Artykuły w czasopismach: „Offshore Structure”

1

Kouichirou, Anno, i Takeshi Nishihata. "DEVELOPMENT ON OFFSHORE STRUCTURE". Coastal Engineering Proceedings 1, nr 32 (31.01.2011): 50. http://dx.doi.org/10.9753/icce.v32.structures.50.

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Authors have developed the offshore structure for control of sea environment named S-VHS construction method, which is composed of the sloping top slit-type caisson and steel pipe piles. The sloping top form enables to realize the remarkable reduction of wave force exerted on the dike body compared with the conventional one. In this paper, hydraulic feature with wave dissipation ability and wave force reduction effect are verified through some hydraulic experiments. After the preliminary study for the valid structure form, reflection and transmission ability for the selected structure models were tested with the hydraulic experiment relevant to the ratio of caisson width and wave length. Finally, wave force experiment was executed and it revealed the performance of wave force reduction. Based on the results, we proposed specific design wave force formula for S-VHS construction method.

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2

Soares, C. Guedes. "Offshore structure modelling". Applied Ocean Research 17, nr 6 (grudzień 1995): 391–92. http://dx.doi.org/10.1016/s0141-1187(96)00012-0.

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Hancock, Michael V. "4909672 Offshore structure". Marine Pollution Bulletin 21, nr 7 (lipiec 1990): 362. http://dx.doi.org/10.1016/0025-326x(90)90807-k.

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Frieze, Paul A. "Compliant offshore structure". Marine Structures 6, nr 4 (1993): 381–86. http://dx.doi.org/10.1016/0951-8339(93)90005-n.

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Veletsos, A. S., A. M. Prasad i G. Hahn. "Fluid-structure interaction effects for offshore structures". Earthquake Engineering & Structural Dynamics 16, nr 5 (lipiec 1988): 631–52. http://dx.doi.org/10.1002/eqe.4290160502.

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Ku, Namkug, Sol Ha i Myoung-Il Roh. "Crane Modeling and Simulation in Offshore Structure Building Industry". International Journal of Computer Theory and Engineering 6, nr 3 (2014): 278–84. http://dx.doi.org/10.7763/ijcte.2014.v6.875.

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YOKURA, Takahito. "Ship and Offshore Structure". JOURNAL OF THE JAPAN WELDING SOCIETY 81, nr 5 (2012): 402–6. http://dx.doi.org/10.2207/jjws.81.402.

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Vickers, Dean, L. Mahrt, Jielun Sun i Tim Crawford. "Structure of Offshore Flow". Monthly Weather Review 129, nr 5 (maj 2001): 1251–58. http://dx.doi.org/10.1175/1520-0493(2001)129<1251:soof>2.0.co;2.

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Suzuki, Yoshio, Mitsuok Yamamoto i Hisashi Hosomi. "4692065 Offshore unit structure". Marine Pollution Bulletin 19, nr 1 (styczeń 1988): 43. http://dx.doi.org/10.1016/0025-326x(88)90760-6.

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Jung, Dong-Ho, Hyeon-Ju Kim, Sa-Young Hong i Ho-Saeng Lee. "Offshore structure for OTEC". Journal of the Korea Society For Power System Engineering 17, nr 3 (30.06.2013): 5–11. http://dx.doi.org/10.9726/kspse.2013.17.3.005.

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Kaiser, Mark J., i Brian F. Snyder. "Offshore wind structure weight algorithms". Ships and Offshore Structures 9, nr 6 (6.02.2014): 551–56. http://dx.doi.org/10.1080/17445302.2013.870772.

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12

Ishiguro, Takayoshi. "Fatigue Design of Offshore Structure". CORROSION ENGINEERING 35, nr 1 (1986): 45–51. http://dx.doi.org/10.3323/jcorr1974.35.1_45.

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13

Chen, Wei, Xingyu Du, Bao-Lin Zhang, Zhihui Cai i Zhongqiang Zheng. "Near-Optimal Control for Offshore Structures with Nonlinear Energy Sink Mechanisms". Journal of Marine Science and Engineering 10, nr 6 (14.06.2022): 817. http://dx.doi.org/10.3390/jmse10060817.

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To improve the safety and reliability of offshore structures subject to wave loading, the active vibration control problem is always one of significant issues in the field of ocean engineering. This paper deals with the near–optimal control problem of offshore structures with a nonlinear energy sink (NES) mechanism. By taking the dominant vibration mode of the offshore structure with the NES into account, a nonlinear dynamic model of the steel–jacket structure subject to wave loading is presented first. Then, using the parameter perturbation approach to solve a nonlinear two–point boundary value problem, an NES–based optimal controller with the form of infinite series sum is presented to suppress the vibration of the offshore structure. Third, an iteration algorithm is provided to obtain the near–optimal controller. Simulation results demonstrate that the NES–based near–optimal controller can mitigate the oscillation amplitude of offshore structures significantly. Moreover, the NES–based optimal controller outperforms the one based on active tuned mass damper.

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14

Gomes, Lizbeth K., i Madhuraj Naik. "Detection of damage in offshore jacket structure using artificial neural network". IOP Conference Series: Earth and Environmental Science 1130, nr 1 (1.01.2023): 012027. http://dx.doi.org/10.1088/1755-1315/1130/1/012027.

