Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Behavior of Monopile for Offshore Wind Turbine in Loose Silty Sand under Lateral Cyclic Loading via Centrifuge Model Test

원심모형실험을 활용한 느슨한 실트질 모래지반에서 해상풍력 모노파일의 반복수평하중에 대한 거동 평가

  • Lee, Jae-Kweon (Dept. of Intergrated Energy and Infrasystem, Kangwon National Univ.) ;
  • Yun, Sung-Min (Dept. of Civil Engineering, Kangwon National Univ.) ;
  • Jeon, Young-Jin (Institute of Industrial Technology, Kangwon National Univ.) ;
  • Kim, Jae-Hyun (Dept. of Civil Engineering, Kangwon National Univ.)
  • 이제권 (강원대학교 에너지인프라융합학과) ;
  • 윤성민 (강원대학교 토목공학과) ;
  • 전영진 (강원대학교 산업기술연구소) ;
  • 김재현 (강원대학교 토목공학과)
  • Received : 2024.05.31
  • Accepted : 2024.07.22
  • Published : 2024.08.31
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Abstract

Offshore wind structures are subject to long-term repeated horizontal loads from wind, waves, and currents, making it essential to consider these loads in the design of offshore foundations. In this respect, monopiles are large-diameter hollow steel pipes that are relatively simple to construct compared with piles used on onshore sites. They can provide stable support for wind structures and have well-established design codes, leading to their widespread use globally. The behavior of monopiles under lateral static loads is typically assessed using the p-y method proposed by the American Petroleum Institute (API). However, the applicability of p-y curves to large-diameter monopiles exposed to repeated cyclic horizontal loads, such as those experienced in offshore wind applications, must yet be evaluated. Thus, this study evaluated the behavior of monopiles under two-way cyclic horizontal loads in loose silty sand, a representative soil type of the southwestern coast of Korea, using centrifuge model tests. The results demostrated that the behavior of monopiles varied depending on the loading level, number of cycles, and direction of the cyclic loads. Furthermore, the p-y curve method proposed by the API overestimated the behavior of a large-diameter monopile installed in silty sand under two-way cyclic loads.

해상풍력 구조물은 파랑, 바람, 조류 등에 의한 반복수평하중에 장기적으로 노출되기 때문에 기초구조물 설계 시 이에 대한 고려가 필수적이다. 모노파일(monopile)은 일반적으로 육상에서 사용하는 말뚝에 비해 직경이 큰 중공형 강관으로 설계법이 잘 정립되어 있으며 시공이 비교적 단순하고, 안정적으로 풍력 구조물을 지지할 수 있는 장점이 있어 전 세계적으로 널리 활용되고 있다. 해상풍력 모노파일의 횡방향 정적하중에 대한 거동 평가는 American Petroleum Institute(API)에서 제안하는 p-y 곡선법을 활용하는데, 해상풍력과 같이 반복수평하중에 장기간 노출되는 경우 대구경 모노파일에 대한 p-y 곡선법의 적용성을 평가할 필요가 있다. 본 연구에서는 국내 서남해안 지역의 대표지반 중 하나인 느슨한 실트질 모래지반에서 양방향(two-way) 반복수평하중을 받는 모노파일의 거동을 원심모형실험을 통해 평가하였다. 그 결과, 모노파일의 거동은 반복하중 크기, 반복하중 횟수, 반복하중의 방향에 따라 달라지는 것을 확인하였다. 또한, API에서 제시하는 p-y 곡선법이 대구경 모노파일의 양방향 반복수평하중에 대한 거동을 과대평가하고 있음을 확인하였다.

Keywords

Acknowledgement

본 연구는 과학기술정보통신부(NRF-2021R1C1C1011540)의 재원으로 한국연구재단의 지원을 받아 수행되었으며, 이에 깊은 감사를 드립니다.

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