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Relevant bibliographies by topics / Offshore structure stability

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Academic literature on the topic 'Offshore structure stability'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 February 2022

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Journal articles on the topic "Offshore structure stability"

1

Pfoertner, Saskia, Hocine Oumeraci, Matthias Kudella, and Andreas Kortenhaus. "WAVE LOADS AND STABILITY OF NEW FOUNDATION STRUCTURE FOR OFFSHORE WIND TURBINES MADE OF OCEAN BRICK SYSTEM (OBS)." Coastal Engineering Proceedings 1, no. 32 (January 30, 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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Esmailzadeh, Ebrahim, and Avesta Goodarzi. "Stability analysis of a CALM floating offshore structure." International Journal of Non-Linear Mechanics 36, no. 6 (September 2001): 917–26. http://dx.doi.org/10.1016/s0020-7462(00)00055-x.

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Van den Abeele, F., and J. Vande Voorde. "Stability of offshore structures in shallow water depth." International Journal Sustainable Construction & Design 2, no. 2 (November 6, 2011): 320–33. http://dx.doi.org/10.21825/scad.v2i2.20529.

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The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.

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Subcommittee on Wave-Seabed-Structu. "Stability of Foundation of Coastal and Offshore Structure Under Waves." Doboku Gakkai Ronbunshu, no. 539 (1996): 1–13. http://dx.doi.org/10.2208/jscej.1996.539_1.

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Sun, Min Young, Ki Yeol Lee, and Byung Young Moon. "A Study on the Structural Analysis of Jacket Substructure Related to Offshore Wind Power Environment." Advanced Materials Research 1125 (October 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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Dong, Ji Wu, Zhi Jun Li, Li Min Zhang, Guang Wei Li, and Hong Wei Han. "Experimental Study of Sea Ice Forces on a Structure and its Stability." Advanced Materials Research 243-249 (May 2011): 4750–53. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4750.

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A structure was designed to reduce the large forces exerted by level ice on offshore structures in shallow icy waters, by breaking the large ice floes into small pieces from flexing-induced failure. A series of model tests was conducted to simulate ice loads on the structure. A concrete model of it was adopted to verify the stability of the structure under the action of ice floes, which had five different thicknesses. The results show that ice forces on the structure are low and that the stability of the structure under different sea bed is good.

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Kim, Hyun-Gi, and Bum-Joon Kim. "Design Optimization of Conical Concrete Support Structure for Offshore Wind Turbine." Energies 13, no. 18 (September 17, 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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Ju, G. T., and S. Kyriakides. "Thermal Buckling of Offshore Pipelines." Journal of Offshore Mechanics and Arctic Engineering 110, no. 4 (November 1, 1988): 355–64. http://dx.doi.org/10.1115/1.3257073.

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The vertical buckling of offshore pipelines caused by thermal loads is analyzed by modeling the pipeline as a long heavy beam resting on a rigid foundation. The axial restraint provided to the line by the surrounding soil is modeled as Coulomb friction. The study is concerned with the effect of localized, small initial geometric imperfections on the response and stability of the structure. In the presence of initial imperfections, the response is characterized by the temperature rise required to cause initial uplift and by a limit temperature rise beyond which the structure becomes unstable. Both of these critical values are shown to be sensitive to the form and magnitude of the imperfections as well as by the pipe material inelastic characteristics.

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Gao, Rui, Ling Qiang Yang, and Yan Wang. "Analysis of Gravity Foundation for Offshore Structure under Cyclic Loads." Applied Mechanics and Materials 580-583 (July 2014): 2177–80. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.2177.

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Cyclic characteristic of offshore environmental load may cause the accumulation of foundation settlement and excess pore pressure in the subsoil. This may lead to conditions that jeopardize the structural stability and operability of the wind turbine. This paper discusses the analysis steps of the responses of non-cohesive subsoil under cyclic loads for a gravity base foundation system.

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Dymarski, Paweł, Czesław Dymarski, and Ewelina Ciba. "Stability Analysis of the Floating Offshore Wind Turbine Support Structure of Cell Spar Type during its Installation." Polish Maritime Research 26, no. 4 (December 1, 2019): 109–16. http://dx.doi.org/10.2478/pomr-2019-0072.

