A Comparison Of Alternative Foundation Models For Offshore Wind Turbines And Resulting Long Term Loads

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A Comparison of Alternative Foundation Models for Offshore Wind Turbines and Resulting Long-term Loads

Author : Erica Angelyn Bush
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (444 download)

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Book Synopsis A Comparison of Alternative Foundation Models for Offshore Wind Turbines and Resulting Long-term Loads by : Erica Angelyn Bush

Download or read book A Comparison of Alternative Foundation Models for Offshore Wind Turbines and Resulting Long-term Loads written by Erica Angelyn Bush and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate estimation of structural design loads for wind turbines can help improve cost-effectiveness of wind energy. This study concentrates on predicting long-term characteristic loads for a single design load case for offshore wind turbines associated with an ultimate limit state. Specifically, we study how alternative foundation modeling assumptions and load variability can influence characteristic tower and blade load estimates needed in design. Six foundation models with varying degrees of complexity are compared for a utility-scale 5MW offshore wind turbine. The fixed base model does not account for soil-pile interaction. The apparent fixity model, the modified apparent fixity model, the coupled springs model, and the distributed springs model account for soil-pile interaction by linearizing the lateral stiffness, while the p-y curves model accounts for soil-pile interaction by incorporating the nonlinear response. Accounting for soil-pile flexibility allows the wind turbine model to have similar dynamic characteristics as the true structure. This study shows that accurate structural dynamics is required to produce accurate long-term tower loads, but not necessarily accurate long-term blade loads. All foundation models, including the fixed base model, are shown sufficient for predicting long-term blade load estimates, but flexible foundation models are needed to predict long-term tower loads. We show that linear and nonlinear flexible foundation models are fairly interchangeable for predicting long-term loads for our environmental conditions, wind turbine, and sand profiles because deflections generally stay in the initial quasi-linear range of the p-y curves. In this study, we extrapolate long-term loads using 2D inverse first-order reliability method (FORM) and 3D inverse FORM. The 3D inverse FORM approach accounts for the variability in the load, while the 2D inverse FORM approach does not. We show that characteristic tower and blade loads are strongly influenced by load variability and suggest that it be considered in any effort to predict characteristic long-term loads for design of offshore wind turbines.

Design of Foundations for Offshore Wind Turbines

Author : Subhamoy Bhattacharya
Publisher : John Wiley & Sons
ISBN 13 : 1119128129
Total Pages : 387 pages
Book Rating : 4.1/5 (191 download)

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Book Synopsis Design of Foundations for Offshore Wind Turbines by : Subhamoy Bhattacharya

Download or read book Design of Foundations for Offshore Wind Turbines written by Subhamoy Bhattacharya and published by John Wiley & Sons. This book was released on 2019-04-29 with total page 387 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive reference covering the design of foundations for offshore wind turbines As the demand for “green” energy increases the offshore wind power industry is expanding at a rapid pace around the world. Design of Foundations for Offshore Wind Turbines is a comprehensive reference which covers the design of foundations for offshore wind turbines, and includes examples and case studies. It provides an overview of a wind farm and a wind turbine structure, and examines the different types of loads on the offshore wind turbine structure. Foundation design considerations and the necessary calculations are also covered. The geotechnical site investigation and soil behavior/soil structure interaction are discussed, and the final chapter takes a case study of a wind turbine and demonstrates how to carry out step by step calculations. Key features: New, important subject to the industry. Includes calculations and case studies. Accompanied by a website hosting software and data files. Design of Foundations for Offshore Wind Turbines is a must have reference for engineers within the renewable energy industry and is also a useful guide for graduate students in this area.

Future of wind

Author : International Renewable Energy Agency IRENA
Publisher : International Renewable Energy Agency (IRENA)
ISBN 13 : 9292601970
Total Pages : 161 pages
Book Rating : 4.2/5 (926 download)

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Book Synopsis Future of wind by : International Renewable Energy Agency IRENA

Download or read book Future of wind written by International Renewable Energy Agency IRENA and published by International Renewable Energy Agency (IRENA). This book was released on 2019-10-01 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study presents options to speed up the deployment of wind power, both onshore and offshore, until 2050. It builds on IRENA’s global roadmap to scale up renewables and meet climate goals.

