• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.141-152
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• 2022

As interest increases related to the development of eco-friendly energy, the offshore wind turbine market is growing at an increasing rate every year. In line with this, the demand for an installation vessel with large scaled capacity is also increasing rapidly. The wind turbine installation vessel (WTIV) is a fixed penetration of the spudcan in the sea-bed to install the wind turbine. At this time, a review of the spudcan is an important issue regarding structural safety in the entire structure system. In the study, we analyzed the current procedure suggested by classification of societies and new procedures reflect the new loading scenarios based on reasonable operating conditions; which is also verified through FE-analysis. The current procedure shows that the maximum stress is less than the allowable criteria because it does not consider the effect of the sea-bed slope, the leg bending moment, and the spudcan shape. However, results of some load conditions as defined by the new procedure confirm that it is necessary to reinforce the structure to required levels under actual pre-load conditions. Therefore, the new procedure considers additional actual operating conditions and the possible problems were verified through detailed FE-analysis.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.3
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• pp.196-203
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• 2017

In general, the installation of offshore wind turbine have been carried out by a jack-up barge or wind turbine installation vessel. In case of using jack-up barge, an additional barge is required to transport offshore wind turbines. During the transportation, barge is affected by environmental conditions such as wave, wind etc. So, it is important to secure the static and dynamic stability of the barge. In this study, fundamental research was performed to evaluate the stability of barge due to use the guide frame. The analysis for static stability of barge was performed under the two loading conditions with or without wave and those results were evaluated according to the Ministry of Oceans and Fisheries rules. Also motion analysis was performed under the ITTC wave spectrum using buoy data and evaluated based on NORDFORSK guideline by using commercial software Maxsurf Motions.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1136-1142
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• 2012

With concern for new renewable energy sources rising, the offshore wind turbine energy market is growing. In order to install offshore wind turbines safely in a harsh environment, jack-up rigs need to be used. Recently, a WTIV(Wind Turbine Installation Vessel), which has a self-propelling system, was developed to replace traditional jack-up rigs. Since the jack-up rig works at 60 meters of depth in offshore and the seafloor is composed mostly of soft clay and sand, it is necessary to conduct a stability examination for ground subsidence before using it. This study conducts an improved numerical analysis of the effect of jack-up rig loading on the soft ground by using FLAC3D considering consolidation theory. This includes analyzing the amount of subsidence when applying different cases of surchargings. It can be concluded that the mid-loading method has an advantage as regards clay layers and the pre-loading method has an advantage as regards sand layers.

• Journal of the Korean Solar Energy Society
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• v.31 no.3
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• pp.29-35
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• 2011

This study draws economic expense factors according to the influence of generation resulted from slipstream and the arrangement of the complex when arranging and designing the complex for offshore windpower development as a model of 50MW offshore wind farm and conducts economics analysis. According to the result of the analysis, O (Optimize) arrangement was the one that has the highest generation for having the best windpower resources in terms of design and being least affected by slipstream; however, the arrangement requires expensive submarine cables and high installation cost. Therefore, according to the analysis of economics, it was thought that 50MW complex should have less economics as BC ratio 0.95 than the series arrangement of main wind direction and I+80 series arrangement would be rather more economical. This economics evaluation provides comparison according to the arrangement of the development complex considering the uncertainty of the electricity price and gross construction cost. And it is expected that the result of economics evaluation would greatly differ by installation capacity, and the reason is that the cost of electric infrastructure takes up a higher portion than the gross construction cost of the development complex. The only way to compensate this part is to make the windpower development complex larger. It seems that it will be necessary to enhance spot applicability to evaluate economics afterwards and pay consistent attention to and conduct follow-up research on the economics evaluation of the complex construction.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.3
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• pp.72-77
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• 2014

