• 물과 미래
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• 제22권2호
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• pp.160-167
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• 1989

• 한국수소및신에너지학회논문집
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• 제31권1호
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• pp.160-168
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• 2020

Depending on the water depth and composition of seabed, there exist different alternatives for the wind turbine supporting structures. Among several types of the structures, the monopile foundation is the dominant solution for support structure, accounting for over 80% of the offshore wind turbines in Europe. To develop the monopile foundation suitable for domestic ocean environment, a basic design of a transition piece was carried out. This paper presents the design procedure of a flange connected transition piece and results of the structural safety assessment.

• Wind and Structures
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• 제21권6호
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• pp.609-623
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• 2015

Seismic reliability analysis of a jacket-type support structure for an offshore wind turbine was performed. When defining the limit state function by using the dynamic response of the support structure, a number of dynamic calculations must be performed in a First-Order Reliability Method (FORM). That means analysis costs become too high. In this paper, a new reliability analysis approach using a static response is used. The dynamic effect of the response is considered by introducing a new parameter called the Peak Response Factor (PRF). The probability distribution of PRF can be estimated by using the peak value in the dynamic response. The probability distribution of the PRF was obtained by analyzing dynamic responses during a set of ground motions. A numerical example is presented to compare the proposed approach with the conventional static response-based approach.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.110-118
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• 2008

This thesis introduces a study conducted by ANSYS, Finite Element Analysis program, on dynamic behavior by thickness of a chord and a brace of a jacket typed marine structure. As load condition to work on offshore structures is getting much more various, it becomes more important to design the structures and operate them. In addition, stability is also required. As the result of this study, it was proved that wind and wave load gives more affection on frequency than on added mass in the Modal Analysis. Also, the chord and brace affect stiffness more than diagonal brace according to sensitivity analysis.

• 한국해양공학회지
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• 제10권2호
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• pp.13-19
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• 1996

For fatigue analsis of offshore structures, existing methods have been reviewed and a computer code has been developed on PC. As methods to estimate the probabillity distribution of the fatigue stress, three methods(the deterministic method, the stochastic method, and the simplified method) are used in this code, to choose the appropriate method according to the situations. This code estimates damage ratios, fatigue lives, and probabilities of fatigue failure considering scatterness of SN-data, based on linear damage rule and SN-curves. Also, allowable stress for the design extreme wave can calculated by the simplified method.

• Wind and Structures
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• 제32권4호
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• pp.341-354
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• 2021

Articulated towers are one of the class of compliant offshore structures that freely oscillates with wind and waves, as they are designed to have low natural frequency than ocean waves. The present study deals with the dynamic response of a double-pendulum articulated tower under hydrodynamic and aerodynamic loads. The wind field is simulated by two approaches, namely, single-point and multiple-point. Nonlinearities such as instantaneous tower orientation, variable added mass, fluctuating buoyancy, and geometrical nonlinearities are duly considered in the analysis. Hamilton's principle is used to derive the nonlinear equations of motion (EOM). The EOM is solved in the time domain by using the Wilson-θ method. The maximum, minimum, mean, and standard deviation and salient power spectral density functions (PSDF) of deck displacement, bending moment, and central hinge shear are drawn for high and moderate sea states. The outcome of the analyses shows that tower response under multiple-point wind-field simulation results in lower responses when compared to that of single-point simulation.

• Steel and Composite Structures
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• 제22권5호
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• pp.1085-1114
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• 2016

This paper investigates the transverse impact response for ultra lightweight cement composite (ULCC) filled pipe-in-pipe structures through a parametric study using both a validated finite element procedure and a validated theoretical model. The parametric study explores the effect of the impact loading conditions (including the impact velocity and the indenter shape), the geometric properties (including the pipe length and the dimensions of the three material layers) as well as the material properties (including the material properties of the steel pipes and the filler materials) on the impact response of the pipe-in-pipe composite structures. The global impact responses predicted by the FE procedure and by the theoretical model agree with each other closely. The parametric study using the theoretical approach indicates the close relationships among the global impact responses (including the maximum impact force and the maximum global displacement) in specimens with the equivalent thicknesses, proposed in the theoretical model, for the pipe-in-pipe composite structures. In the pipe-in-pipe composite structure, the inner steel pipe, together with the outer steel pipe, imposes a strong confinement on the infilled cement composite and enhances significantly the composite action, leading to improved impact resistance, small global and local deformations.