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Abstract With industrial growth over the years, geologists have begun to search for offshore sources of oil and natural gas. Most offshore oil-production platforms are jacket type. Offshore jacket structures consist of welded steel space frame. Tubular pipes are opted as they reduce hydrodynamic loads making them highly durable structures. However due to natural phenomenon like cyclones, earthquakes, etc. these structures can get adversely damaged. Apart from that the structure also degrades due to corrosion and fatigue due to the severe conditions it is always exposed to. In many cases physical inspection of the structure for checking damages is not possible due to unfavourable onsite conditions or lack of trained professionals. Hence there is a need to develop alternatives solutions. In recent years much research has been done in the application of Artificial Neural Networks (ANN) in Civil Engineering. ANN are computation systems that are inspired by biological neural systems. This paper aims at creating an ANN to identify damage in an offshore jacket structure using the modal parameters. The training set for the ANN is obtained by using a finite element software. The ANN is then tested using a test set and then it will be used to predict the structural damage in an offshore jacket structure.

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15

Hossin, M., i H. Marzouk. "Crack spacing for offshore structures". Canadian Journal of Civil Engineering 35, nr 12 (grudzień 2008): 1446–54. http://dx.doi.org/10.1139/l08-073.

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The main focus of this investigation is directed toward the examination of crack-spacing expressions suitable for offshore concrete structure applications. Offshore structures are unique structures that are constantly exposed to harsh environmental conditions, including exposure to seawater and sea spray. The splash zone of an offshore structure is the section of the platform that is the most exposed to both a harsh marine environment and seawater. The design of offshore structures is controlled by mandatory design codes to ensure structural safety and integrity. Most of the available expressions for crack spacing were developed for building structures using normal-strength concrete and normal concrete cover. However, offshore structures are built using high-strength concrete with a thick concrete cover. Very little information is published on the crack analysis of high-strength concrete with a thick concrete cover for offshore applications. An experimental testing program was designed to examine the effects of concrete cover and the bar spacing of normal- and high-strength concrete on crack spacing. The different code expressions are evaluated with respect to the experimental results.

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Vuong, Nguyen Van, i Mai Hong Quan. "Fatigue analysis of jacket support structure for offshore wind turbines". Journal of Science and Technology in Civil Engineering (STCE) - NUCE 13, nr 1 (31.01.2019): 46–59. http://dx.doi.org/10.31814/stce.nuce2019-13(1)-05.

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In the past few decades and up to now, the fossil energy has exerted tremendous impacts on human environments and gives rise to greenhouse effects while the wind power, especially in offshore region, is an attractive renewable energy resource. For offshore fixed wind turbine, stronger foundation like jacket structure has a good applicability for deeper water depth. Once water depth increases, dynamic responses of offshore wind turbine (OWT) support structures become an important issue. The primary factor will be the total height of support structure increases when wind turbine is installed at offshore locations with deeper water depth, in other words the fatigue life of each components of support structure decrease. The other one will experience more wind forces due to its large blades, apart from wave, current forces, when makes a comparison with offshore oil and gas platforms. Summing up two above reasons, fatigue analysis, in this research, is a crucial aspect for design of offshore wind turbine structures which are subjected to time series wind, wave loads and carried out by aiding of SACS software for model simulation (P-M rules and S-N curves) and Matlab code. Results show that the fatigue life of OWT is decreased accordingly by increasing the wind speed acting on the blades, especially with the simultaneous interaction between wind and wind-induced wave. Hence, this should be considered in wind turbine design. Keywords: offshore wind turbine; Jacket structure; fatigue analysis; P-M rules; S-N curves. Received 01 October 2018, Revised 19 November 2018, Accepted 31 January 2019

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17

Zhaowang, Xia, Xu Xiangxi, Ju Fuyu, Wang Zongyao, Lu Zhiwei i Cao Rui. "Study on vibration characteristics of periodic truss structure of offshore platform". Advances in Mechanical Engineering 12, nr 11 (listopad 2020): 168781402097288. http://dx.doi.org/10.1177/1687814020972886.

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Using the band gap properties of the periodic structure, the truss structure of an offshore platform is designed as a one-dimensional periodic conduit structure, and the band gap characteristics are used to realize the vibration control of the truss structure of the offshore platform. The finite element method is used to simulate the vibration characteristics of the periodic conduit, and the influence of the structural parameters (length and wall thickness) of the periodic conduit on the vibration band gap of the periodic conduit is analysed. The frequency response characteristics of the periodic truss structure of an ocean platform are calculated and compared with those of a traditional truss structure. The results show that the periodic truss exhibits better suppression of vibration transmission than the traditional truss, especially for the vibration in the band gap, which is greatly attenuated. This study shows that the periodic structure has broad application prospects in vibration isolation design of truss structures for offshore platforms. The research provides a new technical approach for vibration control of truss structures on offshore platforms.

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18

Abdel Raheem, Shehata E., i Elsayed M. A. Abdel Aal. "Finite Element Analysis for Structural Performance of Offshore Platforms under Environmental Loads". Key Engineering Materials 569-570 (lipiec 2013): 159–66. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.159.

