• Title, Summary, Keyword: Offshore Structures

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History of Offshore Engineering Development

  • Choi, Han-Suk
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.249-252
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    • 2006
  • This paper introduces a review and literature study of offshore engineering and constructions from 1920s to 2000s. The study was focused on the literature survey and the history of Brown & Root and J. Ray McDermott in the Gulf of Mexico and other offshore areas Understanding the offshore history and background of offshore development is an essential ingredient for the initial conceptual design. This study was motivated to enhance the capacity of conceptual design and Front End Engineering Design (FEED) of offshore structures in Korea.

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Active Control of Offshore Structures for Wave Response Reduction Using Probabilistic Neural Network

  • Kim, Doo-Kie;Kim, Dong-Hyawn;Chang, Sang-Kil;Chang, Seong-Kyu
    • Journal of Ocean Engineering and Technology
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    • v.20 no.5
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    • pp.1-8
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    • 2006
  • Offshore structures are subjected to wave, wind, and earthquake loads. The failure of offshore structures can cause sea pollution, as well as losses of property and lives. Therefore, safety of the structure is an important issue. The reduction of the dynamic response of offshore towers, subjected wind generated random ocean waves, is a critical problem with respect to serviceability, fatigue life and safety of the structure. In this paper, a structural control method is proposed to control the vibration of offshore structures by the probabilistic neural network (PNN). The state vectors of the structure and control forces are used for training patterns of the PNN, in which control forces are prepared by linear quadratic regulator (LQR) control algorithm. The proposed algorithm is applied to a fixed offshore structure under random ocean waves. Active control of the fixed offshore structure using the PNN control algorithm shows good results.

Safety Estimation of High Pressure Drop Control Valve for Offshore Structures (해양플랜트용 고압.고차압 제어밸브의 구조 안전성 평가)

  • Kim, Jae-Woong
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.20 no.5
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    • pp.553-558
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    • 2011
  • This study have goal with conceptual design for offshore structures of high pressure drop control valve for localization 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 drop control valve. This study is numerical analysis for zambil offshore project of high pressure drop control valve. The solver which ANSYS workbench used for offshore structures analysis. The working fluids assumed the glycerin(C3H8O3). 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 disk structure. In this study a multi-disk of high pressure drop control valve is designed and manufactured. Then, the flow rate and high pressure dorp of fluids flowing in the high pressure drop control valve is CAE. So, this system can be easily substituted for the existing zambil offshore project system. Finally, safety estimation for trim design of high pressure drop control valve for offshore structures.

A Study on the Application of Skirt Plates on Jacket Support Structures of Offshore Wind Turbines

  • Choi, Byeong-Ryoel;Choi, Han-Sik;Jo, Hyo-Jae;Lee, Sang-Hyep;Park, Young-Ho
    • Journal of Advanced Research in Ocean Engineering
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    • v.4 no.2
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    • pp.47-52
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    • 2018
  • The Korea Offshore Wind Power (KOWP) is planning to construct offshore wind energy farms with an overall rated power of 2.5 GW in the south-western coast of the country until 2019. Various types of support structures for offshore wind turbines have been proposed in the past. Nevertheless, in South Korea, jacket structures have in general, been applied as support structures for offshore wind turbines owing to the many accumulated experiences and know-how regarding this kind of support structure. The choice of offshore structure is mainly influenced by site conditions such as seabed soil type and sea environment during installation. In installing jacket sets on the seabed, the mudmat is necessary to maintain the equilibrium of the jacket without the aid of additional devices. Hence, this study proposes the installation of skirt plates underneath the bottom frame of jackets in order to improve the installation stability of jacket structures under rougher sea conditions. To confirm the effect of skirt plates, installation stability analyses considering overturning, sliding and bearing capacity have been performed. From the results, it is shown that jacket structures with skirt plates can contribute to improving the sliding stability of the structures of new wind power farms, while providing economic benefits.

Quasi real-time and continuous non-stationary strain estimation in bottom-fixed offshore structures by multimetric data fusion

  • Palanisamy, Rajendra P.;Jung, Byung-Jin;Sim, Sung-Han;Yi, Jin-Hak
    • Smart Structures and Systems
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    • v.23 no.1
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    • pp.61-69
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    • 2019
  • Offshore structures are generally exposed to harsh environments such as strong tidal currents and wind loadings. Monitoring the structural soundness and integrity of offshore structures is crucial to prevent catastrophic collapses and to prolong their lifetime; however, it is intrinsically challenging because of the difficulties in accessing the critical structural members that are located under water for installing and repairing sensors and data acquisition systems. Virtual sensing technologies have the potential to alleviate such difficulties by estimating the unmeasured structural responses at the desired locations using other measured responses. Despite the usefulness of virtual sensing, its performance and applicability to the structural health monitoring of offshore structures have not been fully studied to date. This study investigates the use of virtual sensing of offshore structures. A Kalman filter based virtual sensing algorithm is developed to estimate responses at the location of interest. Further, this algorithm performs a multi-sensor data fusion to improve the estimation accuracy under non-stationary tidal loading. Numerical analysis and laboratory experiments are conducted to verify the performance of the virtual sensing strategy using a bottom-fixed offshore structural model. Numerical and experimental results show that the unmeasured responses can be reasonably recovered from the measured responses.

