Monopile head stiffness for servicibility limit state calculations in assessing the natural frequency of offshore wind turbines

Aissa, Mohammed Hemza; Bouzid, Djillali Amar; Bhattacharya, Subhamoy

doi:10.1080/19386362.2016.1270794

Cited by 22 publications

(9 citation statements)

References 27 publications

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“…It is observed that the f values under the condition of deformable ground are approximately 25% lower than the f on rigid ground. With the increase in D r , the f presents a slight increase because the pile head stiffness increases with the increase in D r [41]. However, the maximum f values under different ground conditions are very similar (10.36 Hz when D r = 20%, 10.38 Hz when D r = 40%, and 10.48 Hz when D r = 60%).…”

Section: Natural Frequencymentioning

confidence: 92%

Dynamic Performance of Monopile-Supported Wind Turbines (MWTs) under Different Operating and Ground Conditions

Xiao,

Liu,

Lin

2023

Energies

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A monopile is the most popular foundation type for wind turbines. However, the dynamic performance of monopile-supported wind turbines under different operating and ground conditions is not fully understood. In this study, an integrated monopile-supported wind turbine model in a wind tunnel was employed to jointly simulate the operating and ground conditions. A series of wind tunnel tests were designed and performed to investigate the dynamic performance of monopile-supported wind turbines. These tests included seven operating conditions (seven wind speeds and corresponding rotor speeds) and four ground conditions (one fixed ground condition and three deformable ground conditions with different soil relative densities). According to the test results, the structural responses and dynamic characteristics were analyzed and discussed. This shows that the assumption of fixed-base support significantly overestimates the natural frequency but underestimates the global damping ratio. With the increase in soil relative density, the natural frequency slightly increases, while the damping ratio decreases more significantly. With the increase in the wind speed and rotor speed, the increase in global damping is larger on softer ground. A regression analysis was performed to estimate the global damping ratio under different operating and ground conditions.

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Section: Natural Frequencymentioning

confidence: 92%

Dynamic Performance of Monopile-Supported Wind Turbines (MWTs) under Different Operating and Ground Conditions

Xiao,

Liu,

Lin

2023

Energies

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“…where m T and m S are the tower and substructure masses, respectively. For more precise representation of the (substructure + tower) flexural rigidity EI TS , Amar Bouzid et al [3] and Aissa et al [2] proposed the following formula:…”

Section: Approximate Owt Modeling For Dynamic Analysismentioning

confidence: 99%

“…where E is the steel Young's modulus, which is equal to both E T and E p . The factor λ av , which depends on the ratio m, has been determined by Aissa et al (2018) as the average value of three other factors. These are…”

Section: Appendix A: Parameter Expressions Allowing To Calculate the ...mentioning

confidence: 99%

“…The most widely adopted foundation is the monopile, which is a large-diameter hollow steel driven pile with a diameter D p ranging from 3 to 8 m and a length to diameter (L p ⁄D p ) smaller than 8. This is because this type of foundation is easy and convenient to construct [2,3]. However, monopile diameters increased considerably over the past decades and are expected to grow further in the future due to the increasing rotor diameters required for more efficiency in wind power.…”

Section: Introductionmentioning

confidence: 99%

“…It is generally accepted that the dynamic characteristics, especially the first natural frequency (1st NF) of an OWT, are affected by the soil-monopile interaction [2,3]. When the BNWF model fails to adequately capture the lateral behavior of a large-diameter monopile, an inaccurate monopile head stiffness is produced, and consequently the OWT design is unsafe.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evaluation of sand p–y curves by predicting both monopile lateral response and OWT natural frequency

Amel

Bouzid

Bhattacharya

et al. 2022

Studia Geotechnica Et Mechanica

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Extending the use of the p–y curves included in the regulation codes API and DNV to design large-diameter monopiles supporting offshore wind turbines (OWTs) was unsuccessful as it resulted in an inaccurate estimation of the monopile behavior. This had prompted many investigators to propose formulations to enhance the performances of Winkler model. In this paper, two case studies are considered. A case consisting of an OWT at Horns Rev (Denmark) supported by a monopile in a sandy soil was studied first. Taking the FEA using ABAQUS as reference, results of WILDOWER 1.0 (a Winkler computer code) using the recently proposed p–y curves giving design parameters were plotted and evaluated. In order to see the ability of proposed p–y curves to predict the monopile head movements, and consequently the first natural frequency (1st NF), a second case study consisting of a monopile supporting an OWT at North Hoyle (UK) was selected. The monopile head stiffness in terms of lateral, rocking, and cross-coupling stiffness coefficients, necessary for the 1st NF, were computed using both ABAQUS and WILDPOWER 1.0. Comparisons with the measured 1st NF showed that with the exception of one p–y model, none of other proposed Winkler methods is able to predict accurately this parameter.

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Study on Failure Mechanism and Soil Resistance for Laterally-Loaded Large-Diameter Monopiles

et al. 2023

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Monopile head stiffness for servicibility limit state calculations in assessing the natural frequency of offshore wind turbines

Cited by 22 publications

References 27 publications

Dynamic Performance of Monopile-Supported Wind Turbines (MWTs) under Different Operating and Ground Conditions

Dynamic Performance of Monopile-Supported Wind Turbines (MWTs) under Different Operating and Ground Conditions

Evaluation of sand p–y curves by predicting both monopile lateral response and OWT natural frequency

Study on Failure Mechanism and Soil Resistance for Laterally-Loaded Large-Diameter Monopiles

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