scholarly journals Numerical Simulations of the Monotonic and Cyclic Behaviour of Offshore Wind Turbine Monopile Foundations in Clayey Soils

2021 ◽  
Vol 9 (9) ◽  
pp. 1036
Author(s):  
Mian Xie ◽  
Susana Lopez-Querol
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Clayey Soils ◽  
Cyclic Behaviour ◽  
Centrifuge Tests ◽  
Cumulative Rate ◽  
Number Of Cycles ◽  
The One

Most of the reported centrifuge tests available in the existing literature on offshore wind turbine foundations are focused on the behaviour of monopiles in sands, but very few studies on clayey soils can be found, due to the very long saturation and consolidation periods required to properly conduct experiments in such materials. Moreover, most of the reported numerical simulations using finite element analyses have been validated with monotonic centrifuge tests only. In this research, both monotonic and cyclic performance of offshore wind turbines in clay are validated and justified. The relationship between the monopile rotation in clays and the geometry and strength of the soil has been found and quantified. A prediction of the rotation for a high number of cycles of loading, based on the one experienced by the pile during the first cycle, can be obtained using the correlation derived in the paper. For those cases in which the rotation does not reach a steady value after a high number of cycles, the cumulative rate has been found significantly larger than the prediction conducted with standard analytical methods. A new design methodology for the design of offshore monopile foundations in clay is presented.

Offshore Wind Turbine Mono-Bucket Foundations in Sand

2021 ◽  
Author(s):  
Han Eng Low ◽  
Fangyuan Zhu ◽  
Henning Mohr ◽  
Phillip Watson ◽  
Carl Erbrich ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Large Rotation ◽  
Bucket Foundation ◽  
Dense Sand ◽  
Centrifuge Model ◽  
Centrifuge Tests ◽  
Rotational Response ◽  
Centrifuge Model Tests

Abstract Single (or mono) suction buckets have been put forward by others as possible offshore wind turbine (OWT) foundations. This paper presents a series of centrifuge model tests conducted in dense sand to investigate their monotonic response for a range of drainage conditions. The results from the centrifuge tests suggest that the mono-bucket rotational response at large rotation in dense sand is dependent on drainage conditions but does not seem to be affected by the contact condition between the bucket invert and the seabed. A final comparison between results from an equivalent set of uplift tests suggests, however, that multi-bucket foundation systems are likely to be more efficient foundation solutions, although suggestions are made which might improve mono-bucket foundation response.

Model Test of Integrated Floating Transport Technology of Offshore Wind Turbines With Composite Bucket Foundation

2018 ◽  
Author(s):  
Hongyan Ding ◽  
Lingqian Meng ◽  
Puyang Zhang ◽  
Conghuan Le
Keyword(s):  
Wind Turbine ◽  
Contact Force ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Bucket Foundation ◽  
Offshore Wind Turbines ◽  
Continuous Innovation ◽  
One Step ◽  
The One ◽  
The Relationship

With continuous innovation and development of the wind power technology, the offshore wind turbine is rapidly developing. However, it also has difficulties in construction at sea and other shortcomings. One-step installation technique of the composite bucket foundation (CBF) provides a new way to solve the difficulties in the construction of offshore wind turbine at sea. And the integrated floating transport technique of the offshore CBF is the key link in the one-step installation technique. In this paper, by controlling three factors, such as draft, wave height and speed, the contact force between the vessel and CBF in the integrated floating transportation process is studied with experimental method. The relationship and the effect between the three factors and the contact force is analyzed. The experimental results are collected and analyzed to verify the safety of the integrated floating transportation of offshore CBF.

Comparison of Cyclic P-Y Methods for Offshore Wind Turbine Monopiles Subjected to Extreme Storm Loading

2015 ◽  
Author(s):  
Wystan Carswell ◽  
Casey Fontana ◽  
Sanjay R. Arwade ◽  
Don J. DeGroot ◽  
Andrew T. Myers
Keyword(s):  
Wind Turbine ◽  
Large Diameter ◽  
Small Diameter ◽  
Design Guidelines ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Extreme Storm ◽  
Design Loads ◽  
Number Of Cycles ◽  
Pile Resistance

Approximately 75% of installed offshore wind turbines (OWTs) are supported by monopiles, a foundation whose design is dominated by lateral loading. Monopiles are typically designed using the p-y method which models soil-pile resistance using decoupled, nonlinear elastic Winkler springs. Because cyclic soil behavior is difficult to predict, the cyclic p-y method accounts for cyclic soil-pile interaction using a quasistatic analysis with cyclic p-y curves representing lower-bound soil resistance. This paper compares the Matlock (1970) and Dunnavant & O’Neill (1989) p-y curve methods, and the p-y degradation models from Rajashree & Sundaravadivelu (1996) and Dunnavant & O’Neill (1989) for a 6 m diameter monopile in stiff clay subjected to storm loading. Because the Matlock (1970) cyclic p-y curves are independent of the number of load cycles, the static p-y curves were used in conjunction with the Rajashree & Sundaravadivelu (1996) p-y degradation method in order to take number of cycles into account. All of the p-y methods were developed for small diameter piles, therefore it should be noted that the extrapolation of these methods for large diameter OWT monopiles may not be physically accurate; however, the Matlock (1970) curves are still the curves predominantly recommended in OWT design guidelines. The National Renewable Energy Laboratory wind turbine analysis program FAST was used to produce mudline design loads representative of extreme storm loading. These design loads were used as the load input to cyclic p-y analysis. Deformed pile shapes as a result of the design load are compared for each of the cyclic p-y methods as well as pile head displacement and rotation and degradation of soil-pile resistance with increasing number of cycles.