Stabilisation Behaviour of Cyclically Loaded Shallow Foundations for Offshore Wind Turbines

Author : Hendrik Sturm
Publisher : KIT Scientific Publishing
ISBN 13 : 3866444133
Total Pages : 154 pages
Book Rating : 4.8/5 (664 download)

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Book Synopsis Stabilisation Behaviour of Cyclically Loaded Shallow Foundations for Offshore Wind Turbines by : Hendrik Sturm

Download or read book Stabilisation Behaviour of Cyclically Loaded Shallow Foundations for Offshore Wind Turbines written by Hendrik Sturm and published by KIT Scientific Publishing. This book was released on 2014-10-16 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This work presents the results of model tests and numerical simulations of shallow foundations subjected to cyclic loads typical of offshore loadings. Small-scale model tests on a shallow foundation, subjected alternately to cyclic loads with large and small amplitudes, have shown that the accumulated rotations due to large amplitude loads reduce during later phases with smaller amplitudes. Numerical simulations have revealed that this behaviour of cyclically loaded shallow foundations is quantitatively influenced by the load amplitude and direction, and number of load cycles. This work concludes with a proposal for foundation geometries that efficiently resist offshore cyclic loads."--Page 4 of cover.

Soil-Structure Modeling and Design Considerations for Offshore Wind Turbine Monopile Foundations

Author : Wystan Carswell
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (944 download)

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Book Synopsis Soil-Structure Modeling and Design Considerations for Offshore Wind Turbine Monopile Foundations by : Wystan Carswell

Download or read book Soil-Structure Modeling and Design Considerations for Offshore Wind Turbine Monopile Foundations written by Wystan Carswell and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Offshore wind turbine (OWT) support structures account for 20-25% of the capital cost for offshore wind installations, making it essential to optimize the design of the tower, substructure, and foundation to the extent possible. This dissertation focuses on monopile foundations, as the vast majority (approximately 75%) of currently installed OWTs are supported by monopile structures. The objective of this dissertation is to provide information on the behavior of monopile support structures to better substantiate design and planning decisions and to provide a basis for reducing the structural material costs. In pursuit of these objectives, research is presented on the topics of hysteretic soil-structure damping (referred to as foundation damping), cyclic degradation of soil properties, and the impact of marine growth on OWT monopile support structures. OWTs are lightly damped structures that must withstand highly uncertain offshore wind and wave loads. In addition to stochastic load amplitudes, the dynamic behavior of OWTs must be designed with consideration of stochastic load frequency from waves and mechanical load frequencies associated with the spinning rotor during power production. The close proximity of the OWT natural frequency to excitation frequencies combined with light damping necessitates a thorough analysis of various sources of damping within the OWT system; of these sources of damping, least is known about the contributions of damping from soil-structure interaction (foundation damping), though researchers have back-calculated foundation damping from "rotor-stop" tests after estimating aerodynamic, hydrodynamic, and structural damping with numerical models. Because design guidelines do not currently recommend methods for determining foundation damping, it is typically neglected. The significance of foundation damping on monopile-supported OWTs subjected to extreme storm loading was investigated using a linear elastic two-dimensional finite element model. A simplified foundation model based on the soil-pile mudline stiffness matrix was used to represent the monopile, and hysteretic energy loss in the foundation was converted into a viscous, rotational dashpot at the mudline to represent foundation damping. The percent critical damping contributed to the OWT structural system by foundation damping was quantified using the logarithmic decrement method on a finite element free vibration time history, and stochastic time history analysis of extreme storm conditions indicated that mudline OWT foundation damping can significantly decrease the maximum and standard deviation of mudline moment. Further investigation of foundation damping on cyclic load demand for monopile-supported OWTs was performed considering the design situations of power production, emergency shutdown, and parked conditions. The NREL 5MW Reference Turbine was modeled using the aero-hydro-elastic software FAST and included linear mudline stiffness and damping matrices to take into account soil-structure interaction. Foundation damping was modeled using viscous rotational mudline dashpots which were calculated as a function of hysteretic energy loss, cyclic mudline rotation amplitude, and OWT natural frequency. Lateral monopile capacity can be significantly affected by cyclic loading, causing failure at cyclic load amplitudes lower than the failure load under monotonic loading. For monopiles in clay, undrained clay behavior under short-term cyclic soil-pile loading (e.g. extreme storm conditions) typically includes plastic soil deformation resulting from reductions in soil modulus and undrained shear strength which occur as a function of pore pressure build-up. These impacts affect the assessment of the ultimate and serviceability limit states of OWTs via natural frequency degradation and accumulated permanent rotation at the mudline, respectively. Novel combinations of existing p-y curve design methods were used to compare the impact of short-term cyclic loading on monopiles in soft, medium, and stiff clay. Marine growth increases mass and surface roughness for offshore structures, which can reduce natural frequency and increase hydrodynamic loads, and can also interfere with corrosion protection and fatigue inspections. Design standards and guidelines do not have a unified long-term approach for marine growth on OWTs, though taking into account added mass and increased drag is recommended. Some standards recommend inspection and cleaning of marine growth, but this would negate the artificial reef benefits which have been touted as a potential boon to the local marine habitat. The effects of marine growth on monopile-supported OWTs in terms of natural frequency and hydrodynamic loading are examined, and preliminary recommendations are given from the engineering perspective on the role of marine growth in OWT support structure design.

