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G T Houlsby - One of the best experts on this subject based on the ideXlab platform.
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pisa design model for monopiles for Offshore Wind Turbines application to a stiff glacial clay till
Geotechnique, 2019Co-Authors: B W Byrne, G T Houlsby, C M Martin, H J Burd, Kenneth Gavin, David Igoe, R J Jardine, Ross A Mcadam, David M Potts, David M G TabordaAbstract:Offshore Wind Turbines in shallow coastal waters are typically supported on monopile foundations. Although three-dimensional (3D) finite-element methods are available for the design of monopiles in...
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helical piles an innovative foundation design option for Offshore Wind Turbines
Philosophical Transactions of the Royal Society A, 2015Co-Authors: B W Byrne, G T HoulsbyAbstract:Offshore Wind Turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certa...
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helical piles an innovative foundation design option for Offshore Wind Turbines
Philosophical Transactions of the Royal Society A, 2015Co-Authors: B W Byrne, G T HoulsbyAbstract:Offshore Wind Turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certainly in UK waters, have taken place in relatively shallow water and close to shore. This limits the scale of the engineering to relatively simple structures, such as those using monopile foundations, and these have been the most common design to date, in UK waters. However, as larger Turbines are designed, or they are placed in deeper water, it will be necessary to use multi-footing structures such as tripods or jackets. For these designs, the tension on the upWind footing becomes the critical design condition. Driven pile foundations could be used, as could suction-installed foundations. However, in this paper, we present another concept-the use of helical pile foundations. These foundations are routinely applied onshore where large tension capacities are required. However, for use Offshore, a significant upscaling of the technology will be needed, particularly of the equipment required for installation of the piles. A clear understanding of the relevant geotechnical engineering will be needed if this upscaling is to be successful.
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suction caisson foundations for Offshore Wind Turbines
Wind Engineering, 2002Co-Authors: B W Byrne, G T Houlsby, C M Martin, Peter FishAbstract:This paper outlines a �1.5m,three year,research project that commenced during the middle of 2002 to determine a design framework for shallow foundations for Offshore Wind Turbines.The shallow foundations in focus are suction-installed skirted foundations otherwise known as suction caissons (Houlsby and Byrne, 2000). There are eight distinct themes to the research covering all aspectsof the geotechnical performance of these foundations.The funding for the project has been obtained from the Department of Trade and Industry (�917k), Industrial Partners (� 373k) and the Engineering and Physical Sciences Research Council (�221k). The results will feed into the design process for Offshore Wind Turbines almostimmediately.
Ana M Page - One of the best experts on this subject based on the ideXlab platform.
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a new foundation model for integrated analyses of monopile based Offshore Wind Turbines
Energy Procedia, 2017Co-Authors: Kristoffer Skjolden Skau, Ana M Page, Hans Pette Jostad, Gudmund Reidar EiksundAbstract:Abstract Offshore Wind Turbines are highly dynamic and tightly coupled systems subjected to variable cyclic loads. Designing and optimizing the support structure is a complex task, where several load scenarios have to be analysed to account for the various uncertainties. Improving the accuracy of analysis tools used in the design and optimization process can increase the reliability and thus reduce uncertainties and risks. For monopiles supporting Offshore Wind Turbines, the current design practice is to model the foundation response by API p-y curves. Discrepancies between the assumptions considered in the API p-y curves and the actual pile behaviour have been extensively identified in the literature, and their applicability to predict pile behaviour in integrated analyses of Offshore Wind Turbines has been questioned. This paper presents a new foundation model for integrated analyses of monopile-based Offshore Wind Turbines. The model is simple and hence computational efficient, but still able to reproduce key characteristic in monopile foundation behaviour that are not accounted for in the current modelling approach. The model input is based on finite element analyses of the soil and the foundation, which makes it possible to calibrate the model to different soil conditions. The basic features of the model are described and its limitations are discussed. The performance of the new foundation model is demonstrated for time histories that are representative for an Offshore Wind turbine and compared with the response from API p-y curves. In contrast to the API p-y curves, the new model can reproduce different foundation stiffness for unloading and reloading and foundation damping depending on the loading history, which is observed in real pile behaviour. A more realistic foundation modelling will lead to more accurate predicted loads, reduced uncertainties in the estimated fatigue lifetime and therefore reduced risk in the design.