• 한국생산제조학회지
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• 제19권6호
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• pp.883-888
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• 2010

This study have goal with conceptual design for Offshore Structures of high pressure control valve for localization. Ball valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25 In order to localize the Offshore Structures high pressure control valve. Numerical simulation using CFD (Computational Fluid Dynamic) in order to predict a mass flow rate and a flow coefficient form flow dynamic point of view. The working fluid assumed the glycerin (C3H8O3). The valve inlet and outlet setup a pressure boundary condition. The outlet pressure was fixed by atmospheric pressure and calculated until increasing 1bar to 10bar. CFD analysis used STAR-CCM+ which is commercial code and Governing equations were calculated by moving mesh which is rotated 90 degrees when ball valve operated opening and closing in 1 degree interval. The result shows change of mass flow rate according to opening and closing angle of valve, Flow decrease observed open valve that equal percentage flow paten which is general inclination of ball valve. Relation with flow and flow coefficient can not be proportional according to inlet pressure when compare with mass flow rate. Because flow coefficient have influence in flow and pressure difference. Namely, flow can be change even if it has same Cv value. The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and seat structure.

• 대한토목학회논문집
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• 제31권6A호
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• pp.399-408
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• 2011

최근 스마트 센서를 활용한 구조물의 건전성 모니터링 및 손상 탐색 기법에 대한 연구가 활발히 진행되고 있다. 그 중에서도 광섬유 센서 중 하나인 FBG(fiber Bragg grating) 센서는 경량이고, 내구성이 좋으며, 전자기적 영향이 없을 뿐 아니라 한 가닥으로 여러 지점에서의 계측이 가능한 장점을 가지고 있어 많은 연구와 적용이 시도되고 있다. 이 논문에서는 이러한 FBG 센서를 활용하여 재킷식 해양구조물에 발생하는 손상을 탐색하는 연구를 수행하였으며, 특히 구조물에서 계측된 자료로부터 여러 환경요인을 제거하고 보다 손상에 민감한 특성을 보기 위하여 주성분 분석 기법 적용에 관한 연구를 중점적으로 수행하였다. 제안한 방법의 검증을 위하여 시험조류발전소 구조물의 축소 모델을 활용하여 하중 및 온도 등의 외부 환경이 다른 조건에서 실내 실험을 수행하였고, 이로부터 본 논문에서 제안한 방법이 외부 환경의 영향을 최소화하여 보다 손상을 민감하게 탐색함을 확인하였다.

• 한국해양공학회지
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• 제26권6호
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• pp.7-13
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• 2012

This paper presents a numerical study of the wave loads acting on offshore structures using a Cartesian-grid-based flow simulation method. Finite volume discretization with a volume-of-fluid (VOF) method is adopted to solve two-phase Navier-Stokes equations. Among the many variations of the VOF method, the CICSAM scheme is applied. The body boundary conditions are satisfied using a porosity function, and wave generation is carried out by using transient (wave or damping) zone approaches. In order to validate the present numerical method, three different basic offshore structures, including a sphere, Pinkster barge, and Wigley model, are numerically investigated. First, diffraction and radiation problems are solved using the present numerical method. The wave exciting and drift forces from the diffraction problems are compared with potential-based solutions. The added mass and wave damping forces from the radiation problems are also compared with the potential results. Next, the wave-induced motion responses of the structures are calculated and compared with the existing experimental data. The comparison results are fairly good, showing the validity of the present numerical method.