The Economics of Wind Energy

Author :
Publisher : EWEA
ISBN 13 :
Total Pages : 156 pages
Book Rating : 4./5 ( download)

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Book Synopsis The Economics of Wind Energy by :

Download or read book The Economics of Wind Energy written by and published by EWEA. This book was released on 2009 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Cyclic and Static Laboratory Tests on Drammen Clay

Author :
Publisher :
ISBN 13 : 9788254600696
Total Pages : 50 pages
Book Rating : 4.6/5 (6 download)

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Book Synopsis Cyclic and Static Laboratory Tests on Drammen Clay by :

Download or read book Cyclic and Static Laboratory Tests on Drammen Clay written by and published by . This book was released on 1980 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Wind Energy Engineering

Author : Trevor Letcher
Publisher : Elsevier
ISBN 13 : 0323958303
Total Pages : 588 pages
Book Rating : 4.3/5 (239 download)

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Book Synopsis Wind Energy Engineering by : Trevor Letcher

Download or read book Wind Energy Engineering written by Trevor Letcher and published by Elsevier. This book was released on 2023-05-08 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind Energy Engineering: A Handbook for Onshore and Offshore Wind Turbines, Second Edition continues to be the most advanced, up-to-date and research-focused text on all aspects of wind energy engineering. Covering a wider spectrum of topics in the field of wind turbines (offshore and onshore), this new edition includes new intelligent turbine designs and optimization, current challenges and efficiencies, remote sensing and smart monitoring, and key areas of advancement, such as floating wind turbines. Each chapter includes a research overview with a detailed analysis and new case studies looking at how recent research developments can be applied. Written by some of the most forward-thinking professionals in the field, and giving a complete examination of one of the most promising and efficient sources of renewable energy, this book is an invaluable reference into this cross-disciplinary field for engineers. Offers an all-around understanding of the links between worldwide resources, including wind turbine technology, electricity and environmental issues, and economics Provide the very latest research and development in over 33 fields of endeavor related to wind power Includes extensive sets of references in each chapter, giving readers all the very latest thinking and information on each topic

Floating Offshore Wind Energy

Author : Joao Cruz
Publisher : Springer
ISBN 13 : 3319293982
Total Pages : 345 pages
Book Rating : 4.3/5 (192 download)

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Book Synopsis Floating Offshore Wind Energy by : Joao Cruz

Download or read book Floating Offshore Wind Energy written by Joao Cruz and published by Springer. This book was released on 2016-08-20 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a state-of-the-art review of floating offshore wind turbines (FOWT). It offers developers a global perspective on floating offshore wind energy conversion technology, documenting the key challenges and practical solutions that this new industry has found to date. Drawing on a wide network of experts, it reviews the conception, early design stages, load & structural analysis and the construction of FOWT. It also presents and discusses data from pioneering projects. Written by experienced professionals from a mix of academia and industry, the content is both practical and visionary. As one of the first titles dedicated to FOWT, it is a must-have for anyone interested in offshore renewable energy conversion technologies.

