• 한국수산과학회지
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• 제34권6호
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• pp.661-665
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• 2001

해상가두리의 안정성 및 기능성 향상을 위한 최적 계류시스템을 개발하기 위하여 천해역에 적합한 계류시스템을 검토하여 유연부 이 계류시스템을 선정하였다. 이를 위한 해석프로그램을 정립하고, 수리모형실험 결과와 비교하였다. 해석프로그램의 타당성을 확인 한 후, 적용할 만한 계류시스템을 구성하고 수치계산을 통하여 해상가두리를 위한 적정 계류시스템을 제시하였다. 해상가두리의 계류시스템은 유연부이 계류시스템이 권장되며, 계류배치는 탁월 외력환경과 일치하는 방향으로 하고, 수평계류삭인 나일론 로프는 해상가두리 길이의 0.5배 이상, 경사 와이어 로프는 수심의 2배 이상이 바람직한 것으로 나타났다. 또한, 중간부 이의 증설은 계류장력 및 표류변위를 감소시키는 효과를 가질 것으로 판단된다. 차후, 해상가두리의 동적응답 특성을 계류시스템 해석모델의 개발과 계류시스템의 설계가 요구된다.

• 한국전산구조공학회논문집
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• 제19권1호
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• pp.105-111
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• 2006

돌핀계류시스템은 부유식 해양구조물의 계류장치로서 강도 및 유용도 관점에서 바람직한 대안이 될 수 있다. 돌핀계류시스템 설계과정에서 정확한 파력산정과 필요한 지지파일의 개수선정은 주요 설계요인이 된다 본 논문에서는 파의 충격하중을 포함한 외력에 대한 구조해석을 통하여 적정한 돌핀시스템의 설계과정과 형식을 제시하였다. 부유식 해양구조물을 위한 돌핀계류시스템의 경우 다수의 지지파일시스템보다 단주의 지지파일시스템이 설계관점에서, 제한적이기는 하나, 유용성이 높다는 점을 알 수 있었다.

• 대한조선학회논문집
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• 제53권5호
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• pp.435-446
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• 2016

In this study, hydrodynamic and mooring analysis for LNG FSRU moored by an internal turret with 9 mooring lines are numerically performed using commercial softwares, Hydrostar and Ariane. Met-ocean combinations for screening method are taken from wave governed condition(BV Rule Note NR 493) with relative heading between wave and wind between −45° and +45° and relative heading between wind and current between −30° and +30°. Extreme mooring analysis and sensitivity analysis are performed for intact and damaged (=one line missing) conditions and the parameters for sensitivity analysis are wave peak period, peak enhancement factor and line pretension. In the viewpoint of the design tension in mooring line, chain diameter is designed to satisfy safety factor for each conditions. As the chain diameter is increased from 152mm to 171mm, the designtension is reduced while the minimum breaking load is increased.

• 한국해양공학회지
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• 제31권4호
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• pp.299-307
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• 2017

The design of the mooring line to maintain the position of an offshore structure in rough marine environments is recognized as a very important consideration. Conventional fatigue evaluation of a mooring line was performed by considering the tensile force acting on the mooring line, but the mooring line broke after 238 days in the girassol area even though the expected fatigue life was expected to be longer. The causes of this event are known to be due to OPB/IPB (out-of-plane bending/in-plane bending) caused by chain link friction due to the excessive tensile strength of the mooring line. In this study, three models with different boundary conditions were proposed for fatigue analysis of a mooring line considering OPB/IPB. Interlink stiffness was calculated by nonlinear structure analysis and a stress concentration factor was derived. In addition, the sensitivity of interlink stiffness according to the magnitude of tensile force, large deformation effect, and coefficient of friction was analyzed, and the effect of critical elastic slip and bending moment calculation position on interlink stiffness was confirmed.

