• Journal of Fisheries and Marine Sciences Education
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• v.29 no.3
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• pp.689-701
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• 2017

In recent offshore industries, various ambiguous terms have been used without clear definition or classification, causing difficulties in legal, technical, and educational understanding and usage. For an example, the commonly used term of 'Offshore Plant' in Korea is not an universal word technically. There has been no clear technical or legal definition about the 'Offshore Plant' and its classification is also very ambiguous; sometimes it is used to refer offshore oil and gas production platform or it is used to mean offshore renewable power generation plant in some cases. To build a conceptual framework, therefore, this paper suggests a classification of offshore units (1) using internationally agreed terms, (2) agreed with the technical classification used by the ship classification society and (3) being able to include not only the current but also future concepts of offshore units.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.344-352
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• 2019

Marine production strings are continuously affected by unstable internal fluid during operation. In this paper, the structural governing equation for marine production string self-induced vibration is constructed. A finite element analysis model is established based on Euler-Bernoulli theory and solved by the Newmark method. Furthermore, based on reliability theory, a self-design procedure is developed to determine the operability envelope for marine production string self-induced vibration. Case studies show: the response frequency of the production strings is consistent with the excitation frequency under harmonic fluctuation and mainly determined by the first-order natural frequency under stochastic fluctuation. The operability envelope for marine production string self-induced vibration is a near symmetrical trapezium. With the increasing of natural gas output, the permissible fluctuation coefficient dramatically decreases. A reasonable centralizer spacing, increasing top tension, and controlling natural gas output are of great significance to the risk control in marine production string operation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.48-55
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• 2019

With recent rapid increases in the power generation capacity of offshore wind power generators, reliable structural analysis of the large-scale infrastructure needed to install wind power generators at sea is required. Therefore, technology for heavy marine equipment such as barges and excavation equipment is needed. Under submarine conditions, rock drilling technology to install the substructure for offshore wind pile excavation is a very important factor in supporting a wind farm safely under dynamic loads over periods of at least 20 years. After investigating the marine environment and on-site ground excavation for the Saemangeum offshore wind farm, in this study we suggest.

• Journal of Ocean Engineering and Technology
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• v.34 no.4
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• pp.263-271
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• 2020

In this study, we performed a three-dimensional (3D) topology optimization of a fixed offshore structure to enhance its structural stiffness. The proposed topology optimization is based on the solid isotropic material with penalization (SIMP) method, where a volume constraint is applied to utilize an equivalent amount of material as that used for the rule-based scantling design. To investigate the effects of the main legs of the fixed offshore structure on its structural stiffness, the leg region is selectively considered in the design domain of the topology optimization problem. The obtained optimal designs and the rule-based scantling design of the structure are manufactured by 3D metal printing technology to experimentally validate the topology optimization. The behaviors under compressive loading of the obtained optimal designs are compared with those of the rule-based scantling design using a universal testing machine (UTM). Based on the structural experiments, we concluded that by employing the topology optimization method, the structural stiffness of the structure was enhanced compared to that of the rule-based scantling design for an equal amount of the fabrication material. Furthermore, by effectively combining the topology optimization and rule-based scantling methods, we succeeded in enhancing the structural stiffness and improving the breaking load of the fixed offshore structure.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.166-167
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• 2005

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.3
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• pp.231-241
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• 2017

The purpose of this study was to analyze traffic safety assessments for fishing vessels near the southwest offshore wind farm. This study applied a collision model for safety assessment. It also involved a spatiotemporal analysis of vessels engaged in fishing to identify fishing hotspots around the offshore wind farm. This study used data from fishing vessel location transmission devices gathered over 1 year in 2014. As a result, in September, when the average number of vessels engaged in fishing is high, 62 ships were operating in fishing section 184-6 and 55 ships in section 184-6. In addition, in fishing sections 184-8 and 192-2, where an offshore wind farm was located, there were 55 and 38 ships operating, respectively. As the recovery period for a seaway near wind farm turbines is 55 years, it was determined that safety measures are required in order to reduce collision frequency while allowing fishing vessels to navigate through offshore wind farms. Meanwhile, the return period of Seaway B between the groups of generators considered was 184 years. A safety zone for offshore wind farms should be installed covering a distance of at least 0.3 NM from the boundary of turbines. Then, the collision return period was derived to be close to 100 years. Through this traffic safety assessment, it has been concluded that such measures would help prevent marine accidents.

