Numerical Analysis of Large-Diameter Monopiles in Dense Sand Supporting Offshore Wind Turbines

Ahmed, Sheikh Sharif; Hawlader, Bipul

doi:10.1061/(asce)gm.1943-5622.0000633

Cited by 90 publications

(22 citation statements)

References 43 publications

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“…Although there is some underestimation of the response of 6 m pile at lager deflection, the maximum difference is less than 10%. Intergranular strain concept [29] Parameter controlling initial shear modulus upon 180° strain path reversal, 8…”

Section: Validation Of the Fe Modelmentioning

confidence: 99%

Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densities

Wang

Hong

et al. 2021

JMSE

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The large-diameter monopiles are the most preferred foundation used in offshore wind farms. However, the influence of pile diameter and aspect ratio on the lateral bearing behavior of monopiles in sand with different relative densities has not been systematically studied. This study presents a series of well-calibrated finite-element (FE) analyses using an advanced state dependent constitutive model. The FE model was first validated against the centrifuge tests on the large-diameter monopiles. Parametric studies were performed on rigid piles with different diameters (D = 4–10 m) and aspect ratios (L/D = 3–7.5) under a wide range of loading heights (e = 5–100 m) in sands with different relative densities (Dr = 40%, 65%, 80%). The API and PISA p-y models were systematically compared and evaluated against the FE simulation results. The numerical results revealed a rigid rotation failure mechanism of the rigid pile, which is independent of pile diameter and aspect ratio. The computed soil pressure coefficient (K = p/Dσ′v) of different diameter piles at same rotation is a function of z/L (z is depth) rather than z/D. The force–moment diagrams at different deflections were quantified in sands of different relative density. Based on the observed pile–soil interaction mechanism, a simple design model was proposed to calculate the combined capacity of rigid piles.

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Section: Validation Of the Fe Modelmentioning

confidence: 99%

Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densities

Wang

Hong

et al. 2021

JMSE

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“…10–13 Many kinds of nonlinear spring models were proposed to simulate the dynamic soil–structure interaction: distributed spring model, 9,11 three-spring model (lateral spring, rotational spring and vertical spring), 12 four-spring model (lateral spring, rotational spring, rotational–lateral coupled spring and vertical spring) 2,5 and simplified lumped mass single-degree-of-freedom (SDOF) model. 13 Based on the scaled model test and the FEA results, the following conclusion was drawn: long-term cyclic loading may cause either stiffening or softening of the soil around the pile foundation of an OWT, that is, stiffening for the sandy soil 9,14–18 and softening for the clayey soil. 2,3,19…”

Section: Introductionmentioning

confidence: 99%

“…Based on the scaled model test and the FEA results, the following conclusion was drawn: long-term cyclic loading may cause either stiffening or softening of the soil around the pile foundation of an OWT, i.e. stiffening for the sandy soil [14][15][16][17][18][19] and softening for the clayey soil [2,3,20].…”

Section: Introductionmentioning

confidence: 99%

Support condition monitoring of offshore wind turbines using model updating techniques

Nikitas

Zhang

et al. 2019

Structural Health Monitoring

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The offshore wind turbines are dynamically sensitive, whose fundamental frequency can be very close to the forcing frequencies activated by the environmental and turbine loads. Minor changes of support conditions may lead to the shift of natural frequencies, and this could be disastrous if resonance happens. To monitor the support conditions and thus to enhance the safety of offshore wind turbines, a model updating method is developed in this study. A hybrid sensing system was fabricated and set up in the laboratory to investigate the long-term dynamic behaviour of the offshore wind turbine system with monopile foundation in sandy deposits. A finite element model was constructed to simulate structural behaviours of the offshore wind turbine system. Distributed nonlinear springs and a roller boundary condition are used to model the soil–structure interaction properties. The finite element model and the test results were used to analyse the variation of the support condition of the monopile, through an finite element model updating process using estimation of distribution algorithms. The results show that the fundamental frequency of the test model increases after a period under cyclic loading, which is attributed to the compaction of the surrounding sand instead of local damage of the structure. The hybrid sensing system is reliable to detect both the acceleration and strain responses of the offshore wind turbine model and can be potentially applied to the remote monitoring of real offshore wind turbines. The estimation of distribution algorithm–based model updating technique is demonstrated to be successful for the support condition monitoring of the offshore wind turbine system, which is potentially useful for other model updating and condition monitoring applications.

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“…In order to overcome this limitation, attempts have been made in recent studies to allow for the mobilisation of 𝜑 ′ and 𝜓 with relative density, mean effective stress and accumulated plastic shear strain (Guo & Stolle, 2005;Robert, 2010;Roy et al 2015). For instance, Ahmed & Hawlader (2016) employed a modified MC model (MMC) to simulate the response of offshore monopile foundations in dense sands. This paper reports detailed three-dimensional numerical analyses of TPJ foundations subjected to torque in dense sands.…”

Section: Introductionmentioning

confidence: 99%

Torque-Transferring Characteristics of Offshore Tetrapod Piled Jacket Foundations in Dense Sand

et al. 2023

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Tetrapod piled jacket (TPJ) foundations supporting offshore wind turbines (OWTs) tend to subject to significant torque caused by eccentric loading from wind, wave or accidental vessel impact. This paper presents comprehensive three-dimensional numerical analyses to investigate TPJ's performance under torsional loading, considering in particular the distribution of local torque and rotation over pile shafts and the underlying torsional load transfer mechanism. A modified Mohr-Coulomb model for dense sands was implemented in ABAQUS/Standard that captured the evolution of friction angle and dilation angles against the accumulated plastic shear strain. Resultsshow that the torque imposed at the head of TPJ foundation could trigger soil reactions of torsional resistance and horizontal force in individual piles; higher pile spacing-to-diameter ratios mitigate the influence of torsional loads. A pressure-dependent torsional load transfer model was proposed that takes into account the effects of pile-sand relative stiffness and sand's relative density. The model can be employed to predict TPJ's response under torsional loading and improve its practical design.

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Numerical Analysis of Large-Diameter Monopiles in Dense Sand Supporting Offshore Wind Turbines

Cited by 90 publications

References 43 publications

Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densities

Influence of Pile Diameter and Aspect Ratio on the Lateral Response of Monopiles in Sand with Different Relative Densities

Support condition monitoring of offshore wind turbines using model updating techniques

Torque-Transferring Characteristics of Offshore Tetrapod Piled Jacket Foundations in Dense Sand

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