Strength, stiffness, resonance and the design of offshore wind turbine monopiles

Myers, Andrew C.; Arwade, Sanjay R.; Valamanesh, V.; Hallowell, Spencer T.; Carswell, Wystan

doi:10.1016/j.engstruct.2015.06.021

Cited by 30 publications

(11 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The monopile designs are simplified further by reducing the geometric design space to three geometric parameters: diameter, thickness and embedment depth. For each location and water depth, the selected design is the lightest combination of these three parameters, which satisfies five design constraints: (i) monopile drivability, (ii) resonance avoidance, following the method in Myers et al , (iii) ultimate moment strength and serviceability under DLC 1.6a, (iv) ultimate strength and serviceability under DLC 6.1a and (v) ultimate strength and serviceability under DLC 6.2a. Drivability constraints are enforced on the monopile diameter‐to‐thickness ratio, which is limited to a maximum value of 150 to avoid buckling during the driving process per recommendations by API .…”

Section: Monopile Designmentioning

confidence: 99%

“…The structural frequency of each monopile geometry combination satisfying the drivability limit of D / t being less than 150 is compared with the operational frequency ranges of the OWT, and any frequency that overlaps these ranges is eliminated to avoid operational resonance. The specifics of this procedure are detailed by Myers et al and consider the flexibility of the soil using API P–Y springs for soil characteristics broadly representative of the US Atlantic coast (Figure b). The monopile geometries that conform to the drivability and resonance avoidance design constraints are then modeled in fast for operational and extreme environmental conditions.…”

Section: Monopile Designmentioning

confidence: 99%

“…Flexibility in the foundation is considered via the apparent fixity method, as shown in Figure c. More details of this approach are provided by Myers et al …”

Section: Monopile Designmentioning

confidence: 99%

See 2 more Smart Citations

Site-specific variability of load extremes of offshore wind turbines exposed to hurricane risk and breaking waves

Hallowell

Myers

2016

Wind Energ.

Self Cite

View full text Add to dashboard Cite

Much of the US offshore wind energy resource is located in shallow water off the Atlantic coast, which is exposed to both hurricanes and breaking waves. Current practice in offshore wind turbine (OWT) design is to realize a target structural reliability by amplifying loads using fixed load factors that do not vary with structural or site characteristics. Given that variability in both hurricane conditions and breaking waves is structure-and site-specific, the structural reliability of OWTs may vary significantly from site to site if fixed load factors are used. To understand the implications of this situation, there is a need to compare the numerical values of fixed load factors with those calculated using methods that prescribe structure-specific and site-specific load amplification that reflects variability in long-term conditions. In this paper, site-specific load amplification is considered for four Atlantic coast locations and four water depths per location and then compared with fixed load factors commonly used in the design of OWTs. The study shows that decreasing water depth and increasing hurricane exposure tend to increase the required load amplification for consistent structural reliability. Another influential factor is the mean return period at which impact loads due to breaking waves begin to dominate the loading.

show abstract

Section: Monopile Designmentioning

confidence: 99%

Section: Monopile Designmentioning

confidence: 99%

See 1 more Smart Citation

Site-specific variability of load extremes of offshore wind turbines exposed to hurricane risk and breaking waves

Hallowell

Myers

2016

Wind Energ.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The dynamic characterization, i.e. computation of the modified fundamental frequency and damping, of OWT structures including the SSI effects has been the object of study for numerous recent works [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…They found that the rotor and nacelle mass and the tower height play a crucial role on design, while the embedded depth of the monopile beyond the critical length has a marginal impact. Myers et al [18] analysed when the strength (resistance in operational and extreme conditions) or stiffness (resonance avoidance) criteria govern the design of monopiles for OWT, and presented optimum pile sections that satisfied these demands. If a fixed base was assumed, the strength criterion controlled the design; but when the soil flexibility was included, the stiffness criterion became important in two of the three studied sites, corresponding to deeper water depths.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Response of Real Offshore Wind Turbines on Monopiles in Stratified Seabed

Álamo¹,

Aznárez²,

Padrón³

et al. 2016

Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)

View full text Add to dashboard Cite

This paper studies the influence of the superstructure and foundation parameters of offshore wind turbine (OWT) systems, as well as of the soil profile, on the magnitude of the associated soil-structure interaction (SSI) phenomena. The analyses are carried out by assuming characteristic properties of real OWTs and of soil profiles based on North Sea boreholes. To do so, a simplified substructuring model is proposed for the computation of the fundamental frequency and equivalent damping of OWTs founded on monopiles including the SSI effects. The whole superstructure is reduced to a three-degrees-of-freedom system through its modal mass and height, while the foundation stiffness is represented by impedance functions. The pile impedance functions are computed by a time-harmonic integral model that makes use of Green's Functions for the layered halfspace to represent the soil behaviour, while the pile is represented by finite elements as a Timoshenko beam and treated as a load-line within the soil. The obtained results confirm the necessity of considering the SSI effects for an accurate estimation of both the fundamental frequency and equivalent damping of the soil-structure system. Regarding the pile dimensions, the pile diameter plays a significant role on the magnitude of the SSI effects, while the pile length has almost no influence. On the other hand, the results highlight the importance of a good knowledge of the soil profile, as high differences are produced between the homogeneous and variable-with-depth profiles, even when both present the same mean shear velocity. The superficial soil layers are found to be the ones of crucial importance when evaluating the SSI effects on the dynamic properties of OWT systems.

show abstract

Integrated FEM and CFD Simulation for Offshore Wind Turbine Structural Response

et al. 2019

View full text Add to dashboard Cite

Strength, stiffness, resonance and the design of offshore wind turbine monopiles

Cited by 30 publications

References 11 publications

Site-specific variability of load extremes of offshore wind turbines exposed to hurricane risk and breaking waves

Site-specific variability of load extremes of offshore wind turbines exposed to hurricane risk and breaking waves

Dynamic Response of Real Offshore Wind Turbines on Monopiles in Stratified Seabed

Integrated FEM and CFD Simulation for Offshore Wind Turbine Structural Response

Contact Info

Product

Resources

About