• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.1
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• pp.36-41
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• 2014

A floating offshore structure has high tendency to occur the buckling when compressive, bending and shear loads applied. When the buckling is occurred, in-plane stiffness of structure is remarkably decreased. And it has a harmful effect on the local structural strength as well as global structural strength. In the present study, it has been investigated the ultimate strength of tubular members which is located between a floater and a damping plate of the floating pendulum wave energy converter. Nonlinear finite element method is conducted using the initial imperfection according to 1st buckling mode which is obtained from the elastic buckling analysis. It is also noted the ultimate bending strength characteristic varying with a diameter, thickness and stiffeners of the tubular member.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.19-25
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• 2001

Structural design requirements for very large floating structures(VLFS) are different corresponding to this purpose and structural type. In this study, the structural design procedure of VLFS is described, composing of the following processes : construction of design conditions. choice of structural types and main materials, estimation of structural design loads, determination of structural arrangements, and scantling of structural members. As an example of practical application, the initial structural design of floating airport and container terminal for Pusan is demonstrated.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.2
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• pp.26-32
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• 2001

In this paper, elastic responses of a floating structure in waves with a breakwater are presented. The method of source-dipole distribution is used to analyze the velocity potentials for the fluid region. The deflections of structure are expanded approximately in terms of natural mode functions of free-free beam. The model for present calculation is a floating plate with an length of 1000m and the hydroelastic responses for a floating structure with a straight breakwater are shown. The effects of distance between breakwater and structure, bending rigidity and relative length of regular waves are examined.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.55-55
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• 2011

연안 및 해안공학의 발달과 더불어 부유식방파제의 기능적 효율성이 중요시 되고 있다. 흔히 사용되어오던 착저식방파제는 설치에 많은 시간과 경비가 소요되고 환경 및 생태계에 많은 변화를 줄 수 있으며, 설치 예정지의 수리학적 특성 등의 여건에 많은 제약을 받는 단점이 있다. 부유식방파제는 일본 등의 선진국을 중심으로 활용이 잦아지고 있는 방파제로서 수면 위에 설치되기 때문에 수중 생태계에 미치는 영향이 적은 친환경방파제이다. 또한 기존에 시공된 중력식방파제와는 달리 수심에 제한을 덜 받고, 공사기간이 짧기 때문에 경제적이다. 실제 시공사례로는 2007년 마산 원전항에 완공된 부유식방파제가 대표적이며, 지금까지도 부유식방파제에 대한 여러 연구자들의 관심이 증가하고 있는 추세이다. 방파제뿐만 아니라 우리나라처럼 국토의 면적이 작은 지역에서 증가하는 해상물동량을 소화하기 위해서 부유식방파제 등을 이용한 항만의 시공이 필요한 실정이다. 이러한 부유식방파제의 분석적인 측면에 있어서 수치해석은 파랑과 구조물의 상호작용을 해석하는 데 한계가 있으며, 부유식방파제 단면형상을 정확하게 재현할 수 없으므로, 수리모형실험을 통한 부유식방파제의 연구가 필요할 것으로 판단된다. 최근 기술의 발달로 인한 유동장 해명이 가능해 졌으며, PIV(Particle image velocimetry) 및 LDV시스템은 다양한 분야에서 응용되고 있다. 특히, LDV시스템은 측정하려는 한 지점에 대하여 레이저 빔을 단면(Cross-section)으로 만들고 입자의 산란광을 후방산란(Back scatter)으로 받아서 도플러 효과를 이용, 속도에 대한 주파수를 획득하며, 유속을 측정하는 장비로 매우 높은 정확도와 비접촉식 이라는 장점을 가지고 있다. 또한, PIV 시스템에 비하여 측정시간이 오래 걸리는 반면 데이터를 가공하지 않고 활용할 만큼 높은 정확성을 가지고 있다. 본 연구에서는 수리모형실험을 통하여 단독형, 2열형 및 3열형 부유식방파제의 형상, 흘수 및 거리를 변화시키며 유동장을 수집하였으며, 방파성능에 따른 와의 생성 및 소멸시점에서의 파랑변형과의 관계를 분석하였다. 방파제의 형상과 흘수를 달리하여 수리모형실험을 수행하였으며, 와류의 상관관계를 분석하였다. 또한, 연직 2차원 Navier-Stokes 방정식 모형을 이용하여 수치모형실험을 수행하였으며, 수치모형실험 결과와 수리모형실험 결과를 비교 분석하였다. 후방방파제에서 발생되는 파랑은 입사파의 주기가 길어질수록 상대적으로 커지는 현상을 보였으며, 흘수심이 깊어질수록 전방방파제 입사 면에서 자유 수면이 높게 관측되는 결과를 보였다. 또한, 비교적 장주기파랑에 해당하는 입사파랑의 경우 전달파고비 산정에 있어서 설계기준인 0.5를 대다수 초과하는 반면, 3열형 구조에서는 대부분이 0.5이하로 상당히 높은 방파성능 결과를 나타내었다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.1
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• pp.7-17
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• 2016

