• 한국소음진동공학회논문집
• /
• 제20권4호
• /
• pp.323-330
• /
• 2010

An efficient wave energy converter with new overtopping flow device on which spiral reefs are attached is proposed by Maritime and Ocean Engineering Research Institute in Korea and its candidate substructures such as monopile, tripod and jacket are designed. This study investigates modal characteristics of the substructures by analyzing natural frequencies and mode shapes. Based on the modal analysis results, relative strength, governing modes and some complementary design strategies of each candidate substructure are compared and discussed considering water depth conditions.

• 한국지반공학회논문집
• /
• 제35권6호
• /
• pp.39-48
• /
• 2019

본 연구는 원심모형실험을 이용해 건조 사질토 지반에 근입된 모노파일의 수평 반복하중에 대한 거동을 연구하였다. 실험에 사용된 지반 시료는 상대밀도 80%에서 마찰각이 $38^{\circ}$인 건조 주문진 표준사를 사용했다. 실험 과정은 우선 반복하중의 크기를 결정하기 위해 정적 하중 실험을 수행하여 극한하중을 결정하였다. 이를 통해 도출된 극한 하중 값의 30%, 50%, 80%, 120%을 반복하중의 값으로 결정하였고, 반복횟수는 100회로 수행되었다. 이 결과를 통해 실험 반복하중 p-y 곡선을 산정하였고 도출된 하중 별 최대 지반반력점들을 이용하여 깊이 별 반복하중 p-y 중추곡선을 도출하였다. 이를 기존 p-y 곡선과 비교 결과, 동일 깊이에서 초기기울기가 API(1987) p-y 곡선보다 과소평가 되었으며, 극한지반반력은 과대평가되었다. 또한, 동적 p-y 곡선과 비교하였을 때, 동일 깊이에서의 반복하중 p-y 중추곡선의 초기기울기와 지반반력이 작게 평가되었다. 이는 말뚝이 받는 하중 조건에 따라 p-y 곡선을 다르게 적용해야 할 것으로 판단된다.

• Wind and Structures
• /
• 제25권5호
• /
• pp.459-474
• /
• 2017

In this study an analytical expression is derived for the natural frequency of the wind turbine towers supported on flexible foundation. The derivation is based on a Euler-Bernoulli beam model where the foundation is represented by a stiffness matrix. Previously the natural frequency of such a model is obtained from numerical or empirical method. The new expression is based on pure physical parameters and thus can be used for a quick assessment of the natural frequencies of both the real turbines and the small-scale models. Furthermore, a relationship between the diagonal and non-diagonal element in the stiffness matrix is introduced, so that the foundation stiffness can be obtained from either the p-y analysis or the loading test. The results of the proposed expression are compared with the measured frequencies of six real or model turbines reported in the literature. The comparison shows that the proposed analytical expression predicts the natural frequency with reasonable accuracy. For two of the model turbines, some errors were observed which might be attributed to the difference between the dynamic and static modulus of saturated soils. The proposed analytical solution is quite simple to use, and it is shown to be more reasonable than the analytical and the empirical formulas available in the literature.

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

• 대한기계학회논문집B
• /
• 제37권8호
• /
• pp.789-798
• /
• 2013

형식인증시험을 통해 획득된 풍력발전기의 기계적 하중 데이터를 분석하기 위한 관련 프로그램 개발과 절차가 수행되었다. IEC 61400-13 규격을 기반으로 하는 측정 데이터에 대한 검증, 하중유형에 따른 분류, 시계열 및 통계 데이터 분석, 파워 스펙트럼 밀도함수 및 피로하중 스펙트럼 계산, 등가하중 계산 등의 절차가 본 프로그램을 통해 수행되었다. 수집된 데이터들이 피로하중을 산정하기에 충분한가를 판단하기 위해 정상전력생산의 경우에 대한 수집행렬을 구성하였다. 50 개의 하중 범위 분할 개수를 사용하는 우수집계법을 통해 피로하중 스펙트럼이 얻어지며, 사용된 재료에 따라 다르게 S-N 선도의 기울기를 적용하여 최종적으로 등가하중을 산출하였다. 모노파일 하부구조를 가지는 NREL 5MW 풍력발전기의 공탄성 시뮬레이션 데이터에 이용하여 위의 전반적인 절차를 수행하였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.825-839
• /
• 2010

The global and domestic market for offshore wind farm is expected to grow fast, and the design and installation of substructure and foundation is getting more important. As for the offshore wind farms located in the shallow(depth < 20m) water, the construction and installation of the substructure and foundation makes up about 1/4 ~1/3 of the offshore wind farm construction cost, and the portion is expected to increase because the turbine capacity is increasing from 2 ~ 3MW to 5MW or larger and the water depth of wind farms is also increasing over 30m. As a foundation for offshore wind turbine, the suction caisson foundation is being considered to be a highly competitive alternative to the conventional monopile or gravity based structure, because it has features suitable for the offshore construction such as quick installation, no heavy equipment for penetration and no hammering noise for driving. In order to study the installation behaviour of the suction caisson, laboratory tests were performed with sand. The pore water pressure and displacement were measured to analyze the suction pressure during penetration, the penetration speed and the amount of heaving.

