• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1908-1914
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• 2012

As the turbine capacity and the water depth of wind farms are increasing, the construction cost of substructures and foundations for offshore wind turbines is expected to increase. Since the installation of suction bucket foundation is achieved by both self-weight and applied suction, the construction generally does not require heavy equipment for penetration. This study provides an economic analysis on the tripod which have the bucket foundations and compares that the jacket foundation at 50m water depth on sand layer or soft layer. As the strength of the soil and the number of the foundation is increasing, the construction cost of the tripod with the bucket foundations is more economically feasible than the jacket foundation.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.5
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• pp.263-270
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• 2021

In this study, a reliability-based design optimization of a 130-m class fixed-type offshore platform, to be installed in the North Sea, was carried out, while considering environmental, material, and manufacturing uncertainties to enhance its structural safety and economic aspects. For the reliability analysis, and reliability-based design optimization of the structural integrity, unity check values (defined as the ratio between working and allowable stress, for axial, bending, and shear stresses), of the members of the offshore platform were considered as constraints. Weight of the supporting jacket structure was minimized to reduce the manufacturing cost of the offshore platform. Statistical characteristics of uncertainties were defined based on observed and measured data references. Reliability analysis and reliability-based design optimization of a jacket-type offshore structure were computationally burdensome due to the large number of members; therefore, we suggested a method for variable screening, based on the importance of their output responses, to reduce the dimension of the problem. Furthermore, a deterministic design optimization was carried out prior to the reliability-based design optimization, to improve overall computational efficiency. Finally, the optimal design obtained was compared with the conventional rule-based offshore platform design in terms of safety and cost.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.2
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• pp.74-82
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• 1998

To evaluate the reliability against fatigue failure of offshore structures, a fatigue reliability analysis model based on the probabilistic approach has been developed. In this model, the simplified method is adopted as a fatigue analysis method. The uncertainties included in the fatigue analysis are considered as random variables and their statistical properties are evaluated as quantitatively as possible using existing data. As an example, the developed fatigue reliability model is applied to the jacket. And then the relative significance of each uncertainty on the probability of fatigue failure is surveyed.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.37.2-37.2
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• 2011

Nowadays, offshore wind energy experiences a rapid development because of its wind condition and no noise impact problem. Different from Europe, offshore wind is just started in Asia. More work and research are needed in Korea. In this work, a three-bladed upwind variable speed pitch controlled 5MW wind turbine on a jacket support structure is used. During the simulation, several design load cases are investigated in two different fully coupled aero-hydro-servo-elastic codes. Some critical loads on the foundation are compared and analyzed.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.287-293
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• 2016

This paper presents an effective damage detection method for offshore jackets using natural frequency change ratios. Two parameters, cosine similarity and magnitude index, are considered to estimate the location and severity of the damage in the structure. A numerical jacket structure model is considered to verify the performance of the proposed method. As observed through analysis, the damages in the structure are detected accurately.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.373-381
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• 2015

As offshore structures such as offshore wind and offshore platforms have been installed frequently in ocean, scour effects are considered important. To test the scour effect, numerical simulation of scour has been carried out. However, the test was usually conducted under the uni-directional flow without bi-directional current flow in western sea of Korea. Thus, in this paper, numerical simulations of scour around offshore jacket substructure of HeMOSU-1 installed in western sea of Korea are conducted using FLOW-3D. The conditions are uni-directional and bi-directional flow considering tidal current. And these results are compared to measured data. The analysis results for 10,000 sec show that under uni-directional conditions, maximum scour depth was about 1.32 m and under bidirectional conditions, about 1.44 m maximum scour depth occurred around the structure. Meanwhile, about 1.5~2.0 m scour depths occurred in field observation and the result of field test is similar to result under bi-directional conditions.

• Journal of Ocean Engineering and Technology
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• v.28 no.3
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• pp.218-226
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• 2014

Since the support structure of an offshore wind turbine has to withstand severe environmental loads such as wind, wave, and seismic loads during its entire service life, the need for a robust and reliable design increases, along with the need for a cost effective design. In addition, a robust and reliable support structure contributes to the high availability of a wind turbine and low maintenance costs. From this point of view, this paper presents a design process that includes design optimization and reliability analysis. First, the jacket structure of the NREL 5-MW offshore wind turbine is optimized to minimize the weight and stresses, while satisfying the design requirements. Second, the reliability of the optimum design is evaluated and compared with that of the initial design. Although the present study results in a new optimum shape for a jacket support structure with reduced weight and increased reliability, the authors suggest that the optimum design has to be accompanied by a reliability analysis during the design process, as well as reliability based design optimization if needed.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.8
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• pp.1107-1114
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• 2010

In this paper, a development of a new 5 d.o.f. underwater manipulator which is actuated by electric motors capable of carrying over 20kg payload and of various operation under the water has been studied. The manipulator for applying to midium-sized AUV or ROV has been designed small and light but to handle a heavy 25kg payload. The joint actuator for the manipulator is designed and builted as a new modular typed double oil jacket for waterproofness. Also, superior joint torque performance of the developed joint actuator has been varified through tests in the air. And, a 5 d.o.f. highly perfomable underwater manipulator has been builted applying the developed underwater joint actuators.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.4
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• pp.375-384
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• 2015

Recently, construction sites of offshore wind power tend to move from shallow water to deep water. From this tendency, the research on the support structure of offshore wind power in deep water will be a key issue. In this study, precast concrete block and suction pile are applied to existing jacket structure. In order to reduce the vibration of this structure, the tuned liquid damper is also applied in the precast concrete block. The applicability of the suggested jacket structure is evaluated by finite element analysis. And the vibration tends to decrease about 5%, when the tuned liquid damper is applied.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.185.1-185.1
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• 2010

The 3MW OWEC demonstrator project in Korea will be the first offshore wind project with Korean turbine, Doosan WinDS3000, and constructed on the north-eastern sea of Jeju Island as the water depth of 15m. Integrated loadings of wind and wave are investigated to describe a design loads for both extreme and fatigue conditions using GH-Bladed. A dynamic behaviour of substructure strongly affects a substructure loadings. The jacket structure is designed in accordance with DNV guidelines. The results of this paper show overall design process of offshore substructure as a complex jacket concept and this design process can be implemented on a design of monopile and tripod structures.