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influence of soil parameters on the fatigue lifetime of Offshore Wind Turbines with monopile support structure
Energy Procedia, 2016Co-Authors: Sebastian Schafhirt, Gudmund Reidar Eiksund, Ana M Page, Michael MuskulusAbstract:Abstract Designing support structures for Offshore Wind Turbines is a complex task as these are highly dynamic systems subjected to long-term cyclic loads with variable amplitude. Long-term cyclic loading may cause stiffening or softening of the soil around the pile foundation of an Offshore Wind turbine, which leads to variations in the foundation stiffness and accumulated permanent rotation of the pile. Although variations in the foundation stiffness can negatively impact the fatigue life, the long-term variability of the soil conditions is normally not considered in the fatigue damage assessment. The main objective of this study is the investigation of the impact of changes in soil parameters on the fatigue lifetime for an Offshore Wind turbine founded in loose sand. For this purpose, a generic monopile based Offshore Wind turbine with flexible foundation model was used. The soil-pile interaction was modeled with a distributed spring model using nonlinear API p-y curves. Integrated analyses in the time domain were performed and fatigue damage was assessed in terms of a damage equivalent bending moment at mudline. The fatigue lifetime varies between -9 percent and +4 percent when considering changes in soil conditions, depending on the assumption of soil softening or stiffening, respectively. These results indicate that changes in soil parameters should be taken into account in the fatigue damage calculations of Offshore Wind Turbines for more precise fatigue lifetime estimation. Moreover, it is emphasized that more accurate modeling of soil-pile interaction is required in the design and optimization of Offshore Wind Turbines.
Michael Muskulus - One of the best experts on this subject based on the ideXlab platform.
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influence of soil parameters on the fatigue lifetime of Offshore Wind Turbines with monopile support structure
Energy Procedia, 2016Co-Authors: Sebastian Schafhirt, Gudmund Reidar Eiksund, Ana M Page, Michael MuskulusAbstract:Abstract Designing support structures for Offshore Wind Turbines is a complex task as these are highly dynamic systems subjected to long-term cyclic loads with variable amplitude. Long-term cyclic loading may cause stiffening or softening of the soil around the pile foundation of an Offshore Wind turbine, which leads to variations in the foundation stiffness and accumulated permanent rotation of the pile. Although variations in the foundation stiffness can negatively impact the fatigue life, the long-term variability of the soil conditions is normally not considered in the fatigue damage assessment. The main objective of this study is the investigation of the impact of changes in soil parameters on the fatigue lifetime for an Offshore Wind turbine founded in loose sand. For this purpose, a generic monopile based Offshore Wind turbine with flexible foundation model was used. The soil-pile interaction was modeled with a distributed spring model using nonlinear API p-y curves. Integrated analyses in the time domain were performed and fatigue damage was assessed in terms of a damage equivalent bending moment at mudline. The fatigue lifetime varies between -9 percent and +4 percent when considering changes in soil conditions, depending on the assumption of soil softening or stiffening, respectively. These results indicate that changes in soil parameters should be taken into account in the fatigue damage calculations of Offshore Wind Turbines for more precise fatigue lifetime estimation. Moreover, it is emphasized that more accurate modeling of soil-pile interaction is required in the design and optimization of Offshore Wind Turbines.
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effect of load sequence and weather seasonality on fatigue crack growth for monopile based Offshore Wind Turbines
Energy Procedia, 2016Co-Authors: Lisa Sabine Ziegler, Sebastian Schafhirt, Matti Niclas Scheu, Michael MuskulusAbstract:Abstract Offshore Wind Turbines are subjected to variable amplitude loading, but the impact of load sequence is commonly neglected in fatigue analysis. This paper presents an initial investigation if load sequence and weather seasonality influence fatigue crack growth for monopile-based Offshore Wind Turbines. Focus is on the load sequence effect introduced by the non-linearity of crack propagation. Fatigue crack growth at two structural hot spots was analyzed with a fracture mechanics model applying Paris’ law. The model was calibrated to yield an identical lifetime as a SN-curve analysis. Input into the fracture mechanics model are structural stresses due to environmental and operational loading. Weather seasonality was simulated with a Markov model. Results show that loading sequence has only a negligible effect on crack sizes under the assumption made in this study. This makes fatigue lifetime predictions independent of weather seasonality. However, it becomes relevant for the prediction of future propagation of detected fatigue cracks throughout the year.
