• 대한기계학회논문집
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• 제19권3호
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• pp.661-669
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• 1995

This paper presents a design method of dynamic positioning control system in view ofpractical design concept for reliability and robust realization. This method adopts a design method of multivariable robust servo system. The practical experiments of the dynamic positioning control were carried out for a semi-submersible 2-lower hull type platform model with 4 rotatable thrusters in a small water tank. The results fo overall experiment show that the proposed position control method will be an efficient method to the better control performance of dynamic positioning system under serere environment and it is substentially practicable for the platform.

• 한국해양공학회지
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• 제11권4호
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• pp.76-89
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• 1997

The hydrodynamic interaction characteristics between multiple floating bodies of semisubmersible type are examined to present the basic data for the design of huge offshore structures supported by a large number of the floating bodies in multi-directional irregular waves. The numerical approach is based on a combination of a three-dimensional source distribution method, the wave interaction theory and the spectral analysis method. The effects of wave directionality on the wave exciting forces acting on multiple floating bodies in multi-directional irregular waves also have been pointed out.

• 한국해양공학회지
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• 제2권1호
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• pp.59-70
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• 1988

This paper presents the results of motion tests of a moored semi-submersible platform in regular waves. To investigate the effects of mooring system on the motion characteristics, the tests were performed under the various mooring conditions in regular head and beam waves. Two types of mooring system were employed: one is composed of soft springs and the other is of chains. In the case of chains the pretensions were varied to investigate the dynamic effects of mooring forces as well as the motion responses of the semi-submersible. The motion responses and mooring tensions were measured and analyzed by the double amplitude method. The measured motion responses were also compared with the results of calculation from three-dimensional potential theory. Finally, the dynamic behaviors of mooring chains were studied.

• 한국해양공학회지
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• 제28권4호
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• pp.274-279
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• 2014

This paper investigates the line dynamic forces connecting tugs and a floater, where the planar motion of the floater is due to the weather criteria during the position keeping of the offshore structure by tugs. The analysis situation consists of the position keeping states for the seabed mooring line connection work of the offshore structure at the offshore site. Specifically, the decision about the tug power capacity for the position keeping is essential and depends on the weather criteria, line characteristics, length of line, etc. The planar motion of the structure is constrained by the interference of the installation vessel's operational range, behavior of the underwater fairlead, and other surrounding structures. In this paper, the tug line forces and planar motion of an offshore structure are summarized dependent on the tug line length and line material characteristics in the states fora given floater draft and weather criteria. The tug line dynamic forces and planar motion evaluated here will be used to determine the proper tug power and clearance of an offshore structure.

• 한국해양공학회지
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• 제28권1호
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• pp.6-11
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• 2014

This paper presents the results of an experimental study of wave run-ups on a semi-submersible offshore structure. A series of model tests with a 1:80 scale ratio were carried out in the two-dimensional wave basin of MOERI/KIOST. The experimental model had two columns and one pontoon. The model was fixed and wave elevations were measured at five points per column. Two different draft (operational & survival) conditions and three wave heights were considered under regular wave conditions. First, the nonlinear characteristics of wave run-ups are discussed by using the time series data. Then, the wave heights are compared with numerical results based on the potential flow model. The comparison shows fairly good correlation between the experiments and computations. Finally, wave run-ups under the operational and survival conditions are suggested.

• 한국해양공학회지
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• 제27권1호
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• pp.9-15
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• 2013

This paper calculates the mating dynamic forces of a semi-submersible offshore structure's topside module, where a hull moored in the sea is combined with a topside module carried by a heavy lift vessel, as a mating installation method. The environmental conditions include various wave directions and wave heights, with constant wind and current speeds. Appropriate ballast and de-ballast plans for the heavy lift vessel and hull of the semi-rig should be performed in order to safely obtain these forces, whereas a fixed platform or the GBS (Gravity based structure) type of offshore structure only needs a ballast plan for the heavy lift vessel. From this paper, the allowable wave height or wave direction for the mating procedure can be investigated based on the standard DAF (Dynamic amplitude factor) of the rules and regulations.

• 대한조선학회논문집
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• 제50권3호
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• pp.129-137
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• 2013

Each owner or operator of offshore products uses a maintenance management system like CMMS(Computerized Maintenance Management System) in order to manage their assets effectively and efficiently for a long time. But most of maintenance management systems have been focused on machinery items, not on 'Hull' until now. On the other hand, classifications like ABS, DNV, GL are having a sale on hull inspection and maintenance system for ships and an interest in hull maintenance system is increasing because of the application of EDD(Extended Dry Docking). This paper discusses the concept, inspection process and the practical application of Hull maintenance for Semi-submersible drilling rig to extend the service life and run a stable operation.

• 한국해양공학회지
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• 제32권3호
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• pp.177-183
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• 2018

This study simulated ice load and the motion response of a moored semi-submersible rig in pack-ice conditions using a finite element method. Ice flows of random size and shape were modeled, and interactions for ice-sea, ice-structure, ice-ice were simulated using a simplified method. Parameters for the simplified method such as drag force coefficient and the pressure-penetration relation were obtained based on the result of detailed analysis using the coupled Eulerian-Lagrangian method. The mooring lines were modeled by spring elements based on their stiffness. As a result of the simulation over 1,400 seconds, the force and motion response of the rig were obtained and validated using discrete elements and compared with the results found by the Krylov State Research Centre.

• 대한조선학회논문집
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• 제53권1호
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• pp.1-9
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• 2016

It is important to research and understand the physical phenomenon around a semi-submersible offshore structure on waves and currents because the wave run-up and load occurs owing to the waves and currents. In this study, the numerical simulations are performed about flow around a fixed semi-submersible offshore structure. The Modified Marker-density method is adopted in the present computation procedure, this method is one of the various methods to define the free-surface. The present computation results are compared with existing experimental and numerical simulation(VOF method) results. And, the computation results are relatively coincident with the existing results of model test and numerical simulation by VOF method.

• 한국해양환경ㆍ에너지학회지
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• 제18권3호
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• pp.223-232
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• 2015

본 연구에서는 부유식 파력-해상풍력 연계형 발전시스템의 기반구조물 개념설계에 대한 내용을 다루고 있다. 세계적으로 해양 신재생에너지에 대한 관심이 커져가고 있다. 파력과 해상풍력은 다른 해양에너지원과 더불어 주요 관심이 되는 에너지원으로서 발전적지가 대체로 일치한다는 특징이 있다. 따라서 파력과 해상풍력을 복합하여 발전하는 시스템은 경제적으로 많은 이점이 있고 이미 여러 나라에서 파력-해상풍력 복합발전 시스템을 개발하고 있다. 이에 따라 우리나라에서도 10MW급의 파력-해상풍력 복합발전 시스템을 개발하기 위한 연구가 수행되었다. 본 연구에서는 다수 풍력발전기와 파력발전기의 배치를 고려하여 반잠수식 구조물이 설계되었다. 또한 설치해역의 환경을 고려하여 계류시스템과 파워케이블이 설계되었다. 본 논문에서는 이러한 복합발전 플랫폼의 개념설계 결과를 제시하고 다양한 발전시스템의 배치를 고려한 설계상의 어려움을 토의하고 설계 방법을 제시한다.