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Abstract The article presents the results of selected works related to the wider subject of the research conducted at the Faculty of Ocean Engineering and Ship Technology of the Gdansk University of Technology, which concerns design and technology of construction, towing, and settlement on the seabed, or anchoring, of supporting structures for offshore wind farms. As a result of this research, several designs of this type of objects were developed, including two stationary types: gravitational and Jack-up, which are placed on the seabed, and two floating types: TLP and SPAR, anchored with tendons and anchors in the form of nailed or suction piles. Below presented is the stability analysis of the new floating CELL SPAR type support structure for offshore wind turbines during its installation in waters with a depth of over 65 m.

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Dissertations / Theses on the topic "Offshore structure stability"

1

Konstantopoulos, G. P. "A unified treatment of semisubmersible stability." Thesis, University of Strathclyde, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382306.

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Liedtke, Eric Arthur. "Effects from uncertainties in bathymetric measurements and variability in topography on computed stability of offshore slopes in deep water /." Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008380.

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Neto, Alfredo Gay. "Estabilidade estrutural da configuração estática de risers em catenária." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-15072013-163230/.

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Risers em configuração de catenária podem apresentar nível de tração muito baixo próximos ao fundo do mar. Isso pode ocorrer em algumas condições de lançamento, em que sua estrutura pode se configurar de forma quase vertical. Quando se trata de tubos flexíveis ou cabos umbilicais, a composição interna do riser contém armaduras helicoidais de tração. Essas podem induzir a ocorrência de giro axial quando o tubo é solicitado à tração. Se esse movimento não for permitido, surgirá um momento de torção na estrutura. O baixo nível de tração da configuração de catenária combinado com o momento de torção surgido durante o lançamento do riser pode levar a uma forma de instabilidade estrutural que culmina na formação de um laço. Isso é indesejável uma vez que, se existe o laço, dependendo dos esforços submetidos à linha, é possível que o laço se transforme em uma dobra, danificando a estrutura. O presente trabalho analisa as condições de formação de laços em configurações de catenária. Para isso, foram utilizados critérios de estabilidade aplicados a um modelo de elementos finitos, que leva em conta as não linearidades geométrica e de contato entre o riser e o solo. Foi utilizada uma formulação cinematicamente exata de elemento de viga através de uma descrição lagrangiana atualizada, que pode tratar de forma correta as grandes rotações que são impostas ao riser para induzir o surgimento do momento de torção. É mostrado que uma expressão analítica baseada na Fórmula de Greenhill pode prever o fenômeno com boa concordância com os resultados numéricos, mesmo considerando-se fenômenos como contato unilateral com atrito e correntezas marítimas. Além disso, foi feita uma análise paramétrica para prever a formação do laço para diversas geometrias de catenária, procurando generalizar as conclusões obtidas.
Catenary risers can show a very low tension level close to the seabed. This can occur in some launching conditions, in which the structure can be almost vertical. When dealing with flexible pipes or umbilical cables, their internal composition includes the helical tension armors. These can induce an axial rotation to the riser when it is tensioned. If this movement is constrained, a torsion moment will act upon the structure. The low tension level present in the catenary configuration combined with the torsion moment that occurs during the riser launching can lead to a structural instability, resulting in a loop formation. This is undesirable since, if the loop is present, depending on the loads applied to the riser it is possible that it turns into a kink, causing damage. The present work analyzes the loop formation conditions in catenary riser. For that, stability criteria were applied to a finite element model that takes into account the geometric nonlinearities and also the contact between the riser and the seabed. A kinematically-exact beam formulation was adopted, dealing correctly with the large rotations that are imposed to the riser, in order to induce the torsion moment. It is showed that an analytical expression based on Greenhills formula can predict the phenomenon with a good agreement with numerical results, even including phenomena as frictional unilateral contact and sea currents. Furthermore, a parametric analysis was done to predict the loop formation to some catenary geometries, in order to generalize the obtained conclusions.

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Quéméneur, Philippe. "Caractérisation géotechnique en zone d"offshore" profond et analyse régionale de la stabilité des pentes : application à quelques secteurs de la pente continentale du golfe de Guinée." Vandoeuvre-les-Nancy, INPL, 1996. http://www.theses.fr/1996INPL073N.