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Offshore structures for oil and gas exploitation are subjected to various ocean environmental phenomena which can cause highly nonlinear action effects. Offshore structures should be designed for severe environmental loads and strict requirements should set for the optimum performance. The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. The structure is discretized using the finite element method, wave force is determined according to linearized Morison equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the one year return period wave and must be able to survive the 100 year return period storm conditions. The results show that the nonlinear response analysis is quite crucial for safe design and operation of offshore platform. Fixed Jacket type offshore platforms under extreme wave loading conditions may exhibit significant nonlinear behavior. The effect of current with different angles when hitting the offshore structure with the wave and wind forces, is very important for calculate the stress, the response displacement and deformation shapes. As the current increase or decrease the effect of wave force according to the hitting angle of current.

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19

Sarpkaya, T. "Offshore Hydrodynamics". Journal of Offshore Mechanics and Arctic Engineering 115, nr 1 (1.02.1993): 2–5. http://dx.doi.org/10.1115/1.2920085.

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In this paper, we present several applied as well as fundamental research problems related to the future needs of the offshore engineering. The paper starts out with a detailed discussion of the current uncertainties and constraints. Then, specific research issues on environmental input conditions, on the role of computational fluid dynamics, and on damping and dynamic response are presented. It is suggested that an appreciation of the input parameters, acquisition of extensive data to properly characterize the ocean environment, development of new methods and tools to acquire relevant data, extensive use of the computational methods, basic/applied research on the dynamic response and damping of structures, use of new materials, science-and-technology transfer from sister disciplines (e.g., aerospace industry, keeping in mind the complexities brought about by the presence of the air-water interface), and other related research will significantly enhance our ability to design and build a variety of safer and economical offshore structures in deeper waters as well as over marginal fields in the next few decades. This herculean effort will require several decades of complementary experimental, numerical and analytical studies of ocean-structure interaction which will serve to elucidate the basic as well as applied fluid mechanics phenomena relevant to the offshore mechanics.

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20

Zhang, Sheng Qiang, Hui Chi Zhang, Mo Lin Li i Wei Xu. "Analysis and Preventive Measures of Offshore Steel Structure Welding Crack". Advanced Materials Research 945-949 (czerwiec 2014): 1254–57. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.1254.

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In recent years, offshore oil & gas industry developed rapidly. Offshore steel structure is the support structure for offshore drilling and production platform, and its welding quality is particularly important in fabrication. This paper aims at the typical welding crack of offshore steel structure, through investigations and experimental analysis, considering the application characteristics of offshore steel structure and site issues, analysis the root causes of welding crack and give the improvement and prevention measures.

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21

Tomasicchio, Giuseppe Roberto, Elvira Armenio, Felice D'Alessandro, Nuno Fonseca, Spyros A. Mavrakos, Valery Penchev, Holger Schuttrumpf, Spyridon Voutsinas, Jens Kirkegaard i Palle M. Jensen. "DESIGN OF A 3D PHYSICAL AND NUMERICAL EXPERIMENT ON FLOATING OFF-SHORE WIND TURBINES". Coastal Engineering Proceedings 1, nr 33 (14.12.2012): 67. http://dx.doi.org/10.9753/icce.v33.structures.67.

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The knowledge of the behavior of floating offshore wind turbines (W/T) under wave and/or wind action remains one of the most difficult challenges in offshore engineering which is mostly due to the highly non-linear response of the structure. The present study describes the design process of a 3D physical experiment to investigate the behavior of the most promising structure technology of floating W/T: spar buoy (SB) and tension leg platform (TLP) under different meteo conditions. In order to properly design the two W/T models, the following topics have been analyzed: mooring lines, mass distribution, appropriate scaling factor and data relative to the geometrical characteristics, wave basin dimensions and wind and waves conditions. In addition, the Smoothed Particle Hydrodynamics method (SPH) (Monaghan 1994) has been considered to simulate the 3D behavior of a floating offshore W/T. In particular, the SPH, calibrated and verified on the basis of the experimental observations, may represent a reliable tool for preliminary test of changes in the floater geometry.

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Braun, Moritz, Alfons Dörner, Kane F. ter Veer, Tom Willems, Marc Seidel, Hayo Hendrikse, Knut V. Høyland, Claas Fischer i Sören Ehlers. "Development of Combined Load Spectra for Offshore Structures Subjected to Wind, Wave, and Ice Loading". Energies 15, nr 2 (13.01.2022): 559. http://dx.doi.org/10.3390/en15020559.

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Fixed offshore wind turbines continue to be developed for high latitude areas where not only wind and wave loads need to be considered but also moving sea ice. Current rules and regulations for the design of fixed offshore structures in ice-covered waters do not adequately consider the effects of ice loading and its stochastic nature on the fatigue life of the structure. Ice crushing on such structures results in ice-induced vibrations, which can be represented by loading the structure using a variable-amplitude loading (VAL) sequence. Typical offshore load spectra are developed for wave and wind loading. Thus, a combined VAL spectrum is developed for wind, wave, and ice action. To this goal, numerical models are used to simulate the dynamic ice-, wind-, and wave-structure interaction. The stress time-history at an exemplarily selected critical point in an offshore wind energy monopile support structure is extracted from the model and translated into a VAL sequence, which can then be used as a loading sequence for the fatigue assessment or fatigue testing of welded joints of offshore wind turbine support structures. This study presents the approach to determine combined load spectra and standardized time series for wind, wave, and ice action.

