offshore structures thesis

Floating Architecture and Conversion of Offshore Structures: A Chronicle of Knud E. Hansen Designs

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• Carmelo Cascino 12 , 13 &
• Francesca Arini 13  

Part of the book series: Lecture Notes in Civil Engineering ((LNCE,volume 158))

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Alteration of the physical environment, and the scarcity of land for urban growth in proximity of the coast as well as rising sea levels are endangering the prosperity of entire communities around the world. These represent some of the major challenges our society will be facing in the near future. However, water can also provide alternative scenarios for human habitability. In this regard, floating structures appear as a realistic solution to adapt to the ongoing transformations. Although projects on water, ranging from a single building to entire neighborhoods, have increased significantly in the last decade, thanks to technological advancement, visions of water civilizations have been around since approximately 1950, when research in this field was undertaken for military and economic purposes. Therefore, interest in buoyant structures has appeared from time to time. It was during the 80s that the Danish ship design firm Knud E. Hansen was involved by a visionary entrepreneur in a project of conversion of an offshore platform into a luxury resort. This experience emphasized the multidisciplinary nature of floating structures in a hybrid of naval engineering and civil architecture.

• Buoyant structures
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• Sustainability
• Hospitality

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Acknowledgements

We would like to thank Christine Harris, Finn Wollesen Petersen, Morten Skrydstrup, Ole Olsen and Tristan Andrewartha for their assistance.

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University of Genoa, Genoa, Italy

Carmelo Cascino

Knud E. Hansen, 67 Akti Miaouli Str, 11537, Pireas, Greece

Carmelo Cascino & Francesca Arini

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Floating Solutions LLP, Singapore, Singapore

Soon Heng Lim

School of Civil Engineering, The University of Queensland, Brisbane, QLD, Australia

Chien Ming Wang

Rotterdam University of Applied Sciences, Rotterdam, The Netherlands

Rutger de Graaf-van Dinther

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Cascino, C., Arini, F. (2022). Floating Architecture and Conversion of Offshore Structures: A Chronicle of Knud E. Hansen Designs. In: Piątek, Ł., Lim, S.H., Wang, C.M., de Graaf-van Dinther, R. (eds) WCFS2020. Lecture Notes in Civil Engineering, vol 158. Springer, Singapore. https://doi.org/10.1007/978-981-16-2256-4_5

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Numerical investigation of freak wave effects on offshore structures

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• Sun, Mengshi.
• Strathclyde Thesis Copyright
• University of Strathclyde
• Doctoral (Postgraduate)
• Doctor of Philosophy (PhD)
• Department of Naval Architecture, Ocean and Marine Engineering.
• The freak wave is extremely dangerous to offshore structures due to its unexpected high wave height and strong nonlinearity. Although increasingly more attention is paid to the investigations of freak wave, the principle of its generation mechanism and the factors that contribute to its occurrence remain unclear. Also, few efforts were exerted to investigate the interactions between offshore structures and a freak wave such as wave run-up and slamming force. In this present work, both the two dimensional (2D) and three dimensional (3D) numerical wave tanks are established based on Navier-Stokes equations for viscous, incompressible fluid by CFD commercial software FLUENT.;At first, the regular waves are generated numerically. Two different wave generation methods, paddle wave making method and the source function wave making method, are introduced. The paddle wave-making method is a physical wave generation technology which is to imitate the wave makers in the laboratory. The source function wave-making method is discussed later and the empirical formulas of the source size and source intensity are introduced. The numerical wave elevations are compared with the linear analytical results.;Second, the freak waves are generated numerically. According to Longuet-Higgins wave model theory, the wave free surface can be represented by the linear sum of the individual wave components with different frequencies and random phases. Improving this wave model, the wave components have their phase adjusted, so that a large amount of energy is located at the focus position at a given time. Then two more efficient and realistic freak wave models are presented, combining wave models and phase modulation wave models, respectively. Finally, the numerical results of the shift of freak wave train focusing position and focusing time are analysed, and the time history of wave elevations are compared with the analytical results.;Third, a 3-D numerical wave tank is established to perform the interactions between a freak wave train and a single cylinder or a pair of two cylinders. How the focused wave parameters, including wave steepness, frequency bandwidth, focused position and the distance between the two cylinders, affect the freak wave run-up and total slamming forces on the cylinders are investigated.;Finally, the hydrodynamic behaviour of a rectangular body in roll motions under both freak wave excitation and internal flow sloshing is investigated in a CFD numerical wave tank. In this study, three different freak wave conditions are considered, and two different water levels are investigated.;The comparisons of numerical regular wave elevations and first order analytical results show that the current CFD numerical wave tank based on computational fluid dynamic commercial software FLUENT has a good capacity in sea water waves simulation. The focused wave parameters, such as frequency bandwidth and input wave steepness, have an obvious effect on the nonlinear behaviour of a focused wave group.;This nonlinear behaviour will not only downstream shift the focused position and focused time, but also change the wave elevation at the focused position largely. The increased nonlinear behaviour of a focused wave group will increase the wave run-up along a fixed vertical cylinder at the incident wave facing direction largely. The bigger nonlinear behaviour of a focused wave group can result in larger rolling motion amplitude for a floating rectangular body, however the anti-rolling behaviour is obvious for the low filling case.
• Doctoral thesis
• 10.48730/d722-0p59
• 9912549492602996

