• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.494-503
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• 2010

This paper reviews research trend in suction bucket foundation. Wind energy farm has been considered as an efficient alternative to fuel energy as world markets attempt to discover renewable resources. Recently, Korean government initiated the research projects investigating installation method of offshore wind energy foundation and design guideline as well as verifying feasibility of offshore wind farm. In fact, the installation of monopile and gravity type foundation has been sucessfully carried out in European and other advanced countries, and design guideline of those foundations are well established; however, various types of foundation would be necessary in the near future as offshore wind farm demands abundant wind resources in deep sea. In this paper, bucket foundation is spot lighted as a powerful and economic alternative applicable to deep sea condition.

• 한국해양공학회지
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• 제29권5호
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• pp.359-365
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• 2015

A reliability analysis of the gravity-based foundation of anoffshore wind turbine was performed by considering the uncertainties of the design variables, including environmental loads. The limit state functions of the gravity-based foundation were defined using the response limits of the support structures suggested in the DNV standard. The wind load couldbe obtained using the GH_bladed software, and the wave load was calculated using the Morison equation. Then, the extreme distributions of the wind and wave loads were estimated by applying the peak over threshold (POT) method to the wind and wave load data. The probability distribution characteristics of the soil properties were defined with reference to a southwest coast geotechnical survey report. The reliability index was evaluated for each failure mode using a first-order reliability method.

• 한국산학기술학회논문지
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• 제13권3호
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• pp.1346-1351
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• 2012

해상풍력발전기초의 국부세굴을 평가하기 위하여 3차원 수치해석인 FLOW-3D를 이용하여 모노파일과 자켓기초에 대해 해석을 수행하였다. 수치해석 결과에 의하면 모노파일과 자켓기초 레그 주위에서 국부적으로 유속이 증가하는 것으로 나타났으며, 그 후면에서는 후류 및 와류로 인하여 유속의 감소가 나타났다. 자켓기초의 경우에는 모노파일에 비해 단일 레그의 직경이 작고, 자켓레그 사이의 간섭효과 및 자켓구조물의 복잡한 형상으로 인하여 모노파일에 비하여 국부적인 유속 증가가 더 크게 나타났으며 세굴심이 더 깊게 형성되는 것으로 나타났다. 따라서, 해상풍력발전 기초의 세굴 평가 및 세굴방지공 설계시 하부구조물의 형상에 대한 고려가 필요한 것으로 판단된다.

• 한국산학기술학회논문지
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• 제13권4호
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• pp.1908-1914
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• 2012

풍력발전기의 용량이 점차 대형화되고 해상풍력단지는 수심이 깊은 곳에 조성됨에 따라 해상풍력발전구조물의 하부구조 및 기초시공비용 또한 급격히 증가될 것으로 예상된다. 석션버켓기초는 버켓형식의 기초를 자중에 의한 관입과 자중관입 이후 석션에 의한 관입으로 설치하는 공법이며, 대형장비 대신 충분한 용량의 펌프만 있으면 기초의 시공이 가능하므로 시공이 간편하고 경제적인 공법으로 알려져 있다. 본 연구에서는 석션버켓기초의 경제성을 검토하기 위하여 상부지반이 사질지반과 연약지반인 경우일 때 대수심 조건에 적용 가능한 기초형식인 자켓과 석션버켓기초를 적용한 트라이포드의 시공비용을 비교하였다. 그 결과 지반이 단단하고, 기초개수가 증가할수록 자켓형식보다는 트라이포드 버켓기초형식을 적용하는 것이 더 경제적임을 확인하였다.

• 한국지반환경공학회 논문집
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• 제20권12호
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• pp.41-47
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• 2019

본 논문에서는 서남해 해상풍력 실증단지 해역을 대상으로 석션버켓기초의 지지력에 대한 신뢰성 분석에 대한 내용을 다루었다. 5MW급 해상풍력터빈의 콘크리트 석션버켓기초를 선정하여 기초 설치 후 연직지지력과 수평지지력에 대한 파괴확률을 계산하고 설계변수의 민감도를 분석하였다. AFOSM을 이용한 신뢰성해석을 수행한 결과, 기초-지반 분리거동 시 연직지지력에 대한 파괴확률이 가장 큰 것으로 나타났으며 기초지반의 단위중량과 내부마찰각이 지배적인 영향인자임을 확인하였다.