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Li, Junlai, Weiguo Wu, Yu Wei, Yu Shu, Zhiqiang Lu, Wenbin Lai, Panpan Jia, Cheng Zhao i Yonghe Xie. "Study on Dynamic Response of Offshore Wind Turbine Structure Under Typhoon". Polish Maritime Research 29, nr 1 (1.03.2022): 34–42. http://dx.doi.org/10.2478/pomr-2022-0004.

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Abstract Floating offshore wind turbines are easily affected by typhoons in the deep sea, which may cause serious damage to their structure. Therefore, it is necessary to study further the dynamic response of wind turbine structures under typhoons. This paper took the 5MW floating offshore wind turbine developed by the National Renewable Energy Laboratory (NREL) as the research object. Based on the motion theory of platforms in waves, a physical model with a scale ratio of 1:120 was established, and a hydraulic cradle was used to simulate the effect of waves on the turbines. The dynamic response characteristics of offshore wind turbines under typhoons are systematically studied. The research results clarified that the turbine structure is mainly affected by wave loads under typhoons, and its motion response reaches its maximum value under the action of extreme wave loads. The research results of this paper can provide reference value for the design of offshore wind turbine structures under typhoons.

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Li, Junlai, Weiguo Wu, Yu Wei, Yu Shu, Zhiqiang Lu, Wenbin Lai, Panpan Jia, Cheng Zhao i Yonghe Xie. "Study on Dynamic Response of Offshore Wind Turbine Structure Under Typhoon". Polish Maritime Research 29, nr 1 (1.03.2022): 34–42. http://dx.doi.org/10.2478/pomr-2022-0004.

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Abstract Floating offshore wind turbines are easily affected by typhoons in the deep sea, which may cause serious damage to their structure. Therefore, it is necessary to study further the dynamic response of wind turbine structures under typhoons. This paper took the 5MW floating offshore wind turbine developed by the National Renewable Energy Laboratory (NREL) as the research object. Based on the motion theory of platforms in waves, a physical model with a scale ratio of 1:120 was established, and a hydraulic cradle was used to simulate the effect of waves on the turbines. The dynamic response characteristics of offshore wind turbines under typhoons are systematically studied. The research results clarified that the turbine structure is mainly affected by wave loads under typhoons, and its motion response reaches its maximum value under the action of extreme wave loads. The research results of this paper can provide reference value for the design of offshore wind turbine structures under typhoons.

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Hu, Zheng Zheng, Tri Mai, Deborah Greaves i Alison Raby. "Investigations of offshore breaking wave impacts on a large offshore structure". Journal of Fluids and Structures 75 (listopad 2017): 99–116. http://dx.doi.org/10.1016/j.jfluidstructs.2017.08.005.

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26

Been, K., J. I. Clark i W. R. Livingstone. "Verification and calibration studies for the new CAN/CSA-S472 foundations of offshore structures". Canadian Geotechnical Journal 30, nr 3 (1.06.1993): 515–25. http://dx.doi.org/10.1139/t93-044.

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In June 1992, the Canadian Standards Association (CSA) published a code for the design, construction, and installation of fixed offshore structures. This code is relatively advanced in its application of limit states design to offshore structures. The part dealing with foundations is written as a performance standard. It does not specify resistance factors (or safety factors) to achieve the target reliability of the structure. Although limit states design is common practice among geotechnical engineers, the application of resistance factors is a problem. This paper describes some of the studies and conclusions reached by the Technical Committee in the development of the CSA foundations standard. As a first step, resistance factors were developed by calibration to conventional total factors of safety for the failure mechanisms considered. This approach has severe limitations. In particular, the applicability of safety factors developed for onshore practice or other offshore areas to the ice-dominated environment of Canadian offshore regions is questionable. In addition, many offshore structure designs include consideration of dynamic loading and scour or erosion problems that cannot be satisfactorily dealt with using factors of safety. An example of the problem of applying separate load and resistance factors for a bearing-capacity problem is given to show that load and resistance are not independent of each other. Because of the problems with development of resistance factors, the CSA foundations standard dictates that offshore structure designs include a risk analysis of the foundation system. A simple form of such an analysis for a caisson-retained sand structure is included in the paper. Key words : offshore structures, foundations, standard, safety, limit states design.

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Pfoertner, Saskia, Hocine Oumeraci, Matthias Kudella i Andreas Kortenhaus. "WAVE LOADS AND STABILITY OF NEW FOUNDATION STRUCTURE FOR OFFSHORE WIND TURBINES MADE OF OCEAN BRICK SYSTEM (OBS)". Coastal Engineering Proceedings 1, nr 32 (30.01.2011): 66. http://dx.doi.org/10.9753/icce.v32.structures.66.

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The Ocean Brick System (OBS) is a modular system consisting of hollow concrete precast blocs (10m x 10m x 10m) piled up like cubes and interconnected to create a stiff, light and strong structure which can be used for artificial islands, artificial reefs, elevation of vulnerable low lands, deep water ports, breakwaters and foundation of offshore wind turbines. The paper focuses on the experimental results on the wave loading and the stability of the OBS used as a foundation of the support structure of offshore wind turbines. Diagrams for the prediction of total horizontal forces, vertical forces and overturning moments induced by irregular waves on the OB-structure are derived and verified through additional stability tests and stability analysis.