Dynamics of Fixed Marine Structures

Author : N. D. P. Barltrop
Publisher : Butterworth-Heinemann
ISBN 13 : 1483162559
Total Pages : 785 pages
Book Rating : 4.4/5 (831 download)

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Book Synopsis Dynamics of Fixed Marine Structures by : N. D. P. Barltrop

Download or read book Dynamics of Fixed Marine Structures written by N. D. P. Barltrop and published by Butterworth-Heinemann. This book was released on 2013-10-22 with total page 785 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dynamics of Fixed Marine Structures, Third Edition proves guidance on the dynamic design of fixed structures subject to wave and current action. The text is an update of the ""UR8"" design guide ""Dynamics of Marine Structures"" with discussion of foundations, wind turbulence, offshore installations, earthquakes, and strength and fatigue. The book employs analytical methods of static and dynamic structural analysis techniques, particularly the statistical and spectral methods when applied to loading and in the calculating dynamic responses. The statistical methods are explained when used to wave, wind, and earthquake calculations, together with the problems encountered in actual applications. Of importance to fixed offshore platforms are the soil properties and foundation covering soil behavior, site investigation, testing, seabed stability, gravity structures, and the use of single piles. Methods of forecasting, measuring, and modeling of waves and currents are also presented in offshore structure construction. Basic hydrodynamics is explained in understanding wave theory, and some description is given to forecasting of environmental conditions that will affect the structures. The effects of vortex-induced vibrations on the structure are explained, and the three methods that can prevent vortex-induced oscillations are given. Wind turbulence or wind loads are analyzed against short natural period or long natural periods of structures. The transportation of offshore platforms, installation, and pile driving, including examples of the applications found in the book, are given as well. The guide is helpful for offshore engineers, designers of inshore jetties, clients needing design and analysis work, specialists related to offshore structural engineering, and students in offshore engineering.

Performance and Bearing Behavior of Foundations for Offshore Wind Turbines

Author : Xu Yang
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (19 download)

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Book Synopsis Performance and Bearing Behavior of Foundations for Offshore Wind Turbines by : Xu Yang

Download or read book Performance and Bearing Behavior of Foundations for Offshore Wind Turbines written by Xu Yang and published by . This book was released on 2018 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Offshore wind energy is one of the primary renewable sources of energy. The ongoing development of the capacity and distance to shore of offshore wind turbines (OWTs) lead to more severe loading conditions. The substructures for OWTs are required to be capable of withstanding the combined loads with vertical loads from the weight of upper structures, and relatively high lateral loads and resultant moments induced by waves, winds, ice and currents. Two types of innovative foundations: the suction bucket foundation and monopile-friction wheel foundation are investigated in this dissertation via centrifuge modellings and finite element (FE) analyses.Suction bucket foundations are a promising foundation option for offshore wind turbines. To assess the lateral-moment loading capacity of bucket foundations, a group of 3-D finite element (FE) simulations with different bucket dimensions in sand and clay is carried out based on the centrifuge model tests. The numerical methods are validated by comparisons with the results of centrifuge tests, and assessed by sensitivity analyses regarding the influences of soil properties and soil-foundation interface parameters. The interaction between the bucket and surrounding soil is illustrated in order to demonstrate the bearing behavior and failure mechanism of the bucket foundation. It is shown that in the ultimate state, the maximum passive earth pressure acting on the external skirt in the loading direction is approximately 4 times larger than that on the internal skirt. Furthermore, parametric studies on the L/D ratios (L is the skirt length and D is the bucket diameter) and loading eccentricity are conducted and discussed. Consequently, a modified calculation method is proposed to predict the ultimate lateral-moment loading capacity of bucket foundations in sand. The method is validated by field and laboratory test data.The monopile-friction wheel foundation integrates a wheel to a monopile to improve the lateral performance. Two types of wheels, the solid wheel and gravel wheel, are discussed in this part. A series of tests on the monopile, hybrid foundations with solid wheels of different diameters and thicknesses, and single solid wheel foundation were conducted. The results show that the lateral bearing capacity and stiffness increase significantly by adding a solid wheel to the monopile, and the improvement is related to the diameter and thickness of the wheel. An extensive experimental research regarding to the influential factors such as the embedment of the wheel and the vertical load is also presented. By means of FEM, the load transfer mechanism, interaction between the foundation and soil, and the bending moment in the pile are illustrated to study how the solid wheel contributes to the performance of the foundation system. Moreover, the effects of load eccentricity and vertical load are investigated by FEM analyses.The gravel wheel is a ring frame filled with large particles to potentially utilize the gravel or crushed stones in offshore areas. The results of centrifuge tests and FEM analyses demonstrate that the lateral loading capacity of the monopile increases when combined with a gravel wheel, and the improvement depends on the diameter and thickness of the wheel. By means of FEM, the interaction between the pile and surrounding soils and gravel fill are illustrated to interpret the effect of the gravel wheel on the hybrid system. Furthermore, an equivalent layer method adopting the conventional p-y curves is suggested to predict the lateral response of the hybrid foundation. This method is validated by comparisons with the centrifuge tests results. Finally, a case study of the monopile-gravel wheel foundation indicates that the gravel wheel is less efficient in configurations where the ultimate capacity of the hybrid system is dictated by the bending capacity of structures rather than the strengths of soils.

