• 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 Society of Marine Environment & Safety
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• v.24 no.7
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• pp.841-847
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• 2018

Since global energy consumption and demand for energy have dramatically risen, a focus on environmental problems and sustainability has become more important. Clean and renewable energy sources such as offshore wind power generation have received attention among new renewable energy options as alternative energy resources. Due to maintenance and operational perspectives, offshore wind farms have been planned for installation in many coastal waters. However, development of offshore wind farms faces interference from existing maritime traffic along the planned areas. In order to safely and effectively govern marine traffic in the vicinity of wind farms and inner areas, standard criteria are suggested to allow vessels to sail the internal waters of offshore wind farm areas. Therefore, the purpose of this study is to establish allowable criteria for sailing vessels and safety zones for offshore wind farms by investigating the local regulations of various offshore wind farm cases overseas. The commended inner safety zone of wind farms is proposed to be a distance of 150 % of the rotation diameter of the wind turbine rotor and a distance of 200 m from the outer wind turbine for the outer safety zone. Besides this, the allowable criteria for sailing vessels within a wind farm is proposed to have an air draft of 14.47 m south-west wind farm sea areas for a minimum margin to avoid hull contact through evaluation of the tide and height of a wind turbine. further studies will be needed to establish vessel sailing criteria among adjacent offshore wind farms as well as vessel sailing criteria within a single offshore wind farm.

• Journal of Ocean Engineering and Technology
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• v.36 no.6
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• pp.353-363
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• 2022

The azimuth thruster is mainly installed on a vessel that requires a dynamic positioning (DP) function for special purposes. When the azimuth thruster on a vessel operates for DP, the thrust loss is induced by the thruster-hull interaction. This study examined the influence of boundary conditions in numerical simulations for predicting thrust loss. Wind turbine installation vessels (WTIV) and floating production storage and offloading (FPSO) were chosen as a target vessels. In this study, two types of boundaries were defined. The first consideration is that the boundary condition was assigned with consideration of the azimuth angle of the thruster, whereas it is fixed regardless azimuth angle of the thruster. The predicted thrust loss according to these boundary conditions showed a difference. This observation originated from the current load of the vessel. Therefore, the boundary conditions for which the current load is not induced need to be designated to obtain a realistic thrust loss in a numerical simulation.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.11-15
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• 2016

YP 690MPa grade steels are used as the main structural steel for offshore structure such as Jack-up Rig and WTIV(Wind Turbine Installation Vessel). Most of welding consumables applied to YP 690MPa grade steels are basic type flux cored wires that shows the poor weldability and not suitable for all position welding. For this reason, welding consumables with rutile type flux system is required. Rutile type flux cored wires show excellent weldability and apply to all position welding. This paper presents the mechanical properties of weld metal with rutile type flux cored wire developed and finally assessed the possibility for application.

• Journal of Ocean Engineering and Technology
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• v.29 no.2
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• pp.175-185
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• 2015

Jack-up type WTIV(Wind Turbine Installation Vessel) is used to avoid the effects of waves when installing wind turbines in the Southwest Sea of South Korea. During the preloading procedure, unexpected penetration may cause some risks such as excessive penetration or punch-through failure. To ensure the safety of the WTIV during preloading, the bearing capacities should be evaluated based on the soil data at each borehole. Eight boreholes (OW-1 to -8) have been drilled in the Southwest Sea of South Korea. The bearing capacities of a spudcan designed to be used in this district are calculated using both a conventional analysis and finite element analysis with the soil properties of OW-1 to -8. A finite element analysis is carried out for OW-1, -3, and -4 to gain an in-depth understanding of the soil behavior during the penetration. OW-1, -3, and -4 are representative boreholes for a strong layer overlying a soft layer, a general soft layer, and a soft layer overlying a strong layer, respectively. The resultant bearing capacity curves versus the depth of the numerical analysis are compared with the conventional method. The results show that the conventional analysis is conservative. Case studies for different spudcan areas and shapes are also conducted to seek an appropriate spudcan type for the Southwest Sea of South Korea. Finally, a spudcan with a rectangular shape and a bearing area of $112.8m^2$ is selected.