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Plodpradit, Pasin, Van Dinh i Ki-Du Kim. "Coupled Analysis of Offshore Wind Turbine Jacket Structures with Pile-Soil-Structure Interaction Using FAST v8 and X-SEA". Applied Sciences 9, nr 8 (19.04.2019): 1633. http://dx.doi.org/10.3390/app9081633.

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The coupled analysis between a turbine in operating condition and a complex jacket support structure was formulated in this paper for the reliable evaluation of offshore wind turbine structures including pile-soil-structure interactions (PSSIs). Discussions on the theoretical and simulation aspects of the coupled analysis are presented. The dynamic coupled analysis was implemented in X-SEA program and validated with FAST v8 (fatigue, aerodynamics, structures and turbulence) developed by NREL, USA. By replacing the sub-structural module in the FAST with the component of offshore substructure in the X-SEA, the reaction forces and the turbine loads were calculated in each time step and the results from X-SEA were compared with that from FAST. It showed very good agreement with each other. A case study of a NREL 5MW offshore wind turbine on a jacket support structure was performed. Coupled dynamic analyses of offshore wind turbine and support structures with PSSI were carried out. The results showed that in the coupled analysis, the responses of the structure are significantly less than in the uncoupled analysis. The support structure considering PSSI exhibited decreased natural frequencies and more flexible responses compared to the fixed-support structure. The implemented coupled analysis including PSSI was shown to be more accurate and computationally efficient.

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Damilola, Oluwafemi John, Elakpa Ada Augustine i Nwaorgu Obioima Godspower. "Fatigue Evaluation of Offshore Steel Structures Considering Stress Concentration Factor". International Journal of Research and Review 8, nr 10 (21.10.2021): 307–13. http://dx.doi.org/10.52403/ijrr.20211041.

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The installation of offshore structures and facilities in the marine environment, usually for the production and transmission of oil, gas exploration, electricity, and other natural resources is referred to as offshore construction. Since offshore structures are subjected to changing threats to the environment year-round. Fatigue behavior prediction noticed on these structures should be considered during the design stage. Fatigue is one of the failure mechanisms of offshore steel structures, and it must be investigated properly during system design. The fatigue analysis of offshore structures under drag wave force, total wave force, total moment about the sea bed, and other variables are reviewed thoroughly. The structure's dynamic response becomes a critical aspect in the whole design process. The fatigue analysis was carried out using MATLAB software, material properties of the offshore structure, and wave spectrum characteristics in this study. This study shows the JONSWAP spectrum and stress concentration analysis prediction. The offshore support structure that is predicted during the design phase will help to keep the stress concentration factor below the fatigue threshold and anticipate safe life design, according to the results of the fatigue study. The fatigue performances of tripod and jacket steel support structures in intermediate waters depth are compared in this project (20-50 m). The North Atlantic Ocean is used as a reference site, with a sea depth of 45 meters. The tripod and jacket support structures will be designed by using current industry standards. Keywords: [Fatigue evaluation, North Atlantic Ocean and Failure].

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Zhao, Da Hai, i Jing Lin Zhang. "Vibration Control of Offshore Platform Structure with Friction Dampers". Applied Mechanics and Materials 638-640 (wrzesień 2014): 318–21. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.318.

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The performance of friction dampers to mitigate waves and earthquakes in tower-type offshore platform is investigated in this paper. Taking the offshore platform of TOWER-1 as an example, the equation of motion of offshore platform structure under earthquake and wave loads was established. The response reductions of offshore platform structure by different peak earthquakes were analyzed. The results show that the responses of the tower-type offshore platform structure under wave and earthquake could be effectively reduced by friction damper, and the energy dissipation ability of the friction damper differs in the different floors. The friction dampers give good response reductions in different peak earthquakes, and the response reductions of displacement are better than those of acceleration.

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Sun, Min Young, Ki Yeol Lee i Byung Young Moon. "A Study on the Structural Analysis of Jacket Substructure Related to Offshore Wind Power Environment". Advanced Materials Research 1125 (październik 2015): 387–91. http://dx.doi.org/10.4028/www.scientific.net/amr.1125.387.

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The currently applied structure and fatigue assessment of support structure for offshore wind energy converter was based on common design rules. The accurate evaluation for environments of sea floor as to installation of support structure, loads of generator, dynamic loads in operation, and offshore environmental loads might be an essential requirement to acquire a safety design for the substructure. This study aims at dedicating to offshore-relevant technology fields by suggesting design methods of structures and estimating their safety in relation to the structural analysis of the substructure requiring high safety to various environment conditions. Especially, with respect to 5MW Offshore Wind Power System, this study will provide information about major wind directions and duration in combination with the developing wave climate at the test field. In this study in the dynamic analysis for 5MW offshore wind power substructure which is considered to be proper in Korea, it is expected that reliability of domestic technology is confirmed with respect to its structural stability.

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32

Carpenter, Chris. "Deepwater-Structure-Installation Challenges Offshore Australia". Journal of Petroleum Technology 69, nr 05 (1.05.2017): 50–52. http://dx.doi.org/10.2118/0517-0050-jpt.

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Murotsu, Y., M. Kishi, H. Okada, Y. Ikeda i S. Matsuzaki. "Probabilistic Collapse Analysis of Offshore Structure". Journal of Offshore Mechanics and Arctic Engineering 109, nr 3 (1.08.1987): 270–77. http://dx.doi.org/10.1115/1.3257020.