The present study experimentally considers dynamic performance of large floating wave-offshore hybrid power generation platform in extreme conditions. In order to evaluate the motion performance of the large floating hybrid power generation platform, 1/50 scaled model was manufactured. A mooring line was also manufactured, and free-decay and static pull-out tests were carried out to check the mooring model. A mooring line table was introduced to satisfy the water depth, and environmental conditions were checked. Motion responses in regular waves were measured and complicated environmental conditions including wave, wind, and current were applied to see the dynamic performance in extreme/survival conditions. Maximum motion and acceleration were judged following the design criteria, and maximum offset and mooring tension were also checked based on the rule. The characteristics of hybrid power generation platform are discussed based on these data.

• Journal of the Korean Society for Marine Environment & Energy
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• v.5 no.3
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• pp.35-44
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• 2002

In this paper, the analytic studies on the wave control performance of moored pontoon-type floating breakwater are presented. A two-dimensional eigenfunction expansion method is adopted to study the motion responses and the transmission coefficients of pontoon-type floating breakwater in beam waves. The stiffness coefficients of mooring line are idealized as linear elastic spring. Comparison of the analytical results with a numerical results (FEM) shows good agreement over a wide range of frequencies. The performance of mooed pontoon-type floating breakwater is tested with various design parameters such as sectional geometry, mooring line characteristics and wave frequencies. It is found that the properly designed floating breakwater can be an effective wave control structure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.72-80
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• 2015

In this study, comparative analysis has been performed with regard to a bending stress and deformation at bottom slab of a concrete floating container terminal by live load distributions. In addition, a structural performance and behavior of the floating structure is considered using a numerical analysis. Through reviewed structural performance of a floating structure by live load distribution, the structure presented tensile behavior by two live load cases (A, B, D-type). Then, the other live load cases (C, E, F, G, H, I, J-type) shows compressive behavior. Especially, immoderately compressive stress was generated on bottom slab at specific load distribution. but, that should be decreased through controling buoyancy pre-flexion. Through reviewed structural behavior, slopes of structure by four live load cases (B, E, F, H-type) were exceeded in design criteria of mega-float. It should be estimated that it get out of the load case at loading container. In all, the present study can be considered as a benchmark of a floating container terminal in the absence of analysis and will be used to guide-line about serviceability of concrete floating container terminal.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2006.09a
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• pp.141-144
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• 2006

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.3
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• pp.135-142
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• 2015

Floating offshore structures should be designed by considering the most extreme environmental loadings which may be encountered in their design life. The most severe loading on a wave-offshore wind hybrid power generation system is wave loads. The principal parameters of wave loads are wave length, wave height and wave direction. The wave loads have different effects on the structural behavior characteristic depending on the combination of wave parameters. Therefore, the process of investigation for critical loads based on the individual wave loading parameter is need. Namely, the equivalent design wave should be derived by finding the wave condition which generates the maximum stress in entire wave conditions. Through a series of analysis, an equivalent regular wave height can be obtained which generates the same amount of the hydrodynamic loads as calculated in the response analysis. The aim of this study is the determination of equivalent design wave regarding to characteristic global hydrodynamic responses for wave-offshore wind hybrid power generation system. It will be utilized in the global structural response analysis subjected to selected design waves and this study also includes an application of global structural analysis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.237-243
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• 2019

Floating platforms made of PE (PolyEthylene) are often located in shallows of seas, rivers or lakes. They are widely used for marine pensions, marine pontoons, marine bridges, etc. These products are characterized by good flexibility, recyclability, chemical resistance and weatherability with corrosion resistance. Existing PE floating platforms have a simple structure in which one pipe is fastened to one bracket, but this has limited application, even if a user modifies the arrangement. Therefore, we developed a structure that allows buoyancy pipes of various sizes to be fastened to one bracket and verified the structural safety of the product using the finite element method. From the results of structural analysis for buoyancy pipes of different diameters, the maximum stress ratio was 0.78 compared with allowable criteria of 1.0, which represented sufficient safety for a model with 500 mm diameter pipes. Based on the results of this study, further research to evaluate the structural safety of various floating platforms can be carried out in the further; it will also be necessary to establish related evaluation criteria.