• Smart Structures and Systems
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• 제23권5호
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• pp.405-420
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• 2019

In this study, vibration characteristics of offshore wind turbine tower (WTT) with gravity-based foundation (GBF) are identified from dynamic responses under wave-induced excitations. The following approaches are implemented to achieve the objective. Firstly, the operational modal analysis methods such as frequency domain decomposition (FDD) and stochastic subspace identification (SSI) are selected to estimate modal parameters from output-only dynamic responses. Secondly, a GBF WTT model composed of superstructure, substructure and foundation is simulated as a case study by using a structural analysis program, MIDAS FEA. Thirdly, wave pressures acting on the WTT structure are established by nonlinear regular waves which are simulated from a computational fluid software, Flow 3D. Wave-induced acceleration responses of the target structure are analyzed by applying the simulated wave pressures to the GBF WTT model. Finally, modal parameters such as natural frequencies and mode shapes are estimated from the output-only acceleration responses and compared with the results from free vibration analysis. The effect of wave height and period on modal parameter extraction is also investigated for the mode identification of the GBF WTT.

• Wind and Structures
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• 제21권6호
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• pp.597-607
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• 2015

With an increasing demand of a renewable energy, new offshore wind turbine farms are being planned in some parts of the world. Foundation installation asks a significant cost of the total budget of offshore wind turbine (OWT) projects. Hence, a cost reduction from foundation parts is a key element when a cost-efficient designing of OWT budget. Mono-piles have been largely used, accounting about 78% of existing OWT foundations, because they are considered as a most economical alternative with a relatively shallow-water, less than 30 m of seawater depth. OWT design standards such as IEC, GL, DNV, API, and Eurocode are being developed in a form of reliability based limit state design method. In this paper, reliability analysis using the response surface method (RSM) and numerical simulation technique for an OWT mono-pile foundation were performed to investigate the sensitivities of mono-pile design parameters, and to find practical implications of RSM reliability analysis.

• 한국해양공학회지
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• 제31권4호
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• pp.281-287
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• 2017

In the case of fixed offshore wind turbines, scouring phenomena have been reported around sub-structures as a result of currents, which seriously damage the structural stability. A parametric study of the various sub-structures of a fixed offshore wind turbine was performed to investigate their effects on the scouring phenomena. For a suction bucket foundation and monopile, the effects of the stick-up heights and water depth were studied, respectively. The open source libraries, called OpenFOAM, were used to simulate a violent flow around a foundation. The numerical methods were selected based on a two-dimensional analysis of a suction bucket. Based on the results for various stick-up heights, a larger scouring region was observed with an increase in the stick-up height because of the down-wash flow around a foundation. Based on the results for various monopile water depths, the water depth had an insignificant effect on the scouring.

• 한국해양공학회지
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• 제38권2호
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• pp.74-85
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• 2024

Offshore wind turbines are supported by various foundations, each with its considerations in design and construction. Gravity, monopile, and suction bucket foundations encounter geotechnical issues, while jacket and tripod foundations face fatigue problems. Considering this, a gravity foundation based on a steel skirt was developed, and a monopile foundation was analyzed for Pile-Soil Interaction using the p-y curve and 3D finite element method (3D FEM). In addition, for suction bucket foundations, the effects of lateral and vertical loads were analyzed using 3D FEM and centrifuge tests. Fatigue analysis for jacket and tripod foundations was conducted using a hotspot stress approach. Some hybrid foundations and shape optimization techniques that change the shape to complement the problems of each foundation described above were assessed. Hybrid foundations could increase lateral resistance compared to existing foundations because of the combined appendages, and optimization techniques could reduce costs by maximizing the efficiency of the structure or by reducing costs and weight. This paper presents the characteristics and research directions of the foundation through various studies on the foundation. In addition, the optimal design method is presented by explaining the problems of the foundation and suggesting ways to supplement them.

• 한국재난정보학회 논문집
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• 제8권2호
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• pp.138-147
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• 2012

본 논문에서는 해상풍력발전타워와 선박충돌에 대한 다양한 매개변수에 해석을 수행하여 선박충돌시 버켓파일로 지지된 기초부와 상부타워의 극한하중에 대한 거동을 분석하였다. 또한 충돌에너지의 변화에 따른 버켓기초의 안정성 여부 및 풍력타워의 에너지 소산능력에 대해 파악하였다. 해석결과 선박이 충돌에너지는 주로 타워의 소성변형에너지에 의해 소산 되었으며 이러한 극한상태의 하중에도 기초부는 충분한 지지력을 보이는 것으로 나타났다.