The cross-section area of cable in the Offshore Wind Farm (OWF) is smaller than that in the onshore wind farm. Because the power loss in OWF is large relatively, the power loss is a key element for the economic evaluation of OWF design. The availability of wind turbine in OWF and the size of OWF are larger than those of onshore wind farm. If the economic evaluation of OWF ignores the availability of wind turbines, the power loss cost of OWF is overpriced. Since there are so many wind turbines, also, the calculation of power loss should be more accurate. In this paper, a method to calculate power loss is proposed for the design of big and complex inner-grid in OWF. The 99.5MW OWF is used for case study to see what effect the proposed method have on the power loss cost.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.5
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• pp.39-45
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• 2013

Wind power is one of the fastest growing renewable energy sources. In these days, wind turbine shifts from onshore to offshore because the offshore wind farm has a abundant wind resource. However, offshore wind turbine is not easy to access, it has a long downtime when the failures of the wind turbine component occur. Therefore, the appropriate wind turbine maintenance plan is required to meet the economic and reliability of the components. This paper proposes the maintenance planning method based on the RCM(Reliability Centered Maintenance) to determine an economical maintenance cycle to satisfy the appropriate reliability of the wind turbine components. In order to compare the proposed method with the conventional RCM method, critical components are selected in the case study because they have a long downtime and a large amount of total cost.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.68-72
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• 2001

Two different methods of free span analysis of offshore pipelines by DnV codes were introduced and compared in order to calculate the allowable free span lengths of the offshore pipelines. The allowable span lengths of the offshore pipelines for installation, hydrotest and operation conditions by static and dynamic span analysis were determined. Static analysis was performed by ASME codes and dynamic span analysis was performed by both 1981 DnV code. Comparison of two codes were carried out. A new design procedure to calculate the allowable span lengths was developed with new DnV code.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.141-147
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• 2001

The launching process is one of the most critical operations for large structure in offshore installation. Since as the size increases it limits the availability of offshore crane facilities, the large jacket structures are often installed by launching. As the structure approaches to tilt beam, it reaches critical load, and there are parameters to affect on launching procedure. The major influential parameters are trim, draft of barge, center of gravity, center of buoyancy and reserved buoyancy of jacket. As increasing of trim and draft, structural loads tend to decrease. The trim is found to be more contributing than draft on structural loads. Therefore the trim should be increased so as to decrease structural loads and to avoid stalling of structure and submergence of stern. During the launching process, the distance between jacket and seabed should be investigated which differs from the amount of reserved buoyancy and launching condition of barge. In this paper the effects of parameters on launching process are numerically investigated.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.1
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• pp.1-13
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• 2014

A new 5-MW floating offshore wind turbine moored by a spring-tensioned-leg was proposed for installation in about 50m water depth. Its substructure is a platform of the inverted conical cylinder type with massive ballast weight plate at the bottom. A 1:128 scale model was built for the preliminary engineering development. The model tests in waves and wind were carried out to estimate motion characteristics of this platform in the Ocean Engineering Wide Tank of the University of Ulsan. Its motions were measured and the RAOs were compared. The proposed floating offshore wind turbine showed a good stability and decent responses in waves, wind and operation of the wind turbine.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.21-26
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• 2003

The reel-lay method of submarine pipelines a continuous string of pipe coiled onto a reel. Assembly of this pipe that is string is accomplished onshore by welding, and nondestructive testing is carried out prior to coiling the pipe. The total length of pipes on the reel depends on the reel and pipe diameters. Pipeline installation is accomplished by uncoiling, straightening the pipe, and laying out the pipe string onto the seabed as the barge moves forward. Installation associated with coiling and uncoiling is related to the bending moment and strain relationship of the pipeline, A highgrade pipe material is required when the reel-lay method is used. This paper is concerned with the highly plastic bending moment of the pipeline, including the effect of ovality. Moment calculation in the pipe is accomplished by the numerical method, including the variable ovalities during the plastic bending of the pipe string. The new calculation method of the high plastic bending moment was applied to the reel-lay method.