• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.551-555
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• 2009

This study analyzed the cause for mooring chain cut in a naval ship moored, in preparation for a typhoon approach, to a buoy in a shelter. The result of the analysis led to a very interesting fact. That is, while officers usually understood the cut results from the fact that the wind and the tide were stronger than what the mooring chain can hold, according to the study, it was analyzed the impact power at the point where the mooring chain and the ship's body met was a main factor in the cut. Also, it was confirmed that the analytic result of the study is more logical from the point of mathematical analysis and that the cut corresponds to what the then-witnesses stated about the situation.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.99-110
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• 2017

This paper presents the study of the bending behavior of mooring chain links for keeping the position of the offshore floating structures. In general, chain links have been thought as the axial members due to the fundamental boundary condition. But, the flexural stiffness can be induced to the contact surface between chain links when friction occurs at the surface of the chain links due to high tensile force. Especially, the mooring chains for offshore floating platforms are highly tensioned. If the floater suffers rotational motion and the mooring chain links are highly tensioned, the rotation between contact links, induced by the floater rotation, generates the bending moment and relevant stresses due to the unexpected bending stiffness. In 2005, the mooring chain links for the Girassol Buoy Platform were failed after just 5 months after facility installation, and the accident investigation research concluded the chain failure was mainly caused by the fatigue due to the unexpected bending stress fluctuation. This study investigates the pattern of the induced bending stiffness and stresses of the highly tensioned chain links by nonlinear finite element analysis.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.3
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• pp.184-191
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• 2011

Preliminary design of a mooring system for a floating wave energy converter(WEC) is performed. A mooring line is designed to consist of two parts; the one is a chain in heavy weight laid on the seabed and linked to an anchor on the seabed and the other is a light weight chain suspended at a floater. A high weight chain laid on the seabed can contribute to mitigate dynamic energy propagated from top oscillation and decrease anchor weight and volume. Through a low weight chain suspended between a floater and seabed the WEC's function to produce energy from wave can be affected in minimum by the motion of a chain. The static and dynamic analyses for the designed mooring system were carried out to evaluate WEC system's safety. The present study shows that the designed gravity anchor moves horizontally due to the tension exerted on the anchor in the severe ocean environmental condition. The present mooring system should be redesigned to satisfy the safety requirements. The present study will be useful to predict the safety of the mooring system under ocean environment.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.4
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• pp.185-191
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• 2004

A mooring system can be applied to keep the position of a floating structures. In this study, the structural analysis is carried out to analyze the dynamic characteristics of a mooring line for a floating breakwater. A three-dimensional equations of motion for a submerged chain are derived. Bending stiffness is considered for the necessary restoring force in the regions of zero tension. A fortran program is to be developed by employing finite difference method. In the algorithm, an implicit time integration and Newton-Raphson iteration are adopted. The results of simulation show good agreement in tension response pattern with the experimental results of a reference. The results of this study can contribute for the design of mooring system for a floating breakwater.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.144-147
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• 2002

오탁방지막은 해상이나 하천에서 준설 및 매립공사등으로 인한 부유사 확산을 방지하는 막체구조로서 부력이 우수한 Polystyrene계로 원통형 부체를 이루는 부체부, 고장력 합성섬유를 사용하여 외력에 대하여 저항하고 여과기능이 있는 막체부,그리고 막체부의 이동을 막기 위해 해저면에 고정시키는 계류라인(Mooring Line) 및 블록(Anchor Block)부로 이루어져 있다 특히 계류라인은 와이어로프 또는 체인 등으로 부체부와 앵커블럭을 연결시켜 주는 역할을 한다. (중략)

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.403-406
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• 2013

표준형 부표류 계류시설 기술개발계획 승인(2010. 6. 29) 후 중소기업청 구매조건부 신제품 개발사업의 일환으로 표준형 부표류 계류시설 기술개발이 2010. 6. 1~2012. 5. 31. 약 24개월간 추진되었고, 2013. 5. 31. 신제품 기술개발사업 최종 "성공" 평가로 판정됨에 따라 (등)부표 계류 안정성 검토 결과를 반영한 현장 활용을 통해 신(新) 계류시설의 제도적 기틀을 마련하게 되었다. 그동안 주강용 체인의 문제점으로 지적되었던 고중량, 부식성, 마모성, 해양환경, 전량수입 등과 같은 관리 운영상 문제점이 개선되고, 연구개발(R&D)를 통한 해양분야의 창조경제 실현이 기대된다.

