• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.04a
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• pp.284-291
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• 1999

The reliability analysis is of great importance in their design since offshore towers are high-cost and high-risk structures. The design of platforms in the marine environment depends on results of the dynamic behavior of the structure during earthquakes and storm wave conditions. this paper presents results of an analytical study on evaluating dynamic response of steel jacket modelled by space frame elements. program $\boxDr$OFSPC$\boxUl$for the linear and nonlinear dynamic analysis of steel jacket platform has been developed using FORTRAN 90 programing language through the present study. Free vibration and dynamic behavior of steel jackets under regular and irregular wave and earthquake force are investigated using this program

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.495-508
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• 1999

변형된 라이저의 단위 접선벡터상의 운동학적 제약조건을 적용하여 심해저 라이저의 비선형 동적해석을 행한다. 이 조건의 적용으로 자유도수를 감소시킬 수 있으며 심한 비선형성으로 인한 해의 발산 가능성을 제거할 수 있다. 라이저의 거대변형으로 인한 기하학적 비선형성과 비선형 경계조건이 고려된다. 또한, 비선형성이 포함되는 수동학적 하중이 조류와 파랑에 의해 발생하여 내부에 정상류가 흐르는 라이저관의 외벽에 작용하게 된다. 이 외에도라이저 자체의 축방향 변형조건을 고려한다. Galerkin의 유한요소 근사화와 시간증분자를 적용하여 유한요소에 대한 평형 메트릭스 방정식을 유도하고, 수치해석을 위한 알고리즘을 제안하며 API 보고서의 결과와 비교함으로써 제안된 모델이 검증된다. 또한, 기하학적 비선형성으로 인한 영향을 조사하였다.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.75-84
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• 1997

The up-to-date fatigue strength assessment system for ship structures was developed based on the spectral analysis method and numerical calculation for a membrane type LNG carrier was carried out to verify the effectiveness of the developed system. The wave induced loads acting on the ship's hull were calculated based on strip theory. And introducing the concept of influence factor and 3-D fine mesh structural analysis, direct calculation of long-term distribution of wave induced stress components was realized. Using the derived long term distribution of stress components and Miner-Parmgren's linear damage accumulation rule, fatigue strength of structural components were investigated.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.2
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• pp.132-140
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• 1993

The design of LNG ship needs very high level structural design/analysis technology compared with conventional ship types because it requires perfect security against the extremly dangerous and cryogenic cargo. Hence, present paper describes the general procedure of the structural safety assessment for independent tank type LNG ship, which contains following items. 1) Long term prediction of the wave induced stresses including ship motion analysis, structural analysis of hull and tank and stochastic analysis process of ocean waves. 2) Fatigue strength analysis of a tank structure based on the S-N approach. 3) Structural safety assessment against the fatigue crack propagation based on the LBF(Leak Before Failure) concept. The first report focuced on the item (1) (2) and example calculation was performed on a prototype LNG ship. The remained part will be covered by the second report.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.4
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• pp.307-316
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• 2002

In order to evaluate the deformation and stiffness of frame structure for fishery, composed of unit platforms which made of two concentric high density polyethylene buoys fixed by clamps and belts and rubber hinge components, under wave, the structural analysis for the square type of the structure was carried out by using finite element methods. The accurate physical properties of rubber hinge components determined by material tests were an important parameter to evaluate more reliable structural stability for the structure. The idealization to beam element with equivalent stiffness and rubber element with linearity for rubber hinges was necessary for the modeling of rubber component which has hyper-elastic characteristics. In addition, it was shown that the structural response of the structure under wave was larger in the hogging condition than that of in the still water or in the sagging condition.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.94-98
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• 2003

Remotely Operated Vehicle. ROV is a new concept equipment being made to replace the manned systems for investigating the deep sea environment. This paper presents the dynamic cable response during ROV launching considering the coupling effects of ship motion. By the harmonic response analysis, the variations of cable tensions were obtained. Harmonic forces in head/beam sea states were calculated by the concept of relative acceleration which obtained by ship motion analysis.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.152-161
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• 1990

In this paper, a hybrid element method(HEM) for the evaluation of the hydrodynamic responses of arbitrary-shaped offshore structures is studied. The hydrodynamic pressure forces are assumed to be inertially dominated, and viscous effects are neglected. The mathematical formulation procedure of the hybrid element method with the analytical eigenseries solution is established systematically. The computer program based on the HEM has been developed, and applied to solving the wave diffraction and radiation problems for arbitrary shaped structures. From comparisons of the results obtained by using the other avaliable solution methods, the method for the evaluation of the hydrodynamic forces using the HEM and the computer program developed here have been proved to be valid.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.37-43
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• 1995

The procedure and the results of the full scale strain measurement of the long-range high-speed foil catamaran are described. The wave induced stresses at the center struts of the foils were measured during the sea trials in order to evaluate the hydrodynamic force acting on the foils and to verify the structural safety of the foil structures. From the statistical properties of the measured response of the stress, the most probable maximum values of the lift force and the stresses at the foils in service life of the ship are predicted and compared with the design parameters of the foils which were applied in the design of the subject ship. The available prediction processes of the measured stress are studied and the results of the applied processes are compared with each other.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.2
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• pp.1-9
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• 1985

Two methods for the dynamic analysis of fixed offshore structures subjected to random waves are studied. They are the frequency domain method using the equivalent linearization of the nonlinear drag force, and the time domain method utilizing the Monte Carlo simulation technique for time series of random wave particle velocities and accelerations. Example analyses are carried out for two structures with different structural characteristics and for various wave conditions. A comparison has been made between the results obtained by two methods.

• Journal of Ocean Engineering and Technology
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• v.19 no.4 s.65
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• pp.1-8
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• 2005

A nonlinear time-domain strip theory for vertical wave loads and ship responses is to be investigated. The hydrodynamic memory effect is approximated by a higher order differential equation without convolution. The ship is modeled as a non-uniform Timoshenko beam. Numerical calculations are presented for the S175 Containership translating with the forward speed in regular waves. The approach described in this paper can be used in evaluating ship motions and wave loads in extreme wave conditions and validating nonlinear phenomena in ship design.