• 한국태양에너지학회 논문집
• /
• 제34권2호
• /
• pp.60-65
• /
• 2014

A meteorological(met) tower is the first structure installed during the planning stages of offshore wind farm. The purpose of this paper is to design the met tower with tripod bucket type support structure and to install the sensors. The support structure consist of a central steel shaft connected to three cylindrical steel suction buckets which is more cheaper than monopile or jacket type. And the remote wind condition sensors and marine monitoring equipment, including adcp, pressure type tide gauge, wave height sensors, and scour sensors, remote power supply are installed. The manufactured met tower constructed on sea area which is in front of Gasa island. All of functions of met tower showed normal operation conditions and the wind data got by remote data collection system successfully.

• Smart Structures and Systems
• /
• 제26권4호
• /
• pp.435-449
• /
• 2020

To effectively extract the vast wind resource, offshore wind turbines are designed with large rotor and slender tower, which makes them vulnerable to external vibration sources such as wind and wave loads. Substantial research efforts have been devoted to mitigate the unwanted vibrations of offshore wind turbines to ensure their serviceability and safety in the normal working condition. However, most previous studies investigated the vibration control of wind turbines in one direction only, i.e., either the out-of-plane or in-plane direction. In reality, wind turbines inevitably vibrate in both directions when they are subjected to the external excitations. The studies on both the in-plane and out-of-plane vibration control of wind turbines are, however, scarce. In the present study, the NREL 5 MW wind turbine is taken as an example, a detailed three-dimensional (3D) Finite Element (FE) model of the wind turbine is developed in ABAQUS. To simultaneously control the in-plane and out-of-plane vibrations induced by the combined wind and wave loads, another carefully designed (i.e., tuned) spring and dashpot are added to the perpendicular direction of each Tuned Mass Damper (TMD) system that is used to control the vibrations of the tower and blades in one particular direction. With this simple modification, a bi-directional TMD system is formed and the vibrations in both the out-of-plane and in-plane directions are simultaneously suppressed. To examine the control effectiveness, the responses of the wind turbine without control, with separate TMD system and the proposed bi-directional TMD system are calculated and compared. Numerical results show that the bi-directional TMD system can simultaneously control the out-of-plane and in-plane vibrations of the wind turbine without changing too much of the conventional design of the control system. The bi-directional control system therefore could be a cost-effective solution to mitigate the bi-directional vibrations of offshore wind turbines.

• 한국구조물진단유지관리공학회 논문집
• /
• 제18권6호
• /
• pp.21-29
• /
• 2014

본 연구에서는 모노파일지지구조의 고성능 그라우트연결부의 부착거동을 다루고 있다. 강관파일 연결부의 일체화를 위하여 섬유보강 고성능 그라우트를 개발하였으며, 재령 7일 압축강도 125MPa와 직인장강도 7.5MPa를 나타내었다. 축하중을 받는 상태에서의 그라우트의 부착거동을 평가하기 위하여 강관파일에 그라우트를 충진하여 부착실험을 수행하였으며, 그 결과를 기존의 설계기준과 분석하였다. 실험변수는 섬유혼입율 (0%, 0.5% and 0.9%), 섬유의 형상비 (60 and 80)와 전단키의 높이와 간격의 비 (0.013 and 0.056)로 선정하였다. 실험결과 최대부착강도는 30.8MPa로 관찰되었으며, 섬유 혼입율보다는 전단키의 높이와 간격의 비가 부착강도에 영향을 미치는 것으로 분석되었다.

• 한국항해항만학회지
• /
• 제37권6호
• /
• pp.655-662
• /
• 2013

최근 화석 연료의 사용에 따른 문제들로 인해 다양한 그린 에너지들이 주목 받고 있다. 그린 에너지의 한 종류로써 풍력 발전의 원동력인 바람은 육상에서 보다 해상에서 양질의 값이 관측된다. 또한, 부지확보, 소음, 전자파와 같은 육상 풍력 발전의 문제점을 해결할 대안으로써, 또한 더 효율적인 풍력 발전을 위해 해상 풍력 발전의 개발이 주목받고 있다. 이에 따라 해상 풍력에 대한 많은 연구들이 수행되고 있다. 풍력 타워가 해상으로 진출함에 따라 해상 풍력 타워는 점차 거대해지고 있다. 따라서 풍력과 파력을 견뎌내기 위한 안정성이 요구되고 있다. 본 연구에서는 p-y 관계를 이용해 다층 지반의 기초에 작용하는 외력을 계산하였다.