• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.6
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• pp.357-364
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• 2013

In previous study, the hybrid floating structure composed of a pontoon and a semi-submersible was suggested to reduce the motions of floating structure. It was reported that the suggested hybrid floating structure could reduce the motions. However, the hybrid floating structure could not support enough buoyancy. In this study, the combination floating structure is newly suggested to resolve the problem. In order to adopt the shape of floating structures reducing the motions, the hydrodynamic analysis of various floating structures such as the pontoon, the hybrid and the combination of floating structure is carried out through hydrodynamic analysis program ANSYS AQWA. It is found that the combination floating structure is remarkably effective to reduce the motions compared to the other cases. Thus, the suggested combination floating structure may be a useful offshore structure for constructing a very large floating structure.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.4 s.142
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• pp.357-367
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• 2005

A numerical method is developed for the hydroelastic response of the Very Large Floating Structure considering the sea-bottom topography. The sea-bottom effects on the hydroelastic response of the floating structure is studied. The sea-bottom topography should be considered when the floating structure is constructed near the shore. To investigate the sea-bottom effects, four different sea-bottom topographies are considered in this study. finite-element method based on the variational formulation is used in the fluid domain, The pontoon-type floating structure is modeled as the Kirchhoff plate. The mode superposition method is adopted for the hydroelastic behavior of the floating structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5B
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• pp.313-320
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• 2012

A hybrid floating structure system combined with pontoon and semi-submersible type modules is proposed. This new system can reduce tensile forces of bottom slabs which could cause fatal damage of concrete floating structures. We performed a parametric study on the dimensions of this new system and investigate the sensitivity of the parameters to the behavior. In order to investigate various cases efficiently, we developed a simple two-step static analysis method for the fluid-structure interaction. An optimum system is derived from the investigation of the analysis results, weights and drafts of the hybrid structure. This study shows that introducing this new system to concrete floating structures is an effective way to reduce the tensile force of the bottm slab of such a floating structure. Also, it was found that when the length of the semi-submersible module is about 15%, the behavior would be optimal in the considered case.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.2
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• pp.64-74
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• 1997

The necessity and importance of fatigue failure to variable load has been appreciated as the structural design technique develops and use of high tensile steel is increasing. This is much more appreciated for a large ship such as VLCC. The rigorous fatigue analysis and safety assessment should be, hence, carried out at the design stage to avoid the possibility of fatigue failure and to achieve the design result having a sufficient structural safety to fatigue strength. This paper deals with an efficient spectral fatigue analysis of ship structures by introducing the concept of stress influence coefficient. In the process included are probabilistic loading analysis, evaluation of long-term distribution of stress range and estimation of fatigue life applying the spectral fatigue analysis. An integrated computer program has been developed in which reliability analysis to fatigue strength is also included and has been applied to D/H VLCC.

• Journal of the Society of Naval Architects of Korea
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• v.40 no.5
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• pp.53-59
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• 2003

Ocean space utilization using VLFS(Very Large Floating Structures) can provide environmental impact free space by allowing sea water flow freely through the floating structure. Use of Pontoon type VLFS for that purpose needs employment of breakwaters for reduction of wave effects. Therefore, in order to maximize advantage of environmental impact free structure, the breakwater should be the one that can allow water flow freely through it, too. In this paper hydroelastic response of a pontoon type structure is analyzed considering breakwaters which allow water flow through its opening at bottom of the breakwaters. Mode superposition technique is used for solving equation of flexible body while interactions between the pontoon and breakwaters is considered based on generalized mode concept. Bi-quadratic nine node higher-order boundary element method is adopted for more accurate numerical treatment near sharp edged body shape. Performance of various combinations of breakwaters is investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.105-112
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• 2005

Recently, Various structural systems for skyscrapers are studied as structures are more higher. The mega frame system of all, which is the structural system developed recently, are considered as a suitable structural system for skyscrapers. This structural system has sufficient stiffness for the lateral forces with mega-columns which consist of many columns and mega-girders which consist of girders with large stiffness or trusses. But there is no efficient analysis method and a design method for it. Therefore, an efficient analytical model, which has only DOFs selected by the user using the matrix condensation technique, is proposed in this study to obtain accurate results in significantly reduced computational time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.1-9
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• 2003

In GRID environments, an efficient load balancing algorithm should be adopted since the system performances of GRID system are not homogeneous. In this work, a new two-step mesh-partitioning scheme based on the graph-partitioning scheme was introduced to consider the difference of system performance. In the two-step mesh-partitioning scheme, the system performance weights were calculated to reflect the effect of heterogeneous system performances and WEVM(Weighted Edge and vertex Method) was adopted to minimize the increase' of communications. Numerical experiments were carried out in multi-cluster environment and WAN (Wide Area Network) environment to investigate the effectiveness of the two-step mesh-partitioning scheme.

• Journal of Ocean Engineering and Technology
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• v.14 no.2
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• pp.19-27
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• 2000

In this paper hydroelastic responses of a very large floating structure(VLFS) are studied theoretically. We have been developed the source and dipole distribution method and pressure distribution method to evaluate the hydrodynamic pressures. The problem of vertical structural responses due to waves are calculated by using finite element method(FEM) and modal expansion method of a free-free beam Hydroelastic responses of VLFS in waves are computed by four methods developed in this paper. As a result the theoretical results of motion responses show good agreements with experimental ones.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.5
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• pp.34-40
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• 2004

Very Large Floating Structure(VLFS) is regarded as one of promising candidates for the future utilization of ocean space. VLFS has the merits of small environmental effect. short construction term, easiness for extension and removal. It is well known that hydroelastic response is one of major design concerns of such a huge structure. Most of studies on the hydroelastic analysis of VLFS assumed uniform mass and bending stiffness. In case of a floating hotel where noticeable change of mass and stiffness at the hotel part is expected. it is necessary to investigate the effect of nonuniform mass and bending stiffness on the hydroelastic response. A model test of a pontoon type VLFS with nonuniform bending stiffness carried out for performance evaluation of a floating marina-hotel-convention center is described in this paper. Through investigation of model test results and comparison with numerical analysis using eigenfunction method, effect of the variation of bending stiffness is discussed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.82-89
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• 2016

In this study, we proposed a pier of pontoon-type, "Very Large Floating Structure" (VLFS), with the length of 500m, breadth of 200 m and height of 2 m in Yeosu domestic port. Since this structure ought to endure wave loads for long periods at sea, it is essential to analyze the wave response characteristics. Direct-method is used to analyze the fluid-structure problem and the coupled motion of equation is used to obtain response results. The structural part is calculated by using finite element method (FEM) and the fluid part is analyzed by using boundary element method (BEM). Dynamic responses caused by the elastic deformation and rigid motion of structure are analyzed by numerical calculation. To investigate response characteristics of the pier in regular waves, several factors such as the wavelength, water depth, wave direction and flexural rigidity of structure are considered. As a result, wave response of pier changed at the point of $L/{\lambda}$ 1.5 and represented the torsional phenomenon according to the various incident waves. And the responses showed increasing tendency as the water depths increase at the incident point in case of $L/{\lambda}=8.0$ and peak point of vertical displacement amplitude moved from side to side as the flexural rigidity of structure changes.