Soil–structure reliability of offshore wind turbine monopile foundations

Carswell, Wystan; Arwade, Sanjay R.; DeGroot, Don J.; Lackner, Matthew A.

doi:10.1002/we.1710

Cited by 85 publications

(47 citation statements)

References 18 publications

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“…Although a definitive answer as to whether earthquake loads are design driving for the two structures under study can be given only considering sitespecific conditions, these results substantiate the need for an accurate seismic assessment when installing offshore HAWTs in seismically active areas. In this context, refined seismic analyses should be carried out, considering vertical ground motion, variation of earthquake acceleration through soil layers [15], potential misalignment between wind and wave loads during earthquake shaking, and other important issues such as sensitivity to different models of p − y curves [37] and potential uncertainties in soil properties [39], alterations of the foundation stiffness due to on May 12, 2018 http://rsta.royalsocietypublishing.org/ Downloaded from…”

Section: Discussionmentioning

confidence: 99%

Seismic analysis of offshore wind turbines on bottom-fixed support structures

Alati

Failla

Arena

2015

Phil. Trans. R. Soc. A.

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This study investigates the seismic response of a horizontal axis wind turbine on two bottom-fixed support structures for transitional water depths (30-60 m), a tripod and a jacket, both resting on pile foundations. Fully coupled, nonlinear time-domain simulations on full system models are carried out under combined wind-wave-earthquake loadings, for different load cases, considering fixed and flexible foundation models. It is shown that earthquake loading may cause a significant increase of stress resultant demands, even for moderate peak ground accelerations, and that fully coupled nonlinear time-domain simulations on full system models are essential to capture relevant information on the moment demand in the rotor blades, which cannot be predicted by analyses on simplified models allowed by existing standards. A comparison with some typical design load cases substantiates the need for an accurate seismic assessment in sites at risk from earthquakes.

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Section: Discussionmentioning

confidence: 99%

Seismic analysis of offshore wind turbines on bottom-fixed support structures

Alati

Failla

Arena

2015

Phil. Trans. R. Soc. A.

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“…Whereas the distribution of mass is usually well known, the stiffness and damping properties are often uncertain. In particular, the site‐specific soil properties are associated with large uncertainties, and they may change throughout the lifetime of the OWT . Therefore, the true modal characteristics of monopile OWTs are generally not known until they are installed .…”

Section: Low‐fidelity Owt Modelmentioning

confidence: 99%

Wave disturbance rejection for monopile offshore wind turbines

et al. 2018

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The dimensions of offshore wind turbine (OWT) support structures are governed by fatigue considerations. For 6‐ to 10‐MW OWTs, wave loads are often dominating in terms of fatigue utilization. The present work proposes a control scheme to reduce the wave‐induced fatigue loads in OWT support structures. The control scheme applies collective pitch control to increase both the damping and stiffness of the fore‐aft vibration modes. With conventional active tower damping, efficient wave disturbance rejection is restricted to a narrow frequency range around the first fore‐aft modal frequency. The proposed control scheme achieves efficient wave disturbance rejection across a broader frequency range. Here, tower feedback control is implemented via an auxiliary control loop. Based on a low‐fidelity model, the effect of the tower feedback loop on the stability margins of the basic controller is analysed. The results show that, within certain boundaries, the stability margins are improved by the stiffness term in the tower feedback loop. Consequently, the need to reduce the bandwidth of the basic controller to accommodate tower feedback control is relaxed. Based on time‐domain simulations carried out in an aero‐hydro‐servo‐elastic simulation tool, the lifetime effects of the proposed control scheme are analysed. Compared with conventional active tower damping, a more favourable trade‐off between adverse side effects and the support structure's fatigue damage is achieved with the proposed control scheme.

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“…However, compared with the axial loads, the lateral loads are considered governing, as mentioned in several design guidelines (e.g. GL 2005; API 2010; DNV 2011) and documented by many researchers (Achmus 2010;Leblanc, Byrne, and Houlsby 2010;Malhotra 2011;Peng, Clarke, and Rouainia 2011;Bhattacharya et al 2012;Kuo, Achmus, and Abdel-Rahman 2012;Haiderali, Cilingir, and Madabhushi 2013;Lombardi, Bhattacharya, and Wood 2013;Zhu, Byrne, and Houlsby 2013;Nicolai and Ibsen 2014;Carswell et al 2015). For OWT monopile foundations, the required embedment length is dictated by the applied horizontal loads and moments.…”

Section: Monopile Embedment Length and Foundation Stabilitymentioning

confidence: 99%

Analysis and Design of Monopile Foundations for Offshore Wind-Turbine Structures

Arshad

O’Kelly

2015

Marine Georesources & Geotechnology

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Offshore wind turbines (OWTs) are generally supported by large-diameter monopiles, with the combination of axial forces, lateral forces, bending moments and torsional moments generated by the OWT structure and various environmental factors resisted by earth pressures mobilized in the soil foundation. The loading on the monopile foundation is essentially cyclic in nature and typically low-amplitude. This state-of-the-art review paper presents details on the geometric Downloaded by [New York University] at 00:02 29 July 2015 2 design, nominal size, and structural and environmental loading for existing and planned OWT structures supported by monopile foundations. Pertinent ocean-environment loading conditions, including methods of calculation using site-specific data, are described along with wave particle kinematics, focusing on correlations between loading frequency and natural vibration frequency of the OWT structure. Existing methods for modelling soil under cyclic loading are reviewed, focusing in particular on strain accumulation models that consider pile-soil interaction under cyclic lateral loading. Inherent limitations/shortcomings of these models for the analyses and design of existing and planned OWT monopile foundations are discussed. A design example of an OWT support structure having a monopile foundation system is presented. Target areas for further research by the wind-energy sector are identified which would facilitate the development of improved analyses/design methods for offshore monopiles.

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Soil–structure reliability of offshore wind turbine monopile foundations

Cited by 85 publications

References 18 publications

Seismic analysis of offshore wind turbines on bottom-fixed support structures

Seismic analysis of offshore wind turbines on bottom-fixed support structures

Wave disturbance rejection for monopile offshore wind turbines

Analysis and Design of Monopile Foundations for Offshore Wind-Turbine Structures

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