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This paper proposes a method for probabilistic collapse analysis of an offshore structure. Wave loads are estimated by using Stokes third-order theory and Morison’s formula. Plastic collapsing is evaluated by taking account of the combined load effect to generate the safety margins, using a matrix method. Probabilistically dominant collapse modes are selected through a branch-and-bound method. The proposed method is successfully applied to a jacket-type offshore platform.

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Frankel, Adam S., Mary Barkaszi, Jeffrey Martin, William Poe, Jennifer Giard i Ken Hunter. "Explosive offshore structure removal noise measurements". Journal of the Acoustical Society of America 141, nr 5 (maj 2017): 3848. http://dx.doi.org/10.1121/1.4988580.

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Zhang, Ruo Yu, Chao He Chen, You Gang Tang i Xiao Yan Huang. "Research Development and Key Technical on Floating Foundation for Offshore Wind Turbines". Advanced Materials Research 446-449 (styczeń 2012): 1014–19. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.1014.

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The water area in which water depth is deeper than 50m has special advantage in wind turbine generation, because there are the stable wind speed and small Wind-shear. In such sea area, the offshore wind energy generating equipments should be set up on floating foundation structure. Therefore, it is of great significance to study the floating foundation structures that are available for offshore wind energy generation for the industrialization of the offshore wind power generation. In this paper, the basic type and working principles are reviewed for some novel floating structures developed in recent year. In addition, some key dynamical problems and risk factors of the floating structure are systemically analyzed for working load caused by turbine running and sea environment loads of floating structure. The results are valuable for designing the floating structures of wind turbine generation.

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Ahmed, Mushtaq, Zafarullah Nizamani, Akihiko Nakayama i Montasir Osman. "Generation of Offshore Environments in the Numerical Wave Tank to Model Metocean Conditions Interaction with Offshore Structure Near the Free Surface". IOP Conference Series: Earth and Environmental Science 945, nr 1 (1.12.2021): 012018. http://dx.doi.org/10.1088/1755-1315/945/1/012018.

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Abstract Offshore structures play a vital role in the economy of offshore oil-producing countries, where mostly fixed jacket type structures are used to produce oil and gas installed in shallow water. In an offshore environment where structures are installed, there exist met ocean forces such as wind, waves, and currents. These met ocean conditions when interacting with offshore structures near the free surface, generate loads. The estimation of such loads is very much important for the proper design of these structures. The primary aim of this study is to investigate the interaction of waves with a jacket platform by generating offshore environments in the numerical wave tank (NWT). To achieve this goal, ANSYS Fluent is used for the flow analysis by using continuity and Navier Stokes equation. Results are verified and validated with the analytical work. Wave crests under operating condition generate a force of 1.3 MN which is the lowest in magnitude as compared to wave crest which produces 4.5 MN force under extreme conditions. Unlike operating wave crest, the operating wave trough generates a higher force of 1 MN than extreme conditions which account for 1.5 MN forces. Forces produced by the extreme offshore environment are 30% higher than those generated under operating conditions. It is concluded from the results that a positive force is exerted onto the structure during the water entry phase while a negative force is observed when the water leaves the structure.

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Chen, Junsheng, Chen Lin, Shuzhuo Liu i Haihong Mo. "Study on Supporting Structure Performance of Deep Soft Soil Foundation Pit near Sea under Waves, Tides, Vibration, and Unbalanced Loads". Advances in Civil Engineering 2020 (8.08.2020): 1–18. http://dx.doi.org/10.1155/2020/8830199.

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In addition to the vibration loads caused by offshore structure construction, the offshore foundation pit can also be affected by additional hydraulic loads such as waves, tides, and typhoons, hindering our understanding of the mechanical performance of the foundation pit supporting structure. In order to illuminate this mechanical performance under waves, tides, hammering, and unbalanced loads, this paper analyzed the supporting structure with theoretical and numerical simulations. The results were verified with field monitoring data. Moreover, the influences of loads, including construction vibration loads and unbalanced loads, on structure and soil were discussed. By applying these results to the engineering design, this research could provide a reference for studying mechanical properties of relevant supporting structures and the construction of offshore foundation pits.

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Newman, J. N., i C. H. Lee. "Boundary-Element Methods In Offshore Structure Analysis". Journal of Offshore Mechanics and Arctic Engineering 124, nr 2 (11.04.2002): 81–89. http://dx.doi.org/10.1115/1.1464561.

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Boundary-element methods, also known as panel methods, have been widely used for computations of wave loads and other hydrodynamic characteristics associated with the interactions of offshore structures with waves. In the conventional approach, based on the low-order panel method, the submerged surface of the structure is represented by a large number of small quadrilateral plane elements, and the solution for the velocity potential or source strength is approximated by a constant value on each element. In this paper, we describe two recent developments of the panel method. One is a higher-order method where the submerged surface can be represented exactly, or approximated to a high degree of accuracy by B-splines, and the velocity potential is also approximated by B-splines. This technique, which was first used in the research code HIPAN, has now been extended and implemented in WAMIT. In many cases of practical importance, it is now possible to represent the geometry exactly to avoid the extra work required previously to develop panel input files for each structure. It is also possible to combine the same or different structures which are represented in this manner, to analyze multiple-body hydrodynamic interactions. Also described is the pre-corrected Fast Fourier Transform method (pFFT) which can reduce the computational time and required memory of the low-order method by an order of magnitude. In addition to descriptions of the two methods, several different applications are presented.