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Deux campagnes océanographiques ont été réalisées en 1992 et 1993 par Ifremer and Elf Aquitaine Production, dans le golfe de Guinée, avec des prélèvements de carottes küllenberg et l'acquisition de données géophysiques par grandes profondeurs d'eau. Les essais géotechniques, réalisés au laboratoire de géotechnique de l'E. N. S. G. , ont permis une description synthétique des sédiments superficiels sur les talus continentaux du Nigeria, du Gabon et du Congo. Sur la pente continentale du Gabon, ces résultats mettent en évidence un état sous-consolidé en profondeur. Les relevés géophysiques y indiquent l'existence de figures d'expulsion de fluides et de zones de sédiments superficiels chargés en gaz. Un réflecteur acoustique profond de trente mètres est interprété comme une surface de glissement potentiel, ou le facteur de sécurité non drainé semble à un minimum. La prise en compte de la bathymétrie et des critères de stabilité ont permis une cartographie régionale du risque et une interprétation des désordres identifies par la géophysique: les résultats confirment que ces désordres correspondent à un état remanié en profondeur ou à la migration de fluides interstitiels ; nous avons calibré l'impact de différents modes d'action des fluides interstitiels sur la stabilité des sédiments. Les essais géotechniques ont donc apporté une caractérisation systématique et synthétique des sédiments prélevés dans le golfe de Guinée. La juxtaposition d'informations géophysiques et géotechniques a permis d'inventorier, de calibrer et de localiser les causes de désordres dans la zone Gabon ; toutefois, une meilleure connaissance des processus gravitaires dans cette zone passerait par l'étude locale des phénomènes identifiés et l'acquisition de mesures in situ: mesures de la fraction gazeuse, des excès de pression interstitielle et des contraintes effectives verticales

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Manco, Tiago Jorge da Cruz. "Avaliação comparativa da regulamentação para estruturas offshore (API, ISO, NORSOK, EC3)." Master's thesis, 2014. http://hdl.handle.net/10316/38547.

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Dissertação de Mestrado Integrado em Engenharia Civil apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
O objectivo da presente tese é efectuar uma análise comparativa da regulamentação para estruturas offshore, especificamente ao nível do dimensionamento de elementos tubulares circulares em aço. Para tal, serão inicialmente comparadas ao nível da formulação e procedimento de cálculo, normas específicas para estruturas offshore, nomeadamente a API, ISO e NORSOK juntamente com o Eurocódigo 3 que é uma norma que não contém provisões específicas para este tipo de estruturas. Seguidamente, pretende-se aferir a capacidade resistente destes elementos, de forma detalhada através de um estudo paramétrico abrangente, quer para esforços isolados quer para esforços combinados. Neste caso, a atenção será concentrada na ISO e no EC3. Com isto, objectiva-se tirar conclusões do nível da segurança que estes dois conjuntos de normas (normas de estruturas offshore vs normas de construção) apresentam, identificando diferenças ao nível da formulação, procedimentos e resistência de elementos tubulares circulares. Relativamente ao Eurocódigo 3 será feito uso da parte 1-1 e da parte 1-6 (elementos do tipo casca), para que todas as classes de secções possam ser abrangidas, visto esta gama de secções estar habitualmente presente em estruturas desta natureza. Este aspecto será aproveitado para avaliar os resultados obtidos na transição da classe 3 para a classe 4, tratadas por partes e procedimentos de cálculo distintos. O facto de o Eurocódigo não estar desenvolvido para aplicação em estruturas offshore limita a aplicação a algumas situações nomeadamente, a não consideração da pressão hidrostática na parte 1-1. Por fim, será levada a cabo uma análise numérica recorrendo ao método dos elementos finitos (através do software ABAQUS) para aferir o conservadorismo que cada norma (ISO e EC3) tem inerente a si. Para tal serão avaliados isoladamente e em interacção os outros de esforços de compressão e pressão hidrostática.
The objective of the present thesis is to perform a comparative analysis of the design standards in offshore structures, especially in the design of circular tubular elements. To this end, it will be initially compared, in the formulation and calculation procedure, specific offshore standards namely the API, ISO and NORSOK with the Eurocode 3 that does not contain specific provisions for this type of structures. Subsequently, it is intended to assess the bearing capacity of these elements in detail through a broad parametric study, in the presence of isolated and combined loadings. In this case, attention will be concentrated in ISO and EC3. With this, the objective is to draw conclusions regarding the safety that these two sets of standards (offshore standards vs. construction standards) present, identifying differences in the formulation, procedures and strength of circular tubular elements. With respect to Eurocode 3 will be made use of the part 1-1 and part 1-6 (shell elements), in order to cover all classes of sections, since this range of sections is usually present in structures of this kind. This will be used to assess the results obtained in the transition from class 3 to class 4, treated by different parts and calculation procedures. The fact that the Eurocode was not developed for the application in offshore structures limits the application to some situations, namely the lack of consideration of hydrostatic pressure on the part 1-1 of this standard. Finally, it will be carried out a numerical analysis using the finite element method (through the ABAQUS software) to evaluate the conservatism that each standard (ISO and EC3) has inherent to itself. To this will be evaluated alone and in interaction the axial compression and the hydrostatic pressure.

