• Journal of Navigation and Port Research
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• v.33 no.5
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• pp.315-321
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• 2009

The Very Large Marine Structure has been widely used new method of ocean space instead of method for reclamation Therefore, VLFS is proposed to coincide on such request. It can be established regardless of nature of soil and height of water, and stream of flow exists under the floating structure, there is seldom effect in natural environment. Fuertherrnore, it can do easily to do assembly and taking to pieces due to expansion or removal. Based on the regulation by class, VLFS have to possess more than enough structural strength against severe wave loading induced by green sea condition Therefore, There are performed structural simulation as well as experimental test about expected loading scenario in order to examine the safety of structure. Up to now, various examinations based on the strength limit value of the main structural material have been done based on the elasticity response analysis. However, there is little finding about the collapse behavior and the safety when the load that exceeds the collapse of the material acts. In the present study, we investigated the collapse behavior based on the ultimate limit state calculated by FE-analysis.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.75-81
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• 2000

Very large floating structures have rather small motion characteristics except their ends, where the motions become much larger due to the elastic motion of the structure. This paper presents the numerical predictions of hydroelastic behaviors of VLFS in irregular waves. To predict motion responses of structure in irregular waves, the source-dipole distribution method and finite element method is used.

• Journal of Navigation and Port Research
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• v.26 no.4
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• pp.441-447
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• 2002

The importance of utilization of ocean space is increased due to high population and narrow land space. The development of a new technology for future use of ocean space, such as a design technology of Very Large Floating Structures(VLFS) is needed. This paper introduces the rime history analysis of superstructures on very large floating structures and proposes the estimation method of time displacement history considering wave loads. The dynamic responses of superstructure according to variation of period and amplitude are analysed using an example frame structure and the dynamic structural safety of VLFS pilot superstructure is evaluated.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.66-74
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• 2000

In this paper, hydroelastic responses of the very large floating structure are studied based on the linear potential theory. A theoretical method is developed to analyze the hydroelastic reponses of very large floating structures(VLFS) using the pressure distribution method and the modal expansion method. The singularities distributed on a zero draft plate at the free surfaces and hydrodynamic pressures are evaluated. The deflections of structure are expanded approximately in terms of natural mode functions of free-free beam. The calculated items are pressure distributions. vertical motions, hydrodynamic coefficients and bending moments of VLFS. The numerical results are compared with those measured by experiments.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.90-103
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• 1997

A numerical procedure is described for predicting the motion and structural responses of the very large floating offshore structures supported by multiple 3-D floating bodies of arbitrary shape in multi-directional irregular waves. The developed numerical approach taking into account of the hydrodynamic interactions among the multiple floating bodies is based on a combination of the 3-D source distribution method, the wave interaction theory, the finite element method and the spectral analysis method to get the significant values of the dynamic responses in the multi-directional irregular waves. The effects of wave interactions and directionality on the dynamic responses of a very large offshore structure, which is semisubmersible ring type, are numerically examined.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.63-68
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• 2000

A very large floating structure has rather small motion characteristics as to the whole body, while the motion at end part of such structure becomes largest due to the elastic motion of the structure. This paper presents on the theoretical result on the relative motion characteristics and green water phenomena of VLFS in waves This phenomena affect not only to strength of the structure but also the determination of depth of structure. To predict motion responses of structure in regular waves, the source-dipole distribution method and F.E.M is used By irregular wave results, the probability of occurrence of green water and response of the structure were calculated.

• Journal of Ocean Engineering and Technology
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• v.16 no.1
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• pp.71-75
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• 2002

대형 시추구조물의 건조는 보통 드라이도크에서 하거나, 해양에서 선체와 데크를 접합하는 방법을 사용한다. 그러나 적당한 해양 접합장소가 없거나 드라이도크의 공간부족으로 현대중공업에서는 드라이도크나 해양에서의 접합건조 대신 부유식 시추구조물을 지상에서 조립하는 방법을 채택하게 되었다. 현대중공업에서는 세 가지 단계를 통해 지상 데크조립을 수행하였다. 첫 번째는 네 개의 철골구조 리프팅타워 상에서 유압리프팅시스템을 이용하여 데크를 지상으로부터 38m 들어올린다. 두 번째는 마찰을 줄이기 위해 윤활제가 칠해진 합성 플라스틱으로 싸인 미끄럼틀(Skidway)을 이용하여 두 개의 6000톤 짜리 하부구조를 데크 아래로 끌어 들인다. 마지막 단계로 데크와 하부구조를 단단히 결합시킨다. 이 과정에 2주일이 소요되었으며 일련의 작업을 거쳐 중량 25,500톤급의 Deepwater Nautilus (RBS-8M) 시추선을 무사히 바다 위로 인도하였다. RBS-8M의 데크결합에 Super Lift를 적용하여 성공시킨 사례를 통해 현대중공업의 초대형 시추구조물 건조방식이 이상적이고, 작업 공기나 원가 측면에서 우위가 있음을 시사하고 있으며 이렇게 건조작업의 대부분을 지상에서 수행한 과정을 통해 작업관리, 품질관리, 일정관리에도 좋은 결과를 가져올 수 있었다.

• Cement Symposium
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• no.30
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• pp.75-79
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• 2003

• Journal of the Society of Naval Architects of Korea
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• v.36 no.4
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• pp.64-76
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• 1999

In this paper hydroelastic experimental techniques of very large floating offshore structures are suggested based on the model test carried out in the UOU Ocean Engineering Wide Tank. The prototype is a box-shaped floating structure with length of 300m, breadth of 60m, depth of 2m and draft of 0.5m and longitudinal bending rigidity as $4.87{\times}10^{10}kgm^2$. The scale ratio is 1/42.857. The model is realized by aluminum square pipes with the section dimension of $20mm{\times}20mm$. The numbers of longitudinal and transverse pipes are 7 and 35 respectively. Heave motions at selected points are measured with potentiometers and bending moments with strain gages.

• Journal of Ocean Engineering and Technology
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• v.15 no.1
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• pp.26-30
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• 2001

Up to now, Most studies of hydroelasticity are about frequency domain analysis. Those aren't suited for analysis of the landing take-off, and dropping of aircraft on a structure. So, the concern of this paper is the transient behavior of a VLFS subjected to dynamic load, induced by airplane landing and take-off. To predict the added mass, damping coefficient, and wave exciting force, the source-dipole distribution method was used in the frequency domain. The responses are accomplished by using the FEM scheme. A time domain analysis method is based on the Newmark β method to pursue the time step procedure, taking advantage of memory effect function for hydrodynamic effects.