• The Journal of Korean Institute of Information Technology
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• v.16 no.12
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• pp.41-47
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• 2018

The buoy-enabled underwater surveillance system is a device that is installed in a particular sea area and operated for a certain period of tine and moved to another sea area after recovery. In this paper, a mooring method which is applied for a buoy-enabled underwater surveillance system was selected to maintain installation and enure stable operation. Also, the structure of the mooring line was designed. Two-point mooring method was selected considering interference with the communication cable of array-assembly. The composite structure of buoy chain, nylon rope, and anchor chain is designed as the basic component of mooring line. For the verification of design, a numerical simulation and wave tank experiment were performed. Their results were confirmed similarity in test condition. Finally, the mooring lines were designed for the environment of the sea trial location. The mooring line produced by the final design confirmed the stability above the significant wave height considered in the design on the sea trial.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.195-201
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• 2001

The time simulation of slow drift motions of moored FPSO in waves is presented. The equation of motion based on Cummin's theory of impulse responses are employed, and are consisted of horizontal plane motions such as surge, sway and yaw. The added mass, wave damping coefficients, first order wave exciting forces and the second order wave drift forces involved in the equations are obtained from three-dimensional panel method in the frequency domain. The mooring lines are modeled as quasi-static catenary cable. As a numerical example, time domain analyses are carried out for a box-type FPSO in long crest irregular wave condition.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.2109-2112
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• 2007

독도는 울릉도에서도 동남쪽으로 약 87.4km 떨어져 외해의 영향을 많이 받고 있는 지역이지만 방파제 등 외곽시설이 전무하여 평상파랑에도 접안이 어려운 경우가 많아서 독도 관광자원 활용도 및 편의시설 제공면에서 많은 어려움이 있다. 이에 본 연구에서는 독도 접안시설의 전면에 최근 국내에 본격적으로 도입되고 있는 부방파제(floating breakwater)를 설치할 경우 고정식 방파제 설치에 따른 문제점을 충분히 개선할 수 있다고 판단하여, 부방파제 설치에 따른 기술적인 타당성과 부두 이용률 개선효과 등을 연구 하였다. 독도의 접안시설은 해역이 동도와 서도에 의해 북쪽은 일부 차폐되고 남쪽은 직접 노출되어 있는 지리적 특성이 있어 주 파향인 남쪽계열의 8개 파향(SE, SSE, S, SW, SSW, WSW, W, WNW)의 평상파 제어가 가능하도록 방파제를 배치하였고, 이에 따른 부두 이용률 검토결과 부방파제를 설치할 경우 남쪽계열 파랑에 대하여 현상태에 비하여 부두 이용률이 대략 2배정도 증가되는 것으로 나타났으며, 부방파제 계류시스템의 안정에 대해서도 부체에 영향을 주는 외력에 대하여 계류체인의 길이와 Anchor Block 자중의 규모를 적당히 조정하면 충분히 안정한 것으로 검토되었다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.2
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• pp.248-253
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• 2023

Most offshore platforms utilize chain mooring systems for position keeping. However, information regarding related design modification processes is scarce in literature. This study focuses on the floating liquefied natural gas (LNG) bunkering terminal (FLBT) as the target of shore platform and analyzes the corresponding initial mooring design and model tests via numerical simulations. Subsequently, based on the modified design conditions, a new mooring system design is proposed. Adjusting the main direction of the mooring line bundle according to the dominant environmental direction is found to significantly reduce the mooring design load. Even turret-moored offshore platforms are exposed to beam sea conditions, leading to high mooring tension due to motions in beam sea conditions. Collinear environmental conditions cannot be considered as design conditions. Mooring design loads occur under complex conditions of wind, waves, and currents in different environmental directions. Therefore, it is essential appropriately assign the roll damping coefficients during mooring analysis because the roll has a significant effect on mooring tension.