• About DTU Orbit

Efficient computations of wave loads on offshore structures

Research output : Book/Report › Ph.D. thesis

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• Calculation Physics 100%
• Impact Physics 100%
• Domains Physics 83%
• Directional Engineering 50%
• Circular Cylinder Engineering 50%
• Load Cycle Engineering 50%
• Steepness Engineering 50%
• Cycles Physics 50%

Projects per year

Efficient CFD computation of extreme wave loads on wind turbine foundations

Paulsen, B. T., Bingham, H. B. , Bredmose, H. , Christensen, E. D. , Grue, J. & Yeung, R. W.

Institut, samfinansiering

01/09/2010 → 22/11/2013

Project : PhD

• Impact 100%
• Calculation 100%
• Domains 83%
• Load Cycle 50%
• Steepness 50%

T1 - Efficient computations of wave loads on offshore structures

AU - Paulsen, Bo Terp

N2 - The present thesis considers numerical computations of fully nonlinear wave impacts on bottom mounted surface piercing circular cylinders at intermediate water depths. The aim of the thesis is to provide new knowledge regarding wave loads on foundations for offshore wind turbines. Hence, the dimensions of the cylinders and the chosen wave parameters were inspired by typical monopile foundations for offshore wind turbines.The numerical computations are carried out using three numerical solvers. That is, the fully nonlinear Navier-Stokes/VOF solver provided as a part of the open-source CFD-toolbox OpenFoam R, the fully nonlinear potential flow solver OceanWave3D and finally a fully nonlinear domain decomposed solver, which was developed as part of this project. In the domain decomposed solver, the outer wave field is described by the potential flow solver, whereas the inner wave field, in the vicinity of a given structure, is described by the Navier-Stokes/VOF solver.All numerical models are carefully validated either in terms of convergence by grid refinement or by comparisons to experimental measurements. Special attention is paid to the newly developed domain decomposed solver, which is carefully validated against experimental measurements of regular-, irregular- and multi-directional irregular waves. The ability of the numerical model to accurately reproduce experiments is also investigated.Wave impacts on a bottom mounted circular cylinder from steep regular waves are presented. Here, the inline forces and the motion of the free surface is described as a function of the non-dimensional wave steepness, the relative water depth, the relative cylinder diameter and a co-existing current. From the computations, higher harmonic forces are determined and compared against the Morison equation and established analytical force formulations accurate to the third order in wave steepness.The physics related to the strongly nonlinear load phenomena “secondary load cycles” is described and an explanation of the wave load phenomena is provided. To further support the explanation a simple inviscid kinematic model flow is derived.The discussion of wave impacts on circular cylinders is further extended to uni- and bi-directional phase-focused waves. Here, the influence of the nondimensional wave steepness and wave directionality is discussed. For the steepest wave impacts “secondary load cycles” are observed and the physics of the impact and the mechanisms related to the “secondary load cycle“ are discussed and compared to the observations made for regular waves.Additionally, attention is paid to experimental determination of hydrodynamic forces. Significant differences between experimentally measured and computed higher harmonic forces are observed and the differences are explained in terms of the eigenmotion of the test setup. Finally, the application of the domain decomposed solver is discussed in an engineering context. Here, a simple and robust way of identifying forces, which may be inaccuvii rately estimated by the Morison equation, is presented. It is suggested that these impacts are recomputed by the domain decomposed solver.