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reanalysis of jacket support structure for computer aided optimization of Offshore Wind Turbines with a genetic algorithm
The Twenty-fourth International Ocean and Polar Engineering Conference, 2014Co-Authors: Sebastian Schafhirt, Daniel Zwick, Michael MuskulusAbstract:The optimization of jacket support structures for Offshore Wind Turbines is a nontrivial task. Due to nonlinear and time history-dependent effects, the analysis is simulation-based. Structural optimization using time-domain simulations is computationally demanding and difficult and typically requires a gradient-free approach. A genetic algorithm can be used for this purpose, but is limited by the computational resources available. This paper presents an approach to modifying the standard genetic algorithm for the automatic optimization of Offshore Wind Turbines with jacket support structures under fatigue constraints. It is shown that performing a reanalysis of the jacket structures, by using performance data from earlier analyses in parallel with the simulation-based analysis process, requires a smaller number of iterations to obtain improved designs. Thus, the use of reanalysis within the genetic algorithm speeds up the algorithm significantly.
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iterative optimization approach for the design of full height lattice towers for Offshore Wind Turbines
Energy Procedia, 2012Co-Authors: Daniel Zwick, Michael Muskulus, Geir MoeAbstract:Abstract Among several possible support structure types for Offshore Wind Turbines, a full-height lattice tower is one design option. Advantages of this design are the smaller amount of steel used for the structure compared to other concepts, and the possibility to install the whole structure in one operation. Based on the complexity of dynamic loadings on the support structure by Wind and wave as well as operational loads, an initial lattice tower design with constant member dimensions over the tower height shows a large optimization potential and can be optimized section by section. This paper presents basic considerations for an iterative optimization approach and identifies sensitivities for the optimization process of a full-height lattice tower. It was found that an analysis with constant member dimensions over the tower height gives an indication about the required dimensions for an optimized design.
B W Byrne - One of the best experts on this subject based on the ideXlab platform.
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pisa design model for monopiles for Offshore Wind Turbines application to a stiff glacial clay till
Geotechnique, 2019Co-Authors: B W Byrne, G T Houlsby, C M Martin, H J Burd, Kenneth Gavin, David Igoe, R J Jardine, Ross A Mcadam, David M Potts, David M G TabordaAbstract:Offshore Wind Turbines in shallow coastal waters are typically supported on monopile foundations. Although three-dimensional (3D) finite-element methods are available for the design of monopiles in...
-
helical piles an innovative foundation design option for Offshore Wind Turbines
Philosophical Transactions of the Royal Society A, 2015Co-Authors: B W Byrne, G T HoulsbyAbstract:Offshore Wind Turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certa...
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helical piles an innovative foundation design option for Offshore Wind Turbines
Philosophical Transactions of the Royal Society A, 2015Co-Authors: B W Byrne, G T HoulsbyAbstract:Offshore Wind Turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certainly in UK waters, have taken place in relatively shallow water and close to shore. This limits the scale of the engineering to relatively simple structures, such as those using monopile foundations, and these have been the most common design to date, in UK waters. However, as larger Turbines are designed, or they are placed in deeper water, it will be necessary to use multi-footing structures such as tripods or jackets. For these designs, the tension on the upWind footing becomes the critical design condition. Driven pile foundations could be used, as could suction-installed foundations. However, in this paper, we present another concept-the use of helical pile foundations. These foundations are routinely applied onshore where large tension capacities are required. However, for use Offshore, a significant upscaling of the technology will be needed, particularly of the equipment required for installation of the piles. A clear understanding of the relevant geotechnical engineering will be needed if this upscaling is to be successful.