• Ocean and Polar Research
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• v.28 no.2
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• pp.67-78
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• 2006

Six surface sediments from two offshore transects of Ulsan and Gampo, on the southeastern margin of Korea were taken for sediment and foraminiferal analyses. Sedimentary processes are dominated by reworking and resedimentation from storms in the area off Ulsan and hemipelagic suspension settling in the area off Gampo. Eighty-four foraminiferal species were identified in total assemblages, including 33species of living populations and 9 species of planktonic foraminifera. The characteristics of foraminifera showed differences of offshore environments between Ulsan and Gampo. The number of living species, species diversity and equitability in Gampo offshore area had higher values than those in Ulsan offshore area. However, planktonic/benthic(P/B) ratio showed higher in the Ulsan offshore area. The species diversity indices and P/B ratio indicated that environmental stability and surface-ocean productivity in the Gampo offshore area were relatively higher than the Ulsan offshore area. The difference of species compositions is useful for interpreting the paleoenvironments in mud deposits of the southeastern margin of Korea.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.611-622
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• 2007

In the design and construction of the coastal/offshore structures, it is very important to evaluate the geotechnical characteristics of marine soils, which support the structures. Although the offshore site investigation is much more difficult than onshore, safe and precise jobs have not been accomplished in Korea because of the insufficiency of the test equipments especially for the site with deep water depth. The main objective of this study is to develop a new type of marine cone penetration testing(CPT) system, which can be utilized to even deep sea and high depth of soil layer. The system is one of seabed types and employs the conventional cone, which shows more reliable results than miniature cone. The most important parts of the marine CPT including continuous rod system, cone penetration system with wheel drive, automatic cone rod assembly/dissembly system etc., were designed and manufactured. Some tests to verify the developed marine CPT system were performed at both onshore and offshore sites as well as mechanical test in laboratory. The test results show the consistent and promising performance of the new equipment, and thereafter the system would be applicable to various sites with practical/economical advantages.

• Journal of Environmental Impact Assessment
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• v.28 no.3
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• pp.312-331
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• 2019

An offshore waste disposal facility refers to a landfill site for final landfilling of stabilized inorganic solid waste such as land and marine waste incineration materials, and the aim of such a facility is to solve the problem of insufficient waste disposal space on land and create and develop environmentally friendly marine spaces. The purpose of this study is to prepare guidelines for the construction of offshore waste disposal facilities, which reflect the need and importance of paying sufficient heed to environmental considerations from the initial stage of the project, in order to investigate, predict, and assess how such guidelines will affect the marine environment in relation to the construction of offshore waste disposal facilities, with the goal of minimizing the impact on and damage to the environment. For the purpose of this research, guidelines focusing on the construction of offshore waste disposal facilities were derived through an analysis of domestic cases and similar foreign cases and an assessment of their level of compliance with existing EIA guidelines through the operation of a discussion forum. In order to review the EIA report on similar cases in Korea, 17 EIA documents (2005~2016) for dredged soil dumping areas and ash ponds of thermal power plants were analyzed to investigate the status of marine organisms, marine physics, marine water quality, and marine sediment and to understand what types of problems can occur and what improvement measures can be taken. The purpose of these guidelines were to minimize damage to the marine environment by promoting EIA protocols in accordance with scientific and systematic procedures, to reduce the consultation period related to projects, to resolve social conflicts, and to reduce economic costs.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.242-251
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• 2013

Recently, while global concern over offshore resources exploration and development is being increased rapidly, offshore plant industry is highlighted as an industry of high added value. Along with this global trend, domestic concern over offshore plant development is being increased as well. In the overseas case, a marine geotechnical survey guideline for confirming characteristics of seabed sediments is available at the time of installation of offshore plant but such guideline is not available in our country. In this study, survey techniques fit for domestic marine environment was applied according to overseas guideline at southern coastal area, Korea. Among the marine geophysical survey techniques being proposed abroad, magnetic survey and seabed photograph were excluded. However, highly reliable data analysis was enabled for marine geophysical survey, which includes in-situ coring investigation and laboratory soil test. In addition, continuous ocean current survey was included to find scour potential due to the current around the offshore plant. Although coring depth is not so deep, we predicted geological structure through the analysis of amplitude features of seismic data. Characteristics of seabed sediments cold be obtained regionally and directly through combined analysis of marine geophysical survey data and coring data.