AB - The present thesis considers numerical computations of fully nonlinear wave impacts on bottom mounted surface piercing circular cylinders at intermediate water depths. The aim of the thesis is to provide new knowledge regarding wave loads on foundations for offshore wind turbines. Hence, the dimensions of the cylinders and the chosen wave parameters were inspired by typical monopile foundations for offshore wind turbines.The numerical computations are carried out using three numerical solvers. That is, the fully nonlinear Navier-Stokes/VOF solver provided as a part of the open-source CFD-toolbox OpenFoam R, the fully nonlinear potential flow solver OceanWave3D and finally a fully nonlinear domain decomposed solver, which was developed as part of this project. In the domain decomposed solver, the outer wave field is described by the potential flow solver, whereas the inner wave field, in the vicinity of a given structure, is described by the Navier-Stokes/VOF solver.All numerical models are carefully validated either in terms of convergence by grid refinement or by comparisons to experimental measurements. Special attention is paid to the newly developed domain decomposed solver, which is carefully validated against experimental measurements of regular-, irregular- and multi-directional irregular waves. The ability of the numerical model to accurately reproduce experiments is also investigated.Wave impacts on a bottom mounted circular cylinder from steep regular waves are presented. Here, the inline forces and the motion of the free surface is described as a function of the non-dimensional wave steepness, the relative water depth, the relative cylinder diameter and a co-existing current. From the computations, higher harmonic forces are determined and compared against the Morison equation and established analytical force formulations accurate to the third order in wave steepness.The physics related to the strongly nonlinear load phenomena “secondary load cycles” is described and an explanation of the wave load phenomena is provided. To further support the explanation a simple inviscid kinematic model flow is derived.The discussion of wave impacts on circular cylinders is further extended to uni- and bi-directional phase-focused waves. Here, the influence of the nondimensional wave steepness and wave directionality is discussed. For the steepest wave impacts “secondary load cycles” are observed and the physics of the impact and the mechanisms related to the “secondary load cycle“ are discussed and compared to the observations made for regular waves.Additionally, attention is paid to experimental determination of hydrodynamic forces. Significant differences between experimentally measured and computed higher harmonic forces are observed and the differences are explained in terms of the eigenmotion of the test setup. Finally, the application of the domain decomposed solver is discussed in an engineering context. Here, a simple and robust way of identifying forces, which may be inaccuvii rately estimated by the Morison equation, is presented. It is suggested that these impacts are recomputed by the domain decomposed solver.

M3 - Ph.D. thesis

BT - Efficient computations of wave loads on offshore structures

PB - Technical University of Denmark

CY - Kgs. Lyngby

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Abdolmaleki, Kourosh. "Modelling of wave impact on offshore structures." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0055.

Tang, Zifan. "One-dimensional mechanistic modelling of gas-liquid two phase flow in pipes." Thesis, Imperial College London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284815.

Hansen, Eirik Schrøder. "Numerical modelling of marine icing on offshore structures and vessels." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18774.

Mondrago, Quevedo Monica. "Probabilistic modelling of geotechnical conditions for offshore wind turbine support structures." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9205.

Rashid, Tariq Mahmood. "Computational modelling of dynamic wind effects relevant to compliant offshore structures." Thesis, University of Hertfordshire, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332219.

Keber, Marko. "Vortex-induced vibration of offshore risers : theoretical modelling and analysis." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=189412.

Turnbull, Michael Stuart. "The numerical modelling of steep waves interacting with structures." Thesis, University of Oxford, 1999. http://ora.ox.ac.uk/objects/uuid:9341dc08-29c1-4752-ad92-ef74d2b5e038.

Foster, Kathryn J. "Design modelling to minimise the risk for offshore platforms." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/7363.

Shi, Qun. "Centrifugal modelling of surface footings subject to combined loadings." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257515.

Phan, Van Trung. "Modelling of the in service behaviour of passive insulated structures for deep sea offshore applications." Thesis, Brest, 2012. http://www.theses.fr/2012BRES0098/document.