-
suction caisson foundations for Offshore Wind Turbines
Wind Engineering, 2002Co-Authors: B W Byrne, G T Houlsby, C M Martin, Peter FishAbstract:This paper outlines a �1.5m,three year,research project that commenced during the middle of 2002 to determine a design framework for shallow foundations for Offshore Wind Turbines.The shallow foundations in focus are suction-installed skirted foundations otherwise known as suction caissons (Houlsby and Byrne, 2000). There are eight distinct themes to the research covering all aspectsof the geotechnical performance of these foundations.The funding for the project has been obtained from the Department of Trade and Industry (�917k), Industrial Partners (� 373k) and the Engineering and Physical Sciences Research Council (�221k). The results will feed into the design process for Offshore Wind Turbines almostimmediately.
Gudmund Reidar Eiksund - One of the best experts on this subject based on the ideXlab platform.
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a new foundation model for integrated analyses of monopile based Offshore Wind Turbines
Energy Procedia, 2017Co-Authors: Kristoffer Skjolden Skau, Ana M Page, Hans Pette Jostad, Gudmund Reidar EiksundAbstract:Abstract Offshore Wind Turbines are highly dynamic and tightly coupled systems subjected to variable cyclic loads. Designing and optimizing the support structure is a complex task, where several load scenarios have to be analysed to account for the various uncertainties. Improving the accuracy of analysis tools used in the design and optimization process can increase the reliability and thus reduce uncertainties and risks. For monopiles supporting Offshore Wind Turbines, the current design practice is to model the foundation response by API p-y curves. Discrepancies between the assumptions considered in the API p-y curves and the actual pile behaviour have been extensively identified in the literature, and their applicability to predict pile behaviour in integrated analyses of Offshore Wind Turbines has been questioned. This paper presents a new foundation model for integrated analyses of monopile-based Offshore Wind Turbines. The model is simple and hence computational efficient, but still able to reproduce key characteristic in monopile foundation behaviour that are not accounted for in the current modelling approach. The model input is based on finite element analyses of the soil and the foundation, which makes it possible to calibrate the model to different soil conditions. The basic features of the model are described and its limitations are discussed. The performance of the new foundation model is demonstrated for time histories that are representative for an Offshore Wind turbine and compared with the response from API p-y curves. In contrast to the API p-y curves, the new model can reproduce different foundation stiffness for unloading and reloading and foundation damping depending on the loading history, which is observed in real pile behaviour. A more realistic foundation modelling will lead to more accurate predicted loads, reduced uncertainties in the estimated fatigue lifetime and therefore reduced risk in the design.
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influence of soil parameters on the fatigue lifetime of Offshore Wind Turbines with monopile support structure
Energy Procedia, 2016Co-Authors: Sebastian Schafhirt, Gudmund Reidar Eiksund, Ana M Page, Michael MuskulusAbstract:Abstract Designing support structures for Offshore Wind Turbines is a complex task as these are highly dynamic systems subjected to long-term cyclic loads with variable amplitude. Long-term cyclic loading may cause stiffening or softening of the soil around the pile foundation of an Offshore Wind turbine, which leads to variations in the foundation stiffness and accumulated permanent rotation of the pile. Although variations in the foundation stiffness can negatively impact the fatigue life, the long-term variability of the soil conditions is normally not considered in the fatigue damage assessment. The main objective of this study is the investigation of the impact of changes in soil parameters on the fatigue lifetime for an Offshore Wind turbine founded in loose sand. For this purpose, a generic monopile based Offshore Wind turbine with flexible foundation model was used. The soil-pile interaction was modeled with a distributed spring model using nonlinear API p-y curves. Integrated analyses in the time domain were performed and fatigue damage was assessed in terms of a damage equivalent bending moment at mudline. The fatigue lifetime varies between -9 percent and +4 percent when considering changes in soil conditions, depending on the assumption of soil softening or stiffening, respectively. These results indicate that changes in soil parameters should be taken into account in the fatigue damage calculations of Offshore Wind Turbines for more precise fatigue lifetime estimation. Moreover, it is emphasized that more accurate modeling of soil-pile interaction is required in the design and optimization of Offshore Wind Turbines.