Analysis and performance of offshore platforms in hurricanes

  • Kareem, Ahsan;Kijewski, Tracy;Smith, Charles E.
    • Wind and Structures
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    • v.2 no.1
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    • pp.1-23
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    • 1999
  • Wind effects are critical considerations in the design of topside structures, overall structural systems, or both, depending on the water depth and type of offshore platform. The reliable design of these facilities for oil fields in regions of hostile environment can only be assured through better understanding of the environmental load effects and enhanced response prediction capabilities. This paper summarizes the analysis and performance of offshore platforms under extreme wind loads, including the quantification of wind load effects with focus on wind field characteristics, steady and unsteady loads, gust loading factors, application of wind tunnel tests, and the provisions of the American Petroleum Institute Recommended Practice 2A - Working Stress Design (API RP 2A-WSD) for the construction of offshore structures under the action of wind. A survey of the performance of platforms and satellite structures is provided, and failure mechanisms concerning different damage scenarios during Hurricane Andrew are examined. Guidelines and provisions for improving analysis and design of structures are addressed.

Methods for Nonlinear Structural Response Analysis of Offshore Structures with Passive Fire Protection under Fires (해양플랜트 구조물의 화재 사고 시 PFP 효과를 고려한 비선형 구조응답 해석 기법에 대한 연구)

  • Kim, Jeong Hwan;Lee, Dong Hun;Ha, Yeon Chul;Kim, Bong Ju;Seo, Jung Kwan;Paik, Jeom Kee
    • Journal of Ocean Engineering and Technology
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    • v.28 no.4
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    • pp.294-305
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    • 2014
  • In offshore structures, fire is one of the most important hazardous events. The concern of fires has recently been reflected in the rules and quantified risk assessment based design practice. Within the framework of quantified risk assessment and the management of offshore installations, therefore, more refined computations of the consequences or hazardous action effects due to fire are required. To mitigate fire risk, passive fire protection(PFP) is widely used on offshore structures. This study presents methods for a nonlinear structural response analysis considering the PFP effects under fires. It is found that a structural response analysis is most likely to use valuable technology for the optimization and design of offshore structures with PFP. Thermal and structural response analyses have been performed using LS-DYNA and FAHTS/USFOS. The results of these structural response analyses are compared with each other.

Review of Offshore Industry and Engineering Development

  • Lee, Seung-Keon;Choi, Han-Suk
    • Journal of Ocean Engineering and Technology
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    • v.20 no.4
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    • pp.1-8
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    • 2006
  • This paper introduces a review and literature study of offshore engineering and constructions from 1920s to 2000s. The study was focused on the literature survey and the history of Brawn & Root and J. Ray McDermott in the Gulf of Mexico and other offshore areas. The fluctuations of oil and gas prices have been strongly influenced the development of offshore industry since its very beginning. Scientific projects on the space and under the earth had played very important roles in offshore development in 1950s and 1960s. Deepwater developmentshave been influenced by the computer assisted analysis and design in 1970s and 1980s. Innovative technology provided continuous developments of deepwater structures in 1990 and after.

A Study on the vibration characteristics of offshore wind turbine tower including seabed soil-structure interaction (해저지반-구조물 상호작용을 고려한 해상풍력발전타워의 진동특성)

  • Lee, Jung-Tak;Lee, Kang-Su;Son, Choong-Yul;Park, Jong-Vin
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.416-422
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    • 2009
  • Offshore wind turbine are subjected to more various loads than general land structures and the stability of structures is supported by the piles driven deeply in the subsoil. So it is more important for offshore structures to consider seabed soil-structure interaction than land structures. And the response of a fixed offshore structure supported by pile foundations is affected by resist dynamics lateral loading due to wave forces and ocean environmental loads. In this study, offshore wind tower response are calculated in the time domain using a finite element package(ANSYS 11.0). Several parameters affecting the vibration characteristics of the natural frequency and mode shape and the tower response have been investigated.

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Experimental Study on the On-line Monitoring of Offshore Structures Using Acoustic Emission Technology (음향방출법을 이용한 해양구조물의 온라인 감시에 관한 실험적 연구)

  • Won, Soon-Ho;Cho, Kyung-Shik
    • Journal of Ocean Engineering and Technology
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    • v.13 no.3B
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    • pp.73-82
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    • 1999
  • In this research, an experimental study is presented to check the possibilities of offshore structures monitoring using AE techniques. The underwater transducer and preamplifier are fabricated. And, it is proved that this unit can be used for the detection of AE in offshore structures. Wave propagation studies have shown that supplementary attenuations due to seawater are significantly reducing the detection range of the sensors. It excludes the possibility of offshore structures monitoring with a small number of sensors. We conclude that AE waves would be correctly detected for a path of about 3m. Tubular joints have been tested in air and underwater using simulated elastic wave. Ability of AE techniques to detect and locate cracks early in their evolution has been demonstrated. Several parameters of AE generation have been set in evidence. It has also been shown that crack development goes with an increase of AE parameter. Conclusively, it is shown that AE techniques can provide practical alternatives to present methods being used for inspection of deep-water offshore structures undergoing structural degradation due to fatigue crack growth.

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