Alessi, Lorenzo. "Design of wind tower in existing offshore platforms." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

Ahayan, Sanae. "A constitutive Model for natural Clays : From Laboratory Testing to Modelling of Offshore Monopiles." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0027.

Forbes, Vanessa J. "Structural system reliability framework for fixed offshore platforms." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/844459/.

Rai, Tannaw. "Parametric study of offshore structures with magneto-rheological tuned liquid column damper." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.

Parsa, Arash. "Finite element modelling of stress concentrations in a reinforced concrete offshore structure." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292406.

Nguyen-Sy, Lam. "The theoretical modelling of circular shallow foundation for offshore wind turbines." Thesis, University of Oxford, 2005. http://ora.ox.ac.uk/objects/uuid:fa4000fb-8de6-4093-b528-3e60d774dea0.

Ghalayini, Ramadan. "Structural modelling of the complex Cenozoic zone of the Levant Basin offshore Lebanon." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066316/document.

Heidari, Shayan. "Economic Modelling of Floating Offshore Wind Power : Calculation of Levelized Cost of Energy." Thesis, Mälardalens högskola, Industriell ekonomi och organisation, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-36130.

Yin, Y. "Turbulence model and immersed boundary method development in TELEMAC-3D for offshore structure modelling." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3006448/.

Xu, Xiangtao. "Investigation of the end bearing performance of displacement piles in sand." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0086.

Ravipati, Venkata Raja Sekhar Reddy. "Design and modelling of boat landing for jacket platforms in the Adriatic sea." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

Allsop, Steven Christopher. "Hydrodynamic modelling for structural analysis of tidal stream turbine blades." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/33219.

Le, Yaouanq Sébastien. "Co-simulation redondante d'échelles de modélisation hétérogènes pour une approche phénoménologique." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0032/document.

Sonibare, Wasiu Adedayo. "Structure and evolution of basin and petroleum systems within a transformrelated passive margin setting : data-based insights from crust-scale 3D modelling of the Western Bredasdorp Basin, offshore South Africa." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96832.

Schindler, Peter [Verfasser], Thomas [Gutachter] Jahr, and Gerhard [Gutachter] Jentzsch. "New insights into the structure of the Earth`s crust on- and offshore Northern Victoria Land, Antarctica, by means of gravimetric and magnetic 3D modelling / Peter Schindler ; Gutachter: Thomas Jahr, Gerhard Jentzsch." Jena : Friedrich-Schiller-Universität Jena, 2017. http://d-nb.info/1177594498/34.

Adedipe, Oyewole. "Integrity of offshore structures." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/9692.

Arnal, Vincent. "Modélisation expérimentale d'une éolienne flottante par une approche "sofware-in-the-loop"." Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0037.

Ghadimi, R. "Nonlinear dynamic analysis of offshore structures." Thesis, Cranfield University, 1986. http://hdl.handle.net/1826/3581.

Rodriguez-Sanchez, Jose Efrain. "Fatigue crack repair for offshore structures." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313721.

Trim, A. D. "Probabilistic dynamic analysis of offshore structures." Thesis, Cranfield University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376215.

Klepsvik, Jonny. "Nonlinear wave loads on offshore structures." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36062.

Voldsund, Thor-Arne. "Modelling and Control of Offshore Ploughing Operations." Thesis, Norwegian University of Science and Technology, Department of Engineering Cybernetics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-8816.

