류 체인 링크의 휨 거동에 대해 다룬다. 일반적으로 체인 구조는 링크 간 연결조건에 따라 축력만 전달하는 구조체로 인식되었다. 그러나 체인에 강한 인장력이 작용할 때, 접촉하는 두 링크 간의 마찰력에 의해 휨 강성이 도입되게 된다. 특히, 부유식 플랫폼의 계류선은 강한 인장력이 유지되는데, 물리적으로는 긴장 상태에 있는 체인 링크 간 접촉면에 마찰특성에 의해 휨 강성이 도입되면 환경하중을 받는 플랫폼에 회전 운동이 발생할 때, 계류선에도 회전 변위를 일으키고 이는 결과적으로 설계 시 고려하지 못한 휨모멘트 및 휨응력이 체인에 작용하게 된다. 실제 2005년 Girrasol Buoy 플랫폼의 해상 설치 후 5개월 만에 파손된 계류 체인의 사고 조사 시 주요 원인으로 이러한 휨 거동에 의한 부가 피로손상 누적이 지적되었다. 본 연구에서는 비선형 유한요소해석을 통해 긴장상태에 있는 체인에 도입되는 휨 강성 및 휨 응력의 특성에 대해 분석한다.

Keywords

References

  1. American Petroleum Institute (2005) Design and Analysis of Stationkeeping Systems for Floating Structures (API RP 2SK), API Publishing services, Washington DC, USA.
  2. Det Norske Veritas (2010) Position Mooring (DNV-OSE301), DNV, Norway.
  3. Det Norske Veritas (2008) Offshore Mooring Chain (DNV-OS-E302), DNV, Norway.
  4. Americal Bureau of Shipping (2009) Guide for Certification of Offshore Mooring Chain, ABS, Houston, USA.
  5. Bureau Veritas (2012) Classification of Mooring Systems for Permanent Offshore Units, Bureau Veritas, France.
  6. Jean, P., Goessens, K., and L'Hostis, D. (2005) Failure of Chains by Bending on Deepwater Mooring Systems, Proceedings of 2005 Offshore Technology Conference, OTC 17238.
  7. Cerkovnik, M., Chang, S.S., and Criffin, C. (2012) Fatigue Analysis of Tether Chain in Hybrid Risers, Proceedings of the ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, pp.799-807.
  8. Bureau Veritas (2014) Fatigue of Top Chain of Mooring Lines Due to In-plane and Out-of-plane Bendings, Bureau Veritas, France.
  9. Bastid, P. and Smith, S. (2013) Numerical Analysis of Contact Stresses between Mooring Chain Links and Potential Consequences for Fatigue Damage, Proceedings of the ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering (OMAE2013-11360).
  10. Pacheno, P.M.C.L., Kenedi, P.P., and Jorge, J.C.F. (2002) Elastoplastic Analysis of the Residual Stress in Chain Links, Proceedings of the ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering, pp.39-46 (OMAE2002-28083).
  11. Pacheno, P.M.C.L., Kenedi, P.P., Jorge, J.C.F., and Paiva, A.M.C (2003) Analysis of the Influence of Mechanical Properties on the Residual Stress in Offshore Chain Links Using the Finite Element Method, Proceedings of the ASME 2003 22nd International Conference on Offshore Mechanics and Arctic Engineering (OMAE2003-37205).
  12. Pacheno, P.M.C.L., Kenedi, P.P., Jorge, J.C.F., Santos, H.G., Savi, M.A., and Paiva, A.M.C (2003) Modeling Residual Stresses in Offshore Chain Links Using Finite Element Method, Proceedings of 17th International Congress of Mechanical Engineering (COBEM2003-0320).
  13. 임유창, 김경수, 정준모, 강찬회(2010) 부유식 해양플랜트 계류 체인의 면외굽힘 거동에 대한 연구, 대한조선학회논문집, 대한조선학회, 제47권, 제4호, pp.580-588. Lim, Y.C., Kim, K.S., Choung, J.M., and Kang, C.H. (2010) A Study on Out-of-plane Bending Mechanism of Mooring Chains for Floating Offshore Plants, Journal of the Society of Naval Architects of Korea, SNAK, Vol.47, No.4, pp.580-588. https://doi.org/10.3744/SNAK.2010.47.4.580
  14. 신태송(2006) STS 304 스체인리스강의 응력도-변형도 곡선에 관한 제안, 한국강구조학회 논문집, 한국강구조학회, 제18권, 제2호, pp. 271-278. Shin, T.S. (2006) A Proposal on the Stress-strain Curve of Stainless Steel STS304, Journal of Korean Society of Steel Construction, KSSC, Vol.28, No.4, pp.271-278.