Wind Energy Explained

Author : James F. Manwell
Publisher : John Wiley & Sons
ISBN 13 : 9780470686287
Total Pages : 704 pages
Book Rating : 4.6/5 (862 download)

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Book Synopsis Wind Energy Explained by : James F. Manwell

Download or read book Wind Energy Explained written by James F. Manwell and published by John Wiley & Sons. This book was released on 2010-09-14 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind energy’s bestselling textbook- fully revised. This must-have second edition includes up-to-date data, diagrams, illustrations and thorough new material on: the fundamentals of wind turbine aerodynamics; wind turbine testing and modelling; wind turbine design standards; offshore wind energy; special purpose applications, such as energy storage and fuel production. Fifty additional homework problems and a new appendix on data processing make this comprehensive edition perfect for engineering students. This book offers a complete examination of one of the most promising sources of renewable energy and is a great introduction to this cross-disciplinary field for practising engineers. “provides a wealth of information and is an excellent reference book for people interested in the subject of wind energy.” (IEEE Power & Energy Magazine, November/December 2003) “deserves a place in the library of every university and college where renewable energy is taught.” (The International Journal of Electrical Engineering Education, Vol.41, No.2 April 2004) “a very comprehensive and well-organized treatment of the current status of wind power.” (Choice, Vol. 40, No. 4, December 2002)

Trends in Renewable Energies Offshore

Author : C. Guedes Soares
Publisher : CRC Press
ISBN 13 : 1000837319
Total Pages : 969 pages
Book Rating : 4.0/5 (8 download)

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Book Synopsis Trends in Renewable Energies Offshore by : C. Guedes Soares

Download or read book Trends in Renewable Energies Offshore written by C. Guedes Soares and published by CRC Press. This book was released on 2022-10-26 with total page 969 pages. Available in PDF, EPUB and Kindle. Book excerpt: Renewable energy resources offshore are a growing contributor to the total energy production in a growing number of countries. As a result the interest in the topic is increasing. Trends in Renewable Energies Offshore includes the papers presented at the 5th International Conference on Renewable Energies Offshore (RENEW 2022, Lisbon, Portugal, 8-10 November 2022), and covers recent developments and experiences gained in concept development, design and operation of such devices. The scope of the contributions is broad, covering all aspects of renewable energies offshore activities, including: • Resource assessment • Tidal Energy • Wave Energy • Wind Energy • Solar Energy • Renewable Energy Devices • Multiuse Platforms • Maintenance planning • Materials and structural design Trends in Renewable Energies Offshore will be of interest to academics and professionals involved or interested in applications of renewable energy resources offshore. The ‘Proceedings in Marine Technology and Ocean Engineering’ series is dedicated to the publication of proceedings of peer-reviewed international conferences dealing with various aspects of ‘Marine Technology and Ocean Engineering’. The Series includes the proceedings of the following conferences: the International Maritime Association of the Mediterranean (IMAM) conferences, the Marine Structures (MARSTRUCT) conferences, the Renewable Energies Offshore (RENEW) conferences and the Maritime Technology (MARTECH) conferences. The ‘Marine Technology and Ocean Engineering’ series is also open to new conferences that cover topics on the sustainable exploration and exploitation of marine resources in various fields, such as maritime transport and ports, usage of the ocean including coastal areas, nautical activities, the exploration and exploitation of mineral resources, the protection of the marine environment and its resources, and risk analysis, safety and reliability. The aim of the series is to stimulate advanced education and training through the wide dissemination of the results of scientific research.

