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Structural Design Optimization of Gageocho Jacket Structure Considering Unity Check

가거초 자켓 구조물의 허용응력비를 고려한 구조 최적설계

  • Kim, Byungmo (Department of Ocean Engineering, Korea Maritime and Ocean University) ;
  • Ha, Seung-Hyun (Department of Ocean Engineering, Korea Maritime and Ocean University)
  • 김병모 (한국해양대학교 해양공학과) ;
  • 하승현 (한국해양대학교 해양공학과)
  • Received : 2021.05.28
  • Accepted : 2021.06.28
  • Published : 2021.08.31

Abstract

Offshore jacket structures generally comprise steel members, and the safety standard for jacket structures typically focuses on the steel components. However, large amounts of concrete grouting is filled in the legs of the Gageocho jacket structure to aid in the recovery from typhoon damage. This paper proposes a safe and lightweight design for the Gageocho ocean research station comprising steel members instead of large amounts of concrete reinforcement in the legs. Based on the actual design, the structural members are grouped according to their functional roles, and the inner diameter of the cross-section in each design group is defined as a design variable. Structural optimization is carried out using a genetic algorithm to minimize the total weight of the structure. To satisfy the conservative safety standards in the offshore field, both the maximum stress and the unity check criteria are considered as design constraints during optimization. For enhanced safety confidence, extreme environmental conditions are assumed. The maximum marine attachment thickness and the section erosion in the splash zone are applied. Additionally, the design load is defined as the force induced by extreme waves, winds, and currents aligned in the same direction. All the loading directions surrounding the structure are considered to design the structure in a balanced and safe manner. As a result, compared with the current structure, the proposed structure features a 45% lighter design, satisfying the strict offshore safety criteria.

가거초 해양과학기지 자켓 구조물 내 콘크리트를 배제하고 강재로만 이루어진 최적설계를 제시한다. 50년 재현주기 극한하중조건에서 허용응력 및 허용응력비 조건을 모두 만족하는 안전한 경량 설계를 목표하였다. 역할에 따라 부재를 세 그룹으로 나눈 설계 조건(Case-1)과 보다 세분화한 설계 조건(Case-2)에 대해 각 부재그룹별 현재 단면 두께 대비 두께 변화율을 설계변수로 설정한 유전 알고리즘을 통해 최적설계를 탐색하였다. 그 결과 Case-1의 결과로 현재 가거초 해양과학기지보다 약 217톤 더 가벼운 설계(OPT-1)를 찾았고, Case-2에서는 추가적으로 약 84톤을 경량화하여 현재 대비 약 45%의 무게를 절감한 설계(OPT-2)를 얻을 수 있었다. 결론적으로 레그 내 콘크리트 보강 없이도 극한조건에서 허용응력 및 허용응력비를 모두 만족시킬 수 있는 경량화된 가거초 해양과학기지 설계를 제시하였다.

Keywords

Acknowledgement

이 성과는 정부(과학기술정보통신부)의 재원으로 한국연구재단의 지원을 받아 수행된 연구임(No. NRF- 2021R1F1A1048396; No. NRF- 2021R1C1C200971911).

References

  1. American Institute of Steel Construction (AISC) Inc. (1989) Allowable Stress Design and Plastic Design, 9th edition.
  2. American Petroleum Institute (API) (1996) Recommended Practice for Planning Designing, and Constructing Heliports for Fixed Offshore Platforms, 4th edition.
  3. ANSYS Inc. (2017) ANSYS Mechanical APDL Command Reference Release 17.1.
  4. Atkins Engineering Services (1990) Fluid Loading on Fixed Offshore Structures, OTH 90 322.
  5. Dawson, T.H. (1983) Offshore Structural Engineering, New Jersey : Prentice-Hall.
  6. Deb, K. (2000) An Efficient Constraint Handling Method for Genetic Algorithms, Comput. Methods Appl. Mech. & Eng., 186(2-4), pp.311~338. https://doi.org/10.1016/S0045-7825(99)00389-8
  7. Det Norske Veritas (DNV) (2001) Helicopter Decks, DNV-OS-E401.
  8. Engineering Dynamics, INC. (1995) SACS IV Release 4 User's Manual.
  9. Jung, T.-W., Kim, B.-M., Ha, S.-H. (2017) A Study on Lightweight Design of Cantilever-type Helideck Using Topology Optimization, J. Comput. Struct. Eng. Inst. Korea, 30(5), pp.453~460. https://doi.org/10.7734/COSEIK.2017.30.5.453
  10. Kim, B., Kim, C., Yi, J.-H. (2019) Model Updating for Gageocho Ocean Research Station Structure Using Structural Dynamic Characteristics, J. Coast. Disaster Prev., 6(3), pp.103~110. https://doi.org/10.20481/kscdp.2019.6.3.103
  11. Kim, W., Yi, J.H., Min, I.K., Shim, J.S. (2017) Estimation of Dynamic Characteristics of Gageocho Ocean Research Station using Long-term Measurement Data, Journal of Coastal Disaster Prevention, 4(5) [Special issue], pp.263~270. https://doi.org/10.20481/kscdp.2017.4.5.263
  12. Kim, W.C., Chung, T.J. (2014) Topology Optimization of Offshore Wind-Power Turbin Substructure using 3D SolidElement Model, Trans. Korean Soc. Mech. Eng. A, 36(3), pp.309~314.
  13. Sim, K., Kim, B., Kim, C., Ha, S.-H. (2019) Structural Design Optimization of Lightweight Offshore Helidecks Using a Genetic Algorithm and AISC Standard Sections, J. Comput. Struct. Eng. Inst. Korea, 32(6), pp.383~390. https://doi.org/10.7734/COSEIK.2019.32.6.383
  14. The MathWorks, Inc. (2015) MATLAB and Global Optimization Toolbox Release 2015a, Natick, Massachusetts, United States.
  15. Woo, C., Sin, J. (2012) Precision Safety Diagnosis and Disaster Recovery Design of Gageocho Ocean Research Station, Report No. BSPE98689-10169-7, Korean Ocean Research & Development Institute, 2012.