• Title/Summary/Keyword: offshore structures

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Basic Design of a Flange Connected Transition Piece between Offshore Wind Turbine and Monopile Foundation (해상풍력 터빈과 모노파일 하부기초를 연결하는 플랜지 방식 트랜지션 피스의 기본설계)

  • LEE, KANGHEE;PARK, SUNGGYU;KIM, GEONHO;HWANG, TAEGYU
    • Transactions of the Korean hydrogen and new energy society
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    • v.31 no.1
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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.

Dynamic reliability analysis of offshore wind turbine support structure under earthquake

  • Kim, Dong-Hyawn;Lee, Gee-Nam;Lee, Yongjei;Lee, Il-Keun
    • Wind and Structures
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    • v.21 no.6
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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.

A Study on the Sensitivity of Dynamic Behavior of Jacket Type Offshore Structure (자켓형 해양 구조물의 동적거동에 대한 민감도 연구)

  • Lee, Jung-Tak;Lee, Kang-Su;Shin, Sang-Hak;Son, Choong-Yul
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2008.04a
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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.

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A Review on Fatigue Analysis of Offshore Structures and Development of a Computer Program (해양구조물의 피로해석기법에 대한 검토 및 전산프로그램의 개발)

  • 이현엽
    • Journal of Ocean Engineering and Technology
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    • v.10 no.2
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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.

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Aerodynamic and hydrodynamic force simulation for the dynamics of double-pendulum articulated offshore tower

  • Zaheer, Mohd Moonis;Islam, Nazrul
    • Wind and Structures
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    • v.32 no.4
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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.

A numerical and theoretical investigation on composite pipe-in-pipe structure under impact

  • Wang, Yu;Qian, Xudong;Liew, J.Y. Richard;Zhang, Min-Hong
    • Steel and Composite Structures
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    • v.22 no.5
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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.

A Fundamental Study on Offshore Structures of high pressure control valve (해양구조물용 고압 컨트롤 밸브에 대한 기초 연구)

  • Lee, Chi-Woo;Jang, Sung-Cheol
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.6
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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.

Development of a Damage Monitoring Technique for Jacket-type Offshore Structures using Fiber Bragg Grating Sensors (광섬유 브래그 격자 센서를 활용한 재킷식 해양구조물의 손상 감지 기법 개발)

  • Park, Hyun-Jun;Koo, Ki-Young;Yi, Jin-Hak;Yun, Chung-Bang
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.6A
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    • pp.399-408
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    • 2011
  • Development of smart sensors for structural health monitoring and damage detection has been advanced remarkably in recent years. Nowadays fiber optic sensors, especially fiber Bragg grating (FBG) sensors, have attracted many researchers' interests for their attractive features, such as multiplexing capability, durability, lightweight, electromagnetic interference immunity. In this paper, a damage detection approach of jacket-type offshore structures by principal component analysis (PCA) technique using FBG sensors are presented. An experimental study for a tidal current power plant structure as one of the jacket-type offshore structures was conducted to investigate the feasibility of the proposed method for damage monitoring. It has been found that the PCA technique can efficiently eliminate environmental effects from measured data by FBG sensors, resulting more damage-sensitive features under various environmental variations.

Numerical Study on Wave-induced Motion of Offshore Structures Using Cartesian-grid based Flow Simulation Method (직교 격자계 기반 유동해석기법을 이용한 파랑 중 해양구조물의 운동 해석)

  • Nam, Bo Woo;Kim, Yonghwan;Yang, Kyung Kyu;Hong, Sa Young;Sung, Hong Gun
    • Journal of Ocean Engineering and Technology
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    • v.26 no.6
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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.