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Wang, Na, Da Chen i Ying Di Liao. "Study on Foundation Structure for Comprehensive Power Generation of Offshore Renewable Energy". Advanced Materials Research 594-597 (listopad 2012): 121–25. http://dx.doi.org/10.4028/www.scientific.net/amr.594-597.121.

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The offshore renewable energy includes offshore wind, wave and tidal current energy. The power generation system of offshore renewable energy uses single form in recent year. It has caused low power efficiency, big power fluctuation and high cost of the foundation structure which will seriously hamper the development of offshore renewable energy. Firstly, a summary about the common form of foundation structure was made. Then basing on the different characteristics of a single energy power generation foundation structure, two different comprehensive power generation foundation types were put forward, and the power generation devices were optimized and reasonably arranged, which are formed a system for comprehensive offshore energy power generation. In addition, the connection, the load and structural features of each comprehensive power generation foundation structure were discussed. The results provide a basis for the design of foundation structure for comprehensive power generation of offshore renewable energy.

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Keys, Matt. "Offshore structures – why all offshore facilities should have a demanning requirement". APPEA Journal 59, nr 2 (2019): 789. http://dx.doi.org/10.1071/aj18109.

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Most offshore structure design codes focus on setting appropriate safety factors to achieve an acceptable annual level of risk. Recent work by Atkins SNC-Lavalin, together with a large number of operators in Australian waters and the North Sea, has discovered that a large number of aging assets are implementing a demanning requirement to limit the risk of platform collapse to personnel, due to changes in loading or degradation of the structure. This work has shown there are two risk scenarios that should drive this requirement. The first scenario which is intended by the codes in limiting the overall annual risk. The second is to limit the collapse risk associated with a known forecast storm, as the level of risk from helicopter demanning is much lower. For all the older offshore fixed and permanently mooring floating structures assessed for a risk level considered acceptable for a forecast storm, this risk level would govern the sea-state demanning criteria. For recently installed facilities that are compliant with current standards, the findings were the same: that all facilities should have a demanning requirement. The level of this demanning sea-state limit has been shown to be lower than expected and is likely to occur only once in the asset’s life; therefore, the cost implications of implementing demanning procedures are minor. This paper presents the basis and range of findings for calculating the risks associated with an annual occurrence and an ‘in a forecast storm’ risk. Further, this paper proposes acceptable demanning limits for facilities designed to current and historical design codes.

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Roni Sahroni, Taufik. "Modeling and Simulation of Offshore Wind Power Platform for 5 MW Baseline NREL Turbine". Scientific World Journal 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/819384.

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This paper presents the modeling and simulation of offshore wind power platform for oil and gas companies. Wind energy has become the fastest growing renewable energy in the world and major gains in terms of energy generation are achievable when turbines are moved offshore. The objective of this project is to propose new design of an offshore wind power platform. Offshore wind turbine (OWT) is composed of three main structures comprising the rotor/blades, the tower nacelle, and the supporting structure. The modeling analysis was focused on the nacelle and supporting structure. The completed final design was analyzed using finite element modeling tool ANSYS to obtain the structure’s response towards loading conditions and to ensure it complies with guidelines laid out by classification authority Det Norske Veritas. As a result, a new model of the offshore wind power platform for 5 MW Baseline NREL turbine was proposed.

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Chakrabarti, S. K. "Recent Advances in High-Frequency Wave Forces on Fixed Structures". Journal of Energy Resources Technology 107, nr 3 (1.09.1985): 315–28. http://dx.doi.org/10.1115/1.3231194.

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The computation of wave forces is one of the most vital tasks in the design of offshore structures. Many analytical tools are available for the determination of wave effects on offshore structures. These methods may be divided into two major categories: one for small members of an offshore structure and one for large members. A hybrid method is used for structures that have both types of members. The advances made in the last few years in the specific area of computing the high-frequency forces are reviewed here.

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Meyerhof, Geoffrey G. "Development of geotechnical limit state design". Canadian Geotechnical Journal 32, nr 1 (1.02.1995): 128–36. http://dx.doi.org/10.1139/t95-010.

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The historical development of limit state design in geotechnical engineering is reviewed. Total and partial factors of safety used for the design of land–based and offshore structures are compared. It is found that the factors of safety in different codes for the ultimate and serviceability limit states design of earthworks, earth retaining structures, and land-based and offshore foundations are very similar. Partial factors in the ultimate limit state design are linked to the variability of the loads and soil parameters, the design approximations, and construction tolerances. They influence the nominal probability of failure of the type of structure considered and the seriousness of failure, which differ for land-based and offshore structures. These probabilities are compared with human fatality risks of common experiences. The serviceability limit states are governed by structural and operational constraints and the intended service life of the land-based or offshore structure. The corresponding partial factors are generally taken as unity. Key words : codes, earth structures, foundations, human risks, limit states design, probability of failures, factors of safety.

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Lajimi, Mehdi, i Keyvan Sadeghi. "Examining the Effect of Angle of Regular Incident Wave in Deep Water on the Force on An Elliptical Vertical Cylinder Using FEM". Current World Environment 10, Special-Issue1 (28.06.2015): 21–26. http://dx.doi.org/10.12944/cwe.10.special-issue1.04.