Governance and Sustainability of Responsible Research and Innovation Processes

Author : Fernando Ferri
Publisher : Springer
ISBN 13 : 331973105X
Total Pages : 112 pages
Book Rating : 4.3/5 (197 download)

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Book Synopsis Governance and Sustainability of Responsible Research and Innovation Processes by : Fernando Ferri

Download or read book Governance and Sustainability of Responsible Research and Innovation Processes written by Fernando Ferri and published by Springer. This book was released on 2018-01-24 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides methods and practical cases and experiences with the aim of stimulating Responsible Research and Innovation (RRI) through the direct engagement of researchers, Civil Society Organisations (CSOs), citizens, industry stakeholders, policy and decision makers, research funders and communicators. The book furthermore aims to advance debate on Responsible Research and Innovation and also to reinforce the RRI community identity. With chapters covering governance, public engagement and inclusion in responsible R&D and innovation processes; RRI actions in science education and communication; gender and ethical issues in RRI initiatives; and sustainability of RRI processes, the book is solidly part of the Europe 2020 strategy to promote a vision for a stronger collaborations between social, natural and physical scientists and the societal actors for a wider dimensions of science and innovation and the role in environmental preservation. Chapters 1 and 3 are open access under a CC BY 4.0 license via link.springer.com.

Proceedings of the 1st Vietnam Symposium on Advances in Offshore Engineering

Author : M.F. Randolph
Publisher : Springer
ISBN 13 : 9811323062
Total Pages : 616 pages
Book Rating : 4.8/5 (113 download)

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Book Synopsis Proceedings of the 1st Vietnam Symposium on Advances in Offshore Engineering by : M.F. Randolph

Download or read book Proceedings of the 1st Vietnam Symposium on Advances in Offshore Engineering written by M.F. Randolph and published by Springer. This book was released on 2018-09-24 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: These proceedings gather a selection of refereed papers presented at the 1st Vietnam Symposium on Advances in Offshore Engineering (VSOE 2018), held on 1–3 November 2018 in Hanoi, Vietnam. The contributions from researchers, practitioners, policymakers, and entrepreneurs address technological and policy changes intended to promote renewable energies, and to generate business opportunities in oil and gas and offshore renewable energy. With a special focus on energy and geotechnics, the book brings together the latest lessons learned in offshore engineering, technological innovations, cost-effective and safer foundations and structural solutions, environmental protection, hazards, vulnerability, and risk management. The book offers a valuable resource for all graduate students, researchers and industrial practitioners working in the fields of offshore engineering and renewable energies.

Foundations for an Offshore Wind Turbine

Author : Duncan Rath Kopp
Publisher :
ISBN 13 :
Total Pages : 123 pages
Book Rating : 4.:/5 (693 download)

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Book Synopsis Foundations for an Offshore Wind Turbine by : Duncan Rath Kopp

Download or read book Foundations for an Offshore Wind Turbine written by Duncan Rath Kopp and published by . This book was released on 2010 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: Worldwide energy demand is growing rapidly, and there is great interest in reducing the current reliance on fossil fuels for uses such as power generation, transportation, and manufacturing. Renewable energy sources, such as solar and wind, are abundant but have very low power densities. The US is in the process of approving its first offshore wind farm, located in Nantucket Sound. Geotechnical factors will play a large role in the development of offshore wind projects due to the high cost contribution from foundations, and the high loads associated with storm conditions. Offshore wind turbine foundations provide unique design challenges. First, various foundation alternatives exist, so it is important that an appropriate cost-effective foundation type be selected. Second, the loads and soil conditions will vary for each location. Therefore, it is important to ensure the foundation can adequately support vertical and horizontal loads. Finally, each turbine manufacturer has unique deflection and rotation criteria. Therefore, the foundation should perform within those tolerances, even under worst-case loading. This thesis considers the performance of a monopile foundation under typical vertical and horizontal storm loading conditions. Capacity, deflection, and rotation of a proposed monopile foundation are calculated by various methods to simulate the design procedure. The results show that very stiff foundations are required to keep pile head movements within design tolerances.