• 동력기계공학회지
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• 제17권3호
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• pp.89-98
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• 2013

In this paper, the authors consider control system design problem of barge type surface vessel. It is based on the Dynamic Positioning System(DPS) design problem. The main role of barge ship is to carry and supply the materials to the floating units and other places. To carry out this job, it should be positioned in the specified area. Even though sometimes the thrust systems are installed on it, in general the mooring winch system with the rope is used. It may be difficult to compare the control performances of two types. But, if we consider this problem in point of usefulness, we can easily find out that the winch control system is more useful and applicable to the real field than the thrust control system except a special use. Therefore, in this paper we consider a single type mooring winch system and control system design problem in which accurate position control is needed. Because this result can be extended to the general type mooring system in which a number of winch are installed. At first, a mathematical model of winch is obtained and evaluated to verify the usefulness for control system design by experiment. Also, the disturbance model is extracted from experiment data to evaluate the strength of the uncertainty. Based on this results, the robust control system is designed and control performance is evaluated by simulation.

• 대한조선학회논문집
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• 제40권1호
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• pp.20-27
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• 2003

The FPSO is moored by mooring lines to keep the position of it. The nonlinear motion analysis of the moored FPSO must be carried out in the initial design stage because sea environments affect motion of it. In this paper, the mathematical model is based on the slow motion maneuvering equations in the horizontal plane considering wave, current and wind forces. The direct integration method is employed to estimate wave loads. The current forces are calculated by using mathematical model of MMG. The turret mooring forces are quasi-statically evaluated by using the catenary equation. The coefficients of a model for wind forces are calculated from Isherwood's experimental data and the variation of wind speed is estimated by wind spectrum according to the guidelines of API-RP2A. The nonlinear motions of FPSO are simulated under external forces due to wave, current, wind including mooring forces in time domain.

• 대한조선학회논문집
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• 제54권2호
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• pp.151-160
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• 2017

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

• 대한조선학회 특별논문집
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• 대한조선학회 2013년도 특별논문집
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• pp.97-102
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• 2013

As the offshore oil and gas upstream industry moves into deeper water, the FPSOs are the cost-effective solution. In the harsh environment such as in North Sea, station keeping and heading control capability obtained through the DP and Position Mooring (DPM) system of FPSOs play important roles to keep the safety. This paper introduces the concept, function and sub-system of the DPM systems which has been applied for the North Sea FPSOs since the late 1980s. The requirements and guidelines of some internationally recognized standards are also described, which are important to build the design basis at the early phases of the project.

• 한국해양공학회지
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• 제23권1호
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• pp.89-95
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• 2009

The purpose of the present study was to evaluate the safety under extreme environmental conditions and the dynamic safety under service environment conditions, of oceanographic buoy mooring systems consisting of a variety of materials, including chain, wire rope, nylon rope, and polypropylene rope. For the static safety assessment of a mooring system, after the calculation of external forces and the division of a mooring system into finite elements, the numerical integral was conducted to yield the elemental static tension until satisfying the geometrical convergence condition. To evaluate the dynamic safety, various processes were considered, including data collection about the anticipated areas for mooring, a determination of the parameters for the interpretation, the interpretation of the dynamic characteristics based on an analytic equation that takes into account the heave motion effect of a buoy hull and a mooring system, and a fatigue analysis of the linear cumulative damage. Based on the analysis results, a supplementary proposal for a wire rope that has a fracture in an actual mooring area was established.

• 한국지반공학회논문집
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• 제22권9호
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• pp.15-22
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• 2006

선박을 정착시키기 위하여 해저지반에 관입된 드래그 / 영구앵커와 앵커에 연결된 닻줄의 지지력 및 변형을 해석하여, 기존의 앵커와 닻줄의 분석 및 개발을 위하여 만들어진 해석프로그램을 calibration 하기 위하여 원심모형시험기를 사용한 시험을 하였다. 시험에 사용된 닻줄은 ball chain 및 wire cable로써, 일정한 단면을 가지고 있으며, 해성점토 지반 안에 다양한 깊이로 정착시킨 후 원심모형시험을 실시하였다. 현장응력조건을 모사하기 위하여, 미리 응력을 가한 시험용 닻줄에 단계별 가속을 하였다. 이 논문은 닻줄의 해석을 위한 중요한 두 가지 변수인 닻줄과 지반의 부착력 및 접착면적환산계수를 결정하기 위한 과정을 설명하고자 하였으며, 이로 인한 닻줄의 변형 및 지지력 변화를 규명하였다.