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Today, a vast range of offshore structures is used in different parts of the world. Computing the force on an offshore structure is one of the first measures for designing the structure and also one of the most difficult steps in the design process. Most of offshore structures are considered as large structures. In these cases, it is used from diffraction theory for computing the imposed force. Using cylindrical elements is common in construction these structures. In this study, the effect of incident wave’s deviation angle on the force on the unit length of one elliptical vertical cylinder located within deep waters examined with finite element method. The obtained results show that the used numerical method had acceptable accuracy and the surge force on the vertical cylinder decreases with deviation angle increasing and consequently the sway force increases.

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Rueda-Bayona, Juan G., Andrés Guzmán i Andrés F. Osorio. "DOE-ANOVA for Identifying the Effect of Extreme Sea-States over the Structural Dynamic Parameters of a Floating Structure". Mathematical Modelling of Engineering Problems 9, nr 3 (30.06.2022): 839–48. http://dx.doi.org/10.18280/mmep.090334.

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Sea extreme events affect the integrity and operation of the offshore structures, then, it is important to analyze wind-waves-currents loads over the structural dynamics. Traditional offshore designing identifies structural parameters with certain limitations: physical modeling involves using shaking tables in dry conditions; numerical simulations have not sufficiently considered the effects of combined extreme waves-wind-current loads over the structure and the significance of the near and far hydrodynamic field over the structure. The non-linear interactions in the near hydrodynamic field generate viscous damping that modifies the dynamic structural parameters of the offshore structures. The traditional determination of structural parameters considers the hydrodynamic forces computed from wave records, omitting fluid-structure interactions that could generate unexpected damped periods and amplification peaks. This study applied physical modeling to determine floating structural parameters, considering combined loads and the effect of far and near hydrodynamic field in the fluid-structure interaction. The calculated transfer functions in the near hydrodynamic field revealed the highest amplification of the structural accelerations, and the transfer functions in the far field did not evidence structural resonance. Finally, this study recommends measuring the near hydrodynamic field and applying DOE-ANOVA for offshore designing to assess the viscous damping that may provoke dangerous structural amplifications.

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Wei, Shi Cheng, Bin Shi Xu, Xiu Bing Liang, Yu Jiang Wang i Yi Liu. "Research on Corrosion-Resistance of High Velocity Arc Spray Coatings on Surface of Steel Structure in Splash Zone Environment". Materials Science Forum 675-677 (luty 2011): 1291–94. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.1291.

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The most severe corrosion of offshore steel structure occurs in splash zone. There are many factors affecting the steel structure corrosion in the splash zone, such as corrosion problems caused by seawater and effect of impacted brought by the ocean wave. Considering the corrosion characteristics in splash zone and the corrosion invalidity behaviors of offshore steel structure, the Zn-15Al, Al-RE, Zn-Al-Mg-RE and FeBSiNb uncrystal coatings were prepared by automatic high velocity arc spraying. The different anti-corrosion behaviors of the four coatings were studied through the corrosion comparative tests and the microstructures analyzed of the coatings before and after the corrosion tests. The anti-corrosion coating systems suitable for using on surface of steel structure corrosion in the splash zone were found, which provided technique guarantee for extending the using life of offshore steel structures.

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Kim, Hyun-Gi, i Bum-Joon Kim. "Design Optimization of Conical Concrete Support Structure for Offshore Wind Turbine". Energies 13, nr 18 (17.09.2020): 4876. http://dx.doi.org/10.3390/en13184876.

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Various types of support structures for offshore wind turbine have been developed, and concrete structures have attracted attention due to many advantages. Although many studies have been conducted on the design of the existing steel structures, information and research on the design of concrete support structures are insufficient. Therefore, in this paper, a structural analysis model of conical concrete support structure (CCSS) is established and design optimization is presented. A detailed performance evaluation and the design of prestressed concrete were performed under the marine conditions of Phase 1 test site of southwest offshore wind project in Korea. The fluid–soil–structure interaction (FSI) was applied using the added mass method and soil spring model to represent the effects of water and soil. With the result of quasi-static analysis, a post-tensioning design was implemented by applying prestressing steel, and CCSS showed sufficient rigidity. From the natural frequency analysis, CCSS has a dynamic structural stability, and, in response spectrum and time-history analyses, the CCSS was safe enough under the earthquake loads. The methods and conclusions of this study can provide a theoretical reference for the structural analysis and design of concrete support structures for offshore wind turbines.

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Santosh Sawant, Sanket, i K. Dr. Muthumani. "Analysis of tubular joint of offshore structure". Journal of Physics: Conference Series 1716 (grudzień 2020): 012012. http://dx.doi.org/10.1088/1742-6596/1716/1/012012.

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Grewal, G. S., i M. M. K. Lee. "Ship impact on offshore minimum-structure platforms". Proceedings of the Institution of Civil Engineers - Engineering and Computational Mechanics 163, nr 1 (marzec 2010): 3–13. http://dx.doi.org/10.1680/eacm.2010.163.1.3.

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Goto, Masashi. "Accidents and Safety Issue of Offshore Structure". Journal of the Japan Institute of Metals 66, nr 12 (2002): 1215–26. http://dx.doi.org/10.2320/jinstmet1952.66.12_1215.

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