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Books on the topic "Offshore structure stability"

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International Conference on Fatigue and Crack Growth in Offshore Structures (1986 London, England). International Conference on Fatigue and Crack Growth in Offshore Structures. London: The Institution of Mechanical Engineers, 1986.

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2

Carr, Peter. Development of a method to make use of sensitivity studies and its application to analysis of uncertainties in environmental loading on offshore structures. London: H.M.S.O., 1989.

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Advanced stability. Austin, Tex: University of Texas at Austin, Petroleum Extension Service, 2005.

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Advanced Stability. University of Texas Press, 2006.

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Lin, Huan. Chaotic response and stability of offshore equipment. 1990.

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Chengi, Kuo, University of Strathclyde, Society for Underwater Technology, and Royal Institution of Naval Architects., eds. Stationing and stability of semi-submersibles. London, UK: Graham & Trotman, 1986.

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P, Le Tirant, and Pérol Christian, eds. Stability and operation of jackups. Paris: Editions Technip, 1993.

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International Conference on Fatigue and Crack Growth in Offshore Structures: 7-8 April 1986, the Institution of Mechanical Engineers, Birdcage Wal. Amer Society of Mechanical, 1986.

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Book chapters on the topic "Offshore structure stability"

1

Oumeraci, Hocine, Saskia Pfoertner, Matthias Kudella, and Andreas Kortenhaus. "Ocean Brick System (OBS) as a foundation structure for offshore wind turbine - An experimental study for wave loads and stability." In Coasts, marine structures and breakwaters: Adapting to change, 2: 74–85. London: Thomas Telford Ltd, 2010. http://dx.doi.org/10.1680/cmsb.41318.0008.

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van Santen, Joost. "The Use of Energy Build Up to Identify the Most Critical Heeling Axis Direction for Stability Calculations for Floating Offshore Structures." In Fluid Mechanics and Its Applications, 193–216. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-1482-3_10.

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Hazarika, H. "An interaction model for seismic stability analysis of caisson type structure." In Frontiers in Offshore Geotechnics. Taylor & Francis, 2005. http://dx.doi.org/10.1201/noe0415390637.ch62.

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"Offshore Structures (近海結構)." In Plasticity, Limit Analysis, Stability and Structural Design, 256–78. WORLD SCIENTIFIC, 2021. http://dx.doi.org/10.1142/9789811229749_0009.

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Dewoolkar, M., H. Ko, and J. Hwang. "Lateral stability of offshore skirted gravity structures." In Physical Modelling in Geotechnics. Taylor & Francis, 2006. http://dx.doi.org/10.1201/noe0415415866.ch90.

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Conference papers on the topic "Offshore structure stability"

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Christiansen, P. E., S. M. Komaromy, J. Dolwin, and E. Piermattei. "A Dynamic Analysis Method For Structure On-Bottom Stability." In Offshore Technology Conference. Offshore Technology Conference, 1986. http://dx.doi.org/10.4043/5178-ms.

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Jung, Minuk, and Keum-Seok Kang. "Floating Stability During Installation of Gravity Base Structures." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62287.

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In order to obtain more wind energy, offshore wind farms tend to be constructed in deeper water with larger wind turbines. Various kinds of support structures, including gravity base structures, are considered to reduce the CAPEX of wind farms. In this paper, feasibility of floated gravity base structures is investigated through floating stability analysis on lowering operations during the installation. In regard to the baseline model for 30 m water depth with the spherical base and the top diameter of 6 m, the floating stabilities are derived by varying the base diameter and the draft. As it is assumed that the structures are ballasted with sea water during the installation step, free surface effects are taken into account. The relevant structures satisfying the floating stability requirement are derived. It is shown that the structure should be equipped with the bulkheads to satisfy this requirement. Furthermore, the geometry of gravity base structure which minimize the weight of the structure is investigated.

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Abdalla, Basel, F. Steven Wang, and M. Kabir Hossain. "FEA-Based Stability Analysis of Mudmats: Coupled Soil-Structure-Flowline Interaction Model." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10955.