Experimental and Numerical Study of the Influence of Drag Coefficient on Snap Loads in Mooring Lines of a Floating Offshore Wind Turbine

2021 ◽  
Author(s):  
Brendan Guillouzouic ◽  
François Pétrié ◽  
Vincent Lafon ◽  
Fabien Fremont
Keyword(s):  
Numerical Simulations ◽  
Drag Coefficient ◽  
Wind Turbine ◽  
Scale Effects ◽  
Numerical Study ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Bodies ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbine

Abstract Mooring is one of the key components of a floating offshore wind turbine since the mooring rupture may lead to the total loss of one or even several turbines in a farm. Even if a large experience in moorings of floating bodies was gained in the oil & gas industry, the renewable energies face new challenges such as reducing the cost as much as possible, reducing the footprint to limit environmental impact or avoid any interference between mooring lines and electrical cables in a farm composed of several tens of turbines. Those constraints may lead to designs suffering snap loads which shall be avoided as far as practicable or addressed with a particular attention, as this quasi-instantaneous stretching of the mooring lines may lead to very high tensions governing the design. This paper presents the results of physical model tests and numerical simulations performed on a typical floating wind turbine concept of semi-submersible type. Both qualitative and quantitative comparisons are performed. The objective is to provide guidelines for FOWT mooring designers regarding the selection of the drag coefficient to consider. A very significant influence of the line’s drag coefficient, on both the probability of occurrence and the magnitude of snap loads, was found. This subject is hereby fully documented on a given case study and general discussions on scale effects, marine growth effects and other parameters are also made. The numerical simulations were performed using the dynamic analysis software ‘OrcaFlex’. The experiments have been carried out by Océanide, in south of France.

Numerical Study for a Catamaran Gripper-Monopile Mechanism of a Novel Offshore Wind Turbine Assembly Installation Procedure

2017 ◽  
Author(s):  
Lars Ivar Hatledal ◽  
Houxiang Zhang ◽  
Karl Henning Halse ◽  
Hans Petter Hildre
Keyword(s):  
Numerical Simulations ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Numerical Study ◽  
Weather Conditions ◽  
Rolling Contact ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Contact Points ◽  
Turbine Installation

Current methods for installation of offshore wind turbines are all sensitive to the weather conditions and the present cost level of offshore wind power is more than twice the cost of land-based units, increasing with water depth. This paper presents numerical simulations of a novel experimental gripper design to reduce the environmental effects applied to a catamaran type of vessel during wind turbine installation. In SFI MOVE project in NTNU Aalesund, our team proposed a novel wind turbine installation process. A new catamaran vessel will carry pre-assembled wind turbines to the installation location. Two new designed grippers on the deck will make a lifting operation to install the wind turbine onto the turbine foundation. Three prismatic grippers with several rolling contact points at the end are attached in an arc at the catamaran’s aft, designed to grasp the turbine foundation in order to make a connection between the two in the horizontal plane. This paper will only emphasize the contact responses between the turbine foundation and the three grippers during the wind turbine installation process. Numerical simulations are carried out using the virtual prototyping framework Vicosim which is developed by NTNU Aalesund. The simulation results show validation of a key part of the proposed new wind turbine installation idea.

scholarly journals Centrifuge Modeling for the Evaluation of the Cyclic Behavior of Offshore Wind Turbine with Tripod Foundation

2021 ◽  
Vol 11 (4) ◽  
pp. 1718
Author(s):  
Yeong-Hoon Jeong ◽  
Seong-Won Lee ◽  
Jae-Hyun Kim
Keyword(s):  
Wind Turbine ◽  
Scaling Law ◽  
Centrifuge Modeling ◽  
Offshore Wind ◽  
Cyclic Behavior ◽  
Soil Conditions ◽  
Offshore Wind Turbine ◽  
Simple Method ◽  
Number Of Cycles

In this study, the cyclic responses of an offshore wind turbine with a tripod foundation installed on an actual site were evaluated in a centrifuge. To understand the behavior of the turbine at the site, the site soil conditions, environmental loads, and real offshore wind turbine structure installed at the actual site were modeled by considering the centrifuge scaling law. From a series of cyclic loading tests, the cyclic responses of the tripod foundation were evaluated in terms of temporary/permanent displacements and cyclic stiffness. Moreover, the long-term behavior of the tripod foundation was predicted from the experimental results. The test results showed that the initial stiffness of the soil–foundation system decreased as the loading amplitude increased and that the stiffness increased with the number of cycles due to soil densification. The findings revealed that the cyclic behaviors of the tripod were more affected by the load amplitude than the number of cycles. In addition, the permanent rotation increased logarithmically with the number of cycles. A simple method to predict the displacement and change in the foundation stiffness of the actual wind turbine is proposed based on the results of the model tests. The results of this study also provide key insights into the long-term cyclic behavior of tripod foundations for offshore wind turbines.

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