Effects of soil–structure interaction on real time dynamic response of offshore wind turbines on monopiles

Damgaard, Mads; Zania, Varvara; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo

doi:10.1016/j.engstruct.2014.06.006

Cited by 82 publications

(44 citation statements)

References 28 publications

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“…Nevertheless, these assumptions may seem reasonable for many offshore wind turbine locations where the lower part of the monopile is placed in a relatively stiff soil layer that prevents pile deflections during normal turbine operation. In addition, it should be noted that a three-dimensional coupled BE/ FE model [32] of a monopile embedded in a viscoelastic soil layer shows almost a constant impedance component for torsional vibrations in the physical frequency range f 0; 8 Hz ∈ [ ] that equals the static torsional pile stiffness [33]. For that reason, the static torsional pile stiffness enters Eq.…”

Section: Physical Modelling Of Unbounded Soil and Monopilementioning

confidence: 99%

A probabilistic analysis of the dynamic response of monopile foundations: Soil variability and its consequences

Damgaard

Andersen

Ibsen

et al. 2015

Probabilistic Engineering Mechanics

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Section: Physical Modelling Of Unbounded Soil and Monopilementioning

confidence: 99%

A probabilistic analysis of the dynamic response of monopile foundations: Soil variability and its consequences

Damgaard

Andersen

Ibsen

et al. 2015

Probabilistic Engineering Mechanics

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“…It must be mentioned that these springs are not only frequency dependent but also change with cycles of loading due to dynamic soil structure interaction. Further details on the dynamic interaction can be found in (Bhattacharya et al 2013b;Bhattacharya et al 2013c;Bhattacharya et al 2013a;Lombardi et al 2013;Zania 2014;Damgaard et al 2014) Randolph (1981), slender piles, both for homogeneous and linear inhomogeneous soils Table 3. Stiffness formulae by different researchers for rigid piles in various soil profiles.…”

Section: Foundation Stiffness Of Monopilesmentioning

confidence: 99%

Design of monopiles for offshore wind turbines in 10 steps

Arany

Bhattacharya

Macdonald

et al. 2017

Soil Dynamics and Earthquake Engineering

286

157

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ABSTRACT:A simplified design procedure for foundations of offshore wind turbines is often useful as it can provide the types and sizes of foundation required to carry out financial viability analysis of a project and can also be used for tender design. This paper presents a simplified way of carrying out the design of monopiles based on necessary data (i.e. the least amount of data), namely site characteristics (wind speed at reference height, wind turbulence intensity, water depth, wave height and wave period), turbine characteristics (rated power, rated wind speed, rotor diameter, cut-in and cut-out -upper limit of the 1P frequency range -fixed base (cantilever beam) natural frequency of the tower -characteristic yield strength -gravitational constant -distance from zero shear force location to pile toe -air gap between the highest expected wave crest level and the platform -wave number 0 -equivalent stiffness of first tower mode ℎ -horizontal modulus of subgrade reaction -total structural mass, also strain accumulation exponent 0 -equivalent mass of first tower mode -mass of the pile -mass of the rotor-nacelle assembly -mass of the tower -mass of the transition piece ℎ -horizontal coefficient of subgrade reaction ℎ1 -coefficient of subgrade reaction at the first load cycle ℎ -coefficient of subgrade reaction after N load cycles -shape parameter of Weibull distribution -undrained shear strength of soil , , -time, also degradation parameters degradation model -grout thickness -pile wall thickness -tower wall thickness -wall thickness of the transition piece -transition piece wall thickness -turbulent wind speed component -extreme gust speed ,

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“…Finally, the current work emphasizes on the importance that the proper simulation of the soil‐pile interaction phenomena has for the estimation of the fatigue lifetime of OWTs; see also the literature. ()…”

Section: Discussionmentioning

confidence: 99%

“…Damgaard et al used semi‐analytical frequency‐domain solutions to evaluate the dynamic impedance functions of the pile‐soil system to calibrate a lumped mass model for integration into an aeroelastic multibody code. They used 3 different models for the monopile foundation, namely, the apparent fixity model, a fixed support model at the seabed level, and a coupled lumped‐parameter model.…”

Section: Introductionmentioning

confidence: 99%

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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Effects of soil–structure interaction on real time dynamic response of offshore wind turbines on monopiles

Cited by 82 publications

References 28 publications

A probabilistic analysis of the dynamic response of monopile foundations: Soil variability and its consequences

A probabilistic analysis of the dynamic response of monopile foundations: Soil variability and its consequences

Design of monopiles for offshore wind turbines in 10 steps

Nonlinear soil‐pile interaction for offshore wind turbines

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