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The traditional method of foundation stability assessment for subsea structures is to calculate the bearing capacity factor of safety using classical approach given in the API-RP-2A/2GEO. This classical approach can be overly conservative for foundations under complex loading conditions (e.g., multiple interacting loads). A typical example is pipeline end manifold or flowline sled, which can be subject to self-weight, structure-soil interaction, and multiple interface loads from flowline and jumpers under operational condition. A more rigorous 3D-FEA based assessment approach is developed in this paper to achieve more accurate bearing capacity estimates for a flowline sled supported by mudmat. This fully combined global model comprises the structure (with sliding mechanism), soil foundation, jumpers, and flowline as realistically as possible so as to capture the more accurate interactions among the different parts of whole sled-soil system. The use of such advanced numerical modeling has proven to improve the mudmat bearing capacity factor of safety.

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Feng, Yan, Hui Li, Chenfeng Li, Junjie Ruan, Qiyou Zhang, and Weijun Xu. "Investigation on the Structure Strength and Stability of Ring Stiffened Cylindrical Shell With Long Compartment and Large Stiffener." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62153.

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With the increasing status of the sea, the research and manufacture of submersible vessel will be paid more attention. In order to enlarge the submergence depth and utilization efficiency of submersible vessel space, long compartment structures of high strength steels and in various forms are widely adopted. The strength problem of such structure is easy to be guaranteed, while the resulting stability problem is becoming more and more serious. For a ring-stiffened cylindrical shell structure with long compartment, one or two large stiffeners are used on the shell structure to ensure its overall stability. This paper studies the strength and stability of the long compartment cylindrical shell structure, with a special emphasis on the stability problems of overall long compartment structures and large stiffeners. The failure modes and critical load under deep water are analyzed by a theoretical method and also a finite element method. The formula for calculating the large stiffener of submersible vessel structure is derived based on the theory of elastic mechanics, and the defect and deficiency of the formula used in the current design specification is pointed out. The influence of large stiffener position and structure form on the critical pressure of submersible cylindrical shell structure is studied. The results of theoretical analysis and numerical simulation are also compared and discussed.

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Hazarika, Hemanta. "On Stability Improvement of Gravity Type Onshore and Offshore Structures." In ASME 2005 24th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2005. http://dx.doi.org/10.1115/omae2005-67283.

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A protective cushion layer sandwiched between a gravity type caisson and the surrounding soil can improve the seismic stability of the caisson. In this paper, an interaction model was developed for analyzing such structure under earthquake loading. Interfaces on either side of the cushion were modeled as elements of finite thickness having different stiffness and constitutive properties. Participation from each element of the interaction system was taken into the account by incorporating appropriate factors at the respective interfaces. Seismic analyses were performed on a gravity-type caisson subjected to an actual earthquake motion. Comparison of the analysis results with a similar caisson without any protective cushion showed that the use of cushion yields a significant reduction of seismic load on the structure.

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Jaiman, Rajeev K., Farzin Shakib, Owen H. Oakley, and Yiannis Constantinides. "Fully Coupled Fluid-Structure Interaction for Offshore Applications." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79804.

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CAD integrated tools are accelerating product development by incorporating various aspects of physics through coupling with computational aided engineering (CAE) packages. One of the most challenging areas is fluid-structure interaction (FSI) of low mass bodies such as flexible marine risers/cables with vortex-induced vibrations. The focus of this work is on the application of a new Multi-Iterative Coupling (MIC) procedure to couple AcuSolve (fluid solver) with Abaqus (structural solver). The proposed new scheme has superior stability and convergence properties as compared to conventional explicit staggered schemes, especially for low mass-density ratios of structure to fluid. Demonstrations and validation of the scheme are presented and discussed along with additional challenges associated with FSI in production environments. The addition of an FEA solver enables the modeling of the nonlinear aspects of flexible riser VIV, namely, contacts with gaps, multi-body dynamics, seabed interaction, geometric and/or material nonlinearities.

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Bubel, Julian, Christina Rudolph, and Ju¨rgen Grabe. "Stability of Temporary Submarine Slopes." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-50157.