Experimental and Numerical Modeling of the Response of Foundations to Cyclic Loading for Offshore Structures

Author : Bao Li Zheng
Publisher :
ISBN 13 : 9780438930551
Total Pages : pages
Book Rating : 4.9/5 (35 download)

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Book Synopsis Experimental and Numerical Modeling of the Response of Foundations to Cyclic Loading for Offshore Structures by : Bao Li Zheng

Download or read book Experimental and Numerical Modeling of the Response of Foundations to Cyclic Loading for Offshore Structures written by Bao Li Zheng and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Design of offshore foundations can be difficult due to challenging soils that can vary from high plasticity, soft clay to very dense sand, and complex loading conditions from the respective environments (e.g., wind, waves, seismicity), in the form of combinations of monotonic and cyclic load patterns. Understanding the interaction of the soil-foundation-structure system under design loads is critical for reliable operations of offshore structures. This dissertation provides the evaluation of performance and investigation of mechanisms against cyclic loading for: (1) subsea wellhead-pipeline-manifold systems on soft clay; and (2) multi-pile-supported offshore wind turbine structures in dense sand. Commonly, the product from deep gas wells is collected at a central manifold founded on the seabed via jumpers (i.e., pipelines). The connections to the jumpers are relatively stiff, with limited tolerance against shear failure induced from relative displacement. A centrifuge test was conducted on the 9-m centrifuge at the UC Davis Center for Geotechnical Modeling to study the seismic performance of a caisson-supported manifold structure and a deeply-installed wellhead founded on soft clay when subjected to extreme and abnormal level earthquakes. Dynamic response of jumpers connecting the manifold structure and the wellhead was interpreted as the difference between the dynamic displacement time histories between the manifold structure, the wellhead, and the free-field clay surface. Comparison demonstrated that the governing jumper connections lie between the manifold and the wellhead and between the wellhead and the free-field surface, and the wellhead is the more critical component under the specific ground motion. Offshore wind turbine structures (OWTS) are subject to wind and wave loads with varying magnitudes of static and cyclic loads over their design lives. During normal operation, these structures are further loaded by rotor and blade-passing imbalance forces. Cyclic loading can cause significant degradation in the capacity and generate excessive movement, as well as reduction of the soil-pile stiffness and the natural frequency toward resonance with rotor frequencies. A centrifuge program was designed and performed on the 1-m Schaevitz centrifuge at UC Davis to evaluate the performance of tension piles against cyclic loads for multi-pile-supported offshore wind turbines. The potential for obtaining meaningful results using a small centrifuge for this application was demonstrated, and an initial data set from centrifuge testing of piles subjected to one-way and two-way cyclic axial loading was developed. The data set was presented and evaluated within the interaction diagram framework that is commonly used to predict the cyclic stability of piles. Results from the centrifuge tests were generally consistent with predictions from interaction diagrams (e.g., under one-way loading, increase in cyclic load amplitude lowers pile stability). However, inconsistencies were also observed in the comparison, such as a reduction of capacity for combinations of static and cyclic loads where the interaction diagram suggested “stable” behavior, and an increase in capacity for combinations where the diagram suggested “unstable” behavior. Other observations and implications of the centrifuge results are discussed. Inconsistencies between expected and observed response, such as that mentioned above, demonstrated a lack of full understanding on the complex mechanisms concerning the cyclic stability of tension piles. An axisymmetric finite-element model was developed in OpenSees (McKenna et al., 2010) to help understand the mechanisms affecting the evolution of the axial response (i.e., capacity, stiffness, and pullout rate) under different load combinations of static and cyclic loads on tension piles. The 2004 Dafalias and Manzari bounding surface plasticity model was used for the response of the soil. Five loading stages were performed to simulate this axial problem: confinement, installation by cylindrical cavity expansion and downward shear, static tensile shearing, cyclic shearing, and monotonic pullout. Results from the numerical analysis demonstrated the dependence of the evolution of axial response on the magnitudes of the static and cyclic shear stresses, and the number of applied cycles. Specifically, the analysis suggested the possibility for increase in tensile capacity and stiffening of the soil-pile stiffness for some load combinations, which is typically not considered in design. Other mechanisms and observations, as well as practical implication on current design, are presented.