• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.40-46
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• 2015

Arctic Ocean has rapidly melted due to global warming, by this, commercial ship has been operating through the area. Reason to develop the Northern Sea Route(NSR) even in extreme conditions, the distance than the existing route is shortened, which bring economic benefits. For these reason, the International Maritime Organization(IMO) established safety standards of the Arctic navigation(Polar Code) in order to ensure safe operation in the Northern Sea Route. In this study, it has been described ice types and safety standards of Artic vessel what officer needs to know for safe navigation on the Arctic Ocean. And It was verified by simulation the theoretical knowledge for the safe operation of the Arctic vessel. As a result, it was found that ship needs to reduce speed and analyze ice for safe operation before enter into the ice, it is necessary to enter at right angle to break ice safety and efficiently. Also according to the result of the simulation of navigation entering in ice channel(Lead), it was difficult to change course, it is believed that require emergency training for passing Vessel. In the future, It shall be analyzed precisely under various conditions of scenario.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.6
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• pp.128-137
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• 2023

In this study, the bearing pressure on the rubble mound of a gravity-based harbor structure with an arbitrarily shaped bottom was targeted. Assuming that the bottom of the structure is a rigid body, the rubble mound was modeled as a linear spring uniformly distributed on the bottom that resists compression only, and the bearing pressure evaluation formula was derived. It was confirmed that there were no errors in the derivation process by showing that when the bottom was square, the derived equation was converted to the equation used in the design. In addition, the validity of the derived equation was proven by examining the behavior and convergence value of the bearing pressure when an arbitrarily shaped bottom converges into a square one. In order to examine the adequacy of the method used in the current design, the end bearing pressure for the pre-designed breakwater cross-section was calculated and compared with the values in the design document. As a result, it was shown that the method used for design was not appropriate as it gave unsafe results. In particular, the difference was larger when the eccentricity of the vertical load was large, such as in the case of extreme design conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.14 no.1
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• pp.51-64
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• 2002

To investigate long-period wave responses in Sokcho Harbor and Cheongcho lagoon, field measurements were made for long-and short-period waves and current velocities using a Directional Waverider, a ultrasonic-type wave gauge, four pressure-type wave gauges, and a current meter. From the data analysis, it was found that the Helmholtz resonant periods of Sokcho Harbor and Cheongcho lagoon are about 13.6 and 54.5 minutes, respectively, and the dominant period of wave induced current in the passage between Sokcho Harbor and Cheongcho lagoon is about 55.2 minutes which depends on Helmholtz resonant condition of the Cheongcho lagoon. It was also found that the energy level of the far-infra-gravity waves during storm conditions is very high compared with that during calm sea conditions. To investigate relationships between far-infra-gravity waves and short-period waves at offshore station, regression analyses were carried out especially for 1) heights, 2) periods, 3) direction and height, 4) height and period between short-and far-infra-gravity waves, respectively. The results showed that the long-period wave height is highly correlated with the short-period wave height. However, no special trend was found for the other relations. In the future far-infra-gravity wave heights on return period around Sokcho Harbor region can be suggested by using extreme value analyses of long term measured data.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.135-142
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• 2015

Floating offshore structures should be designed by considering the most extreme environmental loadings which may be encountered in their design life. The most severe loading on a wave-offshore wind hybrid power generation system is wave loads. The principal parameters of wave loads are wave length, wave height and wave direction. The wave loads have different effects on the structural behavior characteristic depending on the combination of wave parameters. Therefore, the process of investigation for critical loads based on the individual wave loading parameter is need. Namely, the equivalent design wave should be derived by finding the wave condition which generates the maximum stress in entire wave conditions. Through a series of analysis, an equivalent regular wave height can be obtained which generates the same amount of the hydrodynamic loads as calculated in the response analysis. The aim of this study is the determination of equivalent design wave regarding to characteristic global hydrodynamic responses for wave-offshore wind hybrid power generation system. It will be utilized in the global structural response analysis subjected to selected design waves and this study also includes an application of global structural analysis.

• Ocean Systems Engineering
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• v.2 no.2
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• pp.99-113
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• 2012

Steel Catenary Risers (SCR) are the simplest and often the most economic solution compared to other riser types such as flexible pipe, riser towers, top tensioned risers, etc. The top of a SCR is connected to the host platform riser porch. The other end of the SCR connects to flowlines from subsea wells. The riser touchdown point (TDP), which is the location along the riser where contact with the sea floor first occurs, exhibits complex behaviors and often results in compression and fatigue related issues. Heave dynamic responses of semisubmersibles in extreme and operating sea states are crucial for feasibility of SCR application. Recent full field measurement results of a deep draft semisubmersible in Hurricane Gustav displayed the considerable discrepancies in heave responses characteristics between the measured and the simulated results. The adequacy and accuracy of the simulated results from recognized commercial software should be examined. This finding raised the awareness of shortcomings of current commercial software and potential risk in mega investment loss and environmental pollutions due to SCR failures. One main objective of this paper is to attempt to assess the importance and necessity of accounting for viscous effects during design and analysis by employing indicator of viscous parameter. Since viscous effects increase with nearly third power of significant wave height, thus newly increased metocean criteria per API in central Gulf of Mexico (GoM) and even more severe environmental conditions in Western Australia (WA) call for fundamental enhancements of the existing analysis tools to ensure reliable and robust design. Furthermore, another aim of this paper is to address the impacts of metocean criteria and design philosophy on semisubmersible hull sizing in WA and GoM.

