Effect of monopile foundation modeling on the structural response of a 5-MW offshore wind turbine tower

Jung, Sungmoon; Kim, Sung-Ryul; Patil, Atul; Hung, Le Chi

doi:10.1016/j.oceaneng.2015.09.033

Cited by 104 publications

(53 citation statements)

References 20 publications

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“…In engineering practice, during the dynamic analysis of the whole structure of offshore wind turbine, the load-displacement response of a monopile foundation is often simplified to be a foundation stiffness matrix; accordingly, the natural frequency and the load-displacement response of the support structure can be calculated (Figure 7) [36][37][38][39][40]. Arany et al [39] considered that the vertical foundation stiffness for the monopile foundation of an offshore turbine is much higher than the foundation stiffness in other directions; therefore, simple calculations of foundation stiffness can disregard the influence of vertical foundation stiffness.…”

Section: Foundation Stiffness Of Monopilementioning

confidence: 99%

Section: Foundation Stiffness Of Monopilementioning

confidence: 99%

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An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

2017

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Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The so-called p-y curves method is suggested in the existing design recommendations to determine the behavior of monopiles unprotected against scour and the reduction of effective soil stress is accounted for by the extreme scour depth. This conservative design approach does not consider the geometry of the scour hole and the effect of pile diameter on the soil resistance. An underestimated foundation stiffness would be obtained, thereby influencing the predicted overall response of the support structure of an offshore wind turbine. In this study, we calculated the load-deformation response and foundation stiffness of a monopile when scour occurred. The influence of pile diameter on the initial modulus of subgrade reaction, and the modification of the ultimate soil resistance of a monopile subject to scour are evaluated. The commercial software BLADED was used to simulate the dynamic response of the reference offshore wind turbine with monopile unprotected against scour at Chang-Bin offshore wind farm in Taiwan Strait. The results showed that when the p-y curve suggested by existing design regulation was used to calculate the load-deformation response, the foundation stiffness was underestimated where the scour depth was greater than the pile diameter, but the foundation stiffness was overestimated when the scour depth was less than the pile diameter.

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Section: Foundation Stiffness Of Monopilementioning

confidence: 99%

Section: Foundation Stiffness Of Monopilementioning

confidence: 99%

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

2017

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“…The elastic stiffness and the p-y curves gave comparable predicted natural frequencies. In addition, Jung et al (2015) carried out a comparison between three foundation models with focus on the foundation stiffness. In the study, the foundation response was represented by a stiffness matrix at mud-line, distributed p-y elements, and a FE model of the soil volume.…”

Section: Numerical Studies Investigating Effects Of Soil Stiffness Anmentioning

confidence: 99%

Effect of foundation modelling on the fatigue lifetime of a monopile-based offshore wind turbine

et al. 2017

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Abstract. Several studies have emphasized the importance of modelling foundation response with representative damping and stiffness characteristics in integrated analyses of offshore wind turbines (OWTs). For the monopile foundation, the industry standard for pile analysis has shown to be inaccurate, and alternative models that simulate foundation behaviour more accurately are needed. As fatigue damage is a critical factor in the design phase, this study investigates how four different soil-foundation models affect the fatigue damage of an OWT with a monopile foundation. This study shows how both stiffness and damping properties have a noticeable effect on the fatigue damage, in particular for idling cases. At mud-line, accumulated fatigue damage varied up to 22 % depending on the foundation model used.

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“…() The mechanical models are calibrated against p‐y curves provided by the American Petroleum Institute (API) . Although the p‐y methodology has been proposed many years back,() and its limitations have been reported in the literature regarding OWT,() it is still a common tool used in the industry . Furthermore, it should be highlighted that the aim of the current study is to show the ability of the mechanical models presented herein to be calibrated against any kind of soil‐pile response curves and that they are able to provide a wide range of hysteretic energy dissipation level under the same effective stiffness.…”

Section: Introductionmentioning

confidence: 95%

Nonlinear soil‐pile interaction for offshore wind turbines

Μάρκου

Kaynia

2018

Wind Energy

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The current work presents a parametric study, which involves different generalized nonlinear mechanical formulations with different damping characteristics to account for the interaction between a monopile-supported offshore wind turbine and the surrounding soil. The novelty of the study lies in the fact that recently developed nonlinear mechanical models used so far for the simulation of high-damping rubber isolators are introduced to describe the nonlinear hysteretic soil behavior. More specifically, the first generalized mechanical model consists of a combination of elastoplastic and trilinear elastic elements (labeled as model 3), while the second model consists of trilinear hysteretic models connected in parallel with trilinear elastic springs and hysteretic dampers used to ensure that the unloading stiffness will be as close as possible to the initial stiffness of the system (labeled as model 4). These newly developed models are compared with well-known models within the industry, namely, a model that comprises elastoplastic elements (labeled as model 1) and a model that comprises trilinear elastic springs (labeled as model 2). All these models provide exactly the same effective stiffness, but on the other hand different levels of damping are involved in each one of them. The goal of the present work is 3-fold, introducing novel mechanical models for the simulation of soil behavior, to investigate the effect of different soil damping levels in the response of offshore wind turbines and to highlight the limitations of the commonly used models within the industry. To this end, the differences between the response due to different levels of damping characteristics and modeling approaches are shown, highlighting the importance of soil damping in the overall response of the system. KEYWORDS monopile, nonlinearity, plasticity, p-y curves, soil-pile interaction, trilinear hysteretic model, Winkler's model INTRODUCTIONBecause winds are stronger and steadier in the sea, offshore wind turbines (OWT) have attracted additional attention. 1 The most common type of wind turbine is the horizontal axis wind turbine, which consists of (1) the rotor, (2) the drive train, (3) the nacelle and the main frame, (4) the tower, (5) the foundation, (6) the machine controls, and (7) the balance of the electrical system. 2 Furthermore, different types of wind turbine foundation exist: (1) monopile systems, (2) tripod systems, (3) jacket structures, (4) suction caissons, (5) gravity-based foundations, and (6) floating systems. 3Most of the OWT are currently supported on monopiles partly for economic reasons. 4The main dynamic excitation of OWT is caused by (1) the wind, (2) the waves, (3) the vibration due to imbalances of the rotor (1P), and (4) the blade shadowing effect (2P/3P). The main sources of damping for OWT are (1) the aerodynamic, (2) the structural, (3) the nonlinear soil response, (4) the hydrodynamic, and (5) the radiation damping in soil. 3 In the case of OWT founded on monopile systems the natural frequencies of the ove...

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Effect of monopile foundation modeling on the structural response of a 5-MW offshore wind turbine tower

Cited by 104 publications

References 20 publications

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

Effect of foundation modelling on the fatigue lifetime of a monopile-based offshore wind turbine

Nonlinear soil‐pile interaction for offshore wind turbines

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