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Shallow foundation structures for offshore wind turbines offer ecological benefits compared to pile foundations as less noise is emitted at sea floor level during construction process. On the other hand, shallow offshore foundations can rarely be placed on top of the sea floor. Weak soils usually need to be excavated to place the foundation structure on more stable ground and thus, anthropogenic submarine slopes result. Steep but stable slopes meet both economic and ecologic aims as they minimise material movement and sediment disturbance. After Terzaghi [1] the angle β between slope and the horizontal of the ground surface of coarse-grained soil is at most equal to the critical state friction angle φc. However, it can be observed that natural submarine slopes of sandy soils are always much more shallow. Particularly fine-grained, cohesionless or almost cohesionless soils failed in the past, although the slope angle was much smaller than the critical state friction angle φc. Artificial (temporary) slopes do not appear and behave as natural submarine slopes, since the latter are already shaped by perpetual loads of waves, tide and mass movements. Physical simulations of different scales are used to analyse the stability of artificial submarine slopes with sandy soil of the North Sea. The study focuses on gravitational forces and impacts from the excavation processes. The simulations and theoretical considerations result in suggested slope angles for future shallow offshore foundations of wind farms in the North Sea.

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Ma, Leixin, Shixiao Fu, Ke Hu, Qian Shi, and Runpei Li. "Investigation Into Stability and Accuracy in Predicting Slender Bodies’ Hydroelasticity Using Loose Coupling Methods." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41136.

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Problems concerning fluid-structure-interaction are often encountered in aquaculture engineering. For a moving slender structure like fishing net or floater in currents and waves, modified Morison Equation is a widely employed formula to estimate its hydrodynamic loads. The hydrodynamic forces are closely dependent on the structures’ velocity and acceleration, and quadratic relative velocity in the equation even adds nonlinearity in the forces. To study the hydroelastic response, two time-saving loosely coupling methods, calculating the hydrodynamic forces based on the structure’s response in the previous time step without iteration, are proposed in this paper. The loose coupling methods were proved to affect the traditional stability criteria for time integration. Based on the two loose coupling methods, the stability and accuracy of a slender beam’s hydroelasticity undergoing large deformation were studied. The calculated responses were compared against strong coupling results. It was found that if loose coupling is assumed in added mass force, unconditional instability is likely to occur. On the other hand, the accuracy of numerical results can be improved with smaller time increments set if loose coupling is only assumed in the quadratic relative drag force.

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Feng, Dianshi, Sze Dai Pang, and Jin Zhang. "Parameter Sensitivity in Numerical Modelling of Ice-Structure Interaction With Cohesive Element Method." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54687.

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The increasing marine activities in the Arctic has resulted in a growing demand for reliable structural designs in this region. Ice loads are a major concern to the designer of a marine structure in the arctic, and are often the principal factor that governs the structural design [Palmer and Croasdale, 2013]. With the rapid advancement in computational power, numerical method is becoming a useful tool for design of offshore structures subjected to ice actions. Cohesive element method (CEM), a method which has been widely utilized to simulate fracture in various materials ranging from metals to ceramics and composites as well as bi-material systems, has been recently applied to predict ice-structure interactions. Although it shows promising future for further applications, there are also some challenging issues like high mesh dependency, large variation in cohesive properties etc., yet to be resolved. In this study, a 3D finite element model with the use of CEM was developed in LS-DYNA for simulating ice-structure interaction. The stability of the model was investigated and a parameter sensitivity analysis was carried out for a better understanding of how each material parameter affects the simulation results.

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Bubel, Julian, and Jürgen Grabe. "Stability of Submarine Foundation Pits Under Wave Loads." In ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/omae2012-83027.

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Abstract:

Shallow foundation structures offer ecological benefits compared to pile foundations as less noise is emitted at sea floor level during construction process. On the other hand, shallow offshore foundations can rarely be placed on top of the sea floor. Weak soils usually need to be excavated to place the foundation structure on more stable ground and thus, anthropogenic submarine pits result. Steep but stable slopes of the pit meet both economic and ecologic aims as they minimise material movement and sediment disturbance. According to Terzaghi [1] the angle β between slope and the horizontal of the ground surface of cohesionless soil is at most equal to the critical state friction angle φc. However, it can be observed that natural submarine slopes of sandy soils are always much more shallow. Artificial (temporary) slopes do not appear and behave as natural submarine slopes, since the latter are already shaped by perpetual loads of waves, tide and mass movements. Physical simulations of different scales were presented at the OMAE 2011 [2] to analyse the stability of artificial submarine slopes of sandy soil in the North Sea. The laboratory tests focused on gravitational forces and impacts from the excavation processes. This paper presents additional numerical simulations of wave-induced bottom pressure on the suggested submarine foundation pits. Furthermore, in-situ tests will be performed in 2012 and 2013. Both dredging process and resulted foundation pits will be considerably surveyed.

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