• Journal of the Korean Data and Information Science Society
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• v.28 no.6
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• pp.1437-1445
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• 2017

This paper suggests a temperature guidance which must be addressed in the preparation of specifications for military equipment used in ocean/coastal environment of the Korean peninsula. It would often be costly to design materiel to operate under the most extreme environmental conditions ever recorded. Therefore, military planners usually accept equipments designed to operate under environmental stresses for all the time except a certain small percentage of the time. In this study, an 1-percent frequency of occurrence is recommended. Pohang and Shineiju are chosen to represent the hottest and coldest regions, respectively, based on surface weather observations among 28 costal regions from 1904 to 2015. The 1st and 99th percentile temperatures for Pohang and Shineiju are $37.7^{\circ}C$ and $-23.7^{\circ}C$, respectively. Diurnal cycles, including solar radiation, relative humidity and wind-speed are also provided.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1615-1622
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• 2016

This research aims to develop a voyage performance monitoring system based on international standards. The developed system is equipped with an electronic navigational chart(ENC) that provides onshore and offshore information, as well as supports standardized interfaces with navigational equipment, such as a gyro compass, a differential global positioning system(DGPS), and an automatic identification system(AIS), to monitor the navigation route in real time. In addition, the proposed system adopts a car navigation system to provide a graphical user interface, an intuitive menu-driven configuration, and an easy guide for safer sea navigation. The system, interfaced with the gyro compass and DGPS, was verified without any data loss, and passed a test conducted under extreme conditions by the Korea Laboratory Accreditation Scheme(KOLAS). Finally, the system contributes to preventing collision of vessels and minimizing casualties by maximizing the convenience of mariners which a conventional system does not provide.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.587-592
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• 2016

Bellows for LNG carriers must be corrosion resistant in order to operate in seawater environments. They must also have long fatigue lives in order to withstand the expansion and contraction caused by large temperature changes and continuous vibration in extreme environments. In order to incorporate these properties into bellow design, it is important to use materials that are resistant to cold brittleness and corrosion, and maintain their optimized forming condition. The design conditions and forming methods used for bellows must be optimized in order to incorporate these characteristics. In this study, finite element analysis was used to develop cryogenic bellows, which have good mechanical strength and reliability. In addition, two different forming methods (mechanical and hydroforming) were used to design and produce bellows, in order to derive their forming condition. The height, thickness, and hardness of the convolutions of bellows produced by each method were measured and compared with each other. The results confirmed that the two forming methods produced bellows with different mechanical properties.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.2
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• pp.129-136
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• 2016

Floating offshore structures keep its position by a mooring system against various kind of environmental loadings. For this reason, a reliable design of the mooring system is a key factor for initial design stage of a floating structure. However, there exists possibility of mooring failure, even the system is designed with enough safety margin, due to the unexpected extreme environmental conditions or long-term fatigue loadings. The breaking of one of the mooring lines may change the tension level of the other mooring lines, which can potentially result in a progressive failure of the entire structure. In this study, time domain numerical simulation of 10MW class wind-wave hybrid platform was carried out with partially broken mooring line. Overall platform responses and variations of the mooring line tension were numerically evaluated.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.1
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• pp.77-84
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• 2022

A submarine power cable is a transmission cable for carrying electric power below the surface of the water. Recently, submarine cables transfer power from offshore renewable energy schemes to shore, e.g. wind, wave and tidal systems, and these cables are either buried in the seabed or lie on the ocean floor, depending on their location. Since these power cables are used in the extreme environments, they are made to withstand in harsh conditions and temperatures, and strong currents. However, undersea conditions are severe enough to cause all sorts of damage to offshore cables, these conditions result in cable faults that disrupt power transmission. In this paper, we explore the design criteria for such cables and the procedures and challenges of installation, and cable transfer splicing system. The specification of submarine cable designed with 3 circuits of 154kV which is composed of the existing single circuit and new double circuits, and power capacity of 100MVA per cable line. The determination of new submarine cable burial depth and cable arrangement method with both existing and new cables are studied. We have calculated the permission values of cable power capacity for underground route, the values show the over 100MW per cable line.