Summary: In this thesis work, mathematical models required to simulate an offshore ploughing operation has been derived. This includes a surface vessel model, a model of the plough and its friction force due to seabed sediment and a towline model. A Dynamic Positioning control system has been derived in order to regulate the vessel to a desired location based on the plough’s desired position. A supervisor module has been derived in order to generate the vessel’s reference position in a smooth manner. And finally the total system has been implemented and simulated in the Simulink_TM environment. The surface vessel model derived in this assignment is based on an offshore supply vessel from the ”MatLab Marine GNC Toolbox” in Simulink_TM. The vertical motion of the vessel has been kept constant during simulations, based on the assumption that the buoyancy force of the vessel is large compared to the vertical towline force. The plough’s friction force due to penetration of the seabed sediment has been modeled, based on the content in reference [5], to get a realistic picture of the sediment forces involved in ploughing operations. It was found that the plough’s friction force profile changed with different operational boundaries. The boundaries are the ocean depth and the ploughing speed. For the boundaries in this assignment the resulting ploughing force equation were found to be nonlinear and shaped as a sigmoid function. In this assignment the lumped mass model has been derived for the towline’s motion and proven to give reasonably good numerical results when implemented in the Simulink TM environment. To get a realistic towline motion in seawater, a hydrodynamic quadratic damping force has been added to the equations. This hydrodynamic damping had effect on the towline’s tangential and normal motion components. The DP controller derived in this assignment consists of a PD-controller with feed forward signal from the horizontal towline tension. Feed forward signals are often influenced by noise and must be filtered to obtain low-frequency signals. In this assignment a ordinary 1st-order low-pass filter has been used in order to damp out oscillations from the towline. This filter has been proven to give a good damping effect when the towline was exposed to underwater currents. The DP controller provides good position tracking quality. The supervisor module designed in this assignment consists of a reference generator an a reference model. The supervisor module is responsible for converting input signals for the plough’s desired path into a smooth tracking signal for the vessel’s control system. The reference generator produces smaller intermediate reference signals, as input to the reference model, from a final desired vessel position. A circle of acceptance has been introduced in order to change reference values at a convenient vessel location. This has been proven to give a nice effect on the vessel’s and the plough’s behavior. The reference model has been designed with a speed saturation element, in order to bound the speed of the ploughing operation. During the case simulations it was found that by defining the operation over a longer distance, a more efficient operation is gained. When crossing longer distances the plough will reach the vessel’s speed and underwater current disturbances are small compared to the ploughing force that has gotten time to be built up. Underwater currents has great influence on the towline when the towline’s pulling force is small. In appendix A a CD can be found. On this CD this report can be found, the original work schedule, pictures and the Simulink program for the ploughing operation.

Spraul, Charles. "Suivi en service de la durée de vie des ombilicaux dynamiques pour l’éolien flottant." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0007/document.

Lubbad, Raed Khalil. "Some Aspects of Arctic Offshore Floating Structures." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bygg, anlegg og transport, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12334.

Richardson, Mark Damian. "Dynamically installed anchors for floating offshore structures." University of Western Australia. School of Civil and Resource Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0230.

Foroughi, Abdol Rahim. "Uncertainties in environmental loading on offshore structures." Thesis, University of Sunderland, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385010.

Monahan, Craig C. "Early fatigue crack growth in offshore structures." Thesis, University College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271908.

Kathiroli, S. "Optimisation of members of floating offshore structures." Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235703.

Latini, Corazzini Valentina. "Non-linear dynamic analysis of offshore structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/359/.

Emmerhoff, Ole Johannes. "The slow drift motions of offshore structures." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36503.

Pouliquen, Patricia. "La condition des travailleurs de l’off-shore." Brest, 1993. http://www.theses.fr/1993BRES5001.

Tutar, Mustafa. "Computational modelling of vortex shedding from offshore risers." Thesis, University of Hertfordshire, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268046.

Crawley, Francis Kynoch. "Optimisation and modelling of offshore safety and environment." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288601.

Sadki, Nadia. "Faisabilité de modèles de terrain en offshore." Châtenay-Malabry, Ecole centrale de Paris, 2001. http://www.theses.fr/2001ECAP0711.

Sarkar, Abhijit. "Dynamics of moored offshore structures in random seas." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284464.

Walker, Daniel Anthony Guy. "Interaction of extreme ocean waves with offshore structures." Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:6858dc08-1bd4-4195-8893-1af98d5e68e3.

Aritenang, Wendy. "Behaviour of composite tubular connections in offshore structures." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47336.

Kountouris, Ioannis Savvas. "The assessment of weld defects in offshore structures." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47520.

Liang, Yibo. "Vortex-induced motions of multiple cylindrical offshore structures." Thesis, University of Newcastle upon Tyne, 2018. http://hdl.handle.net/10443/4014.

Souissi, Ridha. "Fléxibilité des jonctions tubulaires dans les structures offshore." Paris 6, 1991. http://www.theses.fr/1991PA066640.