0
Research Papers: Offshore Geotechnics

Effects of Soil Profile Variation and Scour on Structural Response of an Offshore Monopile Wind Turbine

[+] Author and Article Information
Hui Li

College of Shipbuilding Engineering,
Harbin Engineering University,
Harbin 150001, China
e-mail: huili@hrbeu.edu.cn

Muk Chen Ong

Department of Mechanical and Structural
Engineering and Materials Science,
University of Stavanger,
Stavanger 4036, Norway
e-mail: muk.c.ong@uis.no

Bernt Johan Leira

Department of Marine Technology,
Norwegian University of Science
and Technology,
Trondheim 7491, Norway
e-mail: bernt.leira@ntnu.no

Dag Myrhaug

Department of Marine Technology,
Norwegian University of Science
and Technology,
Trondheim 7491, Norway
e-mail: dag.myrhaug@ntnu.no

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received August 23, 2016; final manuscript received February 7, 2018; published online March 14, 2018. Assoc. Editor: Lizhong Wang.

J. Offshore Mech. Arct. Eng 140(4), 042001 (Mar 14, 2018) (10 pages) Paper No: OMAE-16-1099; doi: 10.1115/1.4039297 History: Received August 23, 2016; Revised February 07, 2018

This paper presents an engineering approach to study the effects of soil profile variation and scour on structural response of an offshore monopile wind turbine. A wind-wave model for finite water depth is proposed to obtain the corresponding sea-state based on the incident wind. Different wind, wave, and current loads on the wind turbine for the operational conditions are considered. The interaction between the foundation and the soil is simulated by nonlinear springs, for which stiffness properties are obtained from the axial load transfer curve, the tip load–displacement curve, and the lateral load–deflection curve. Four types of soil conditions are considered, i.e., 100% sand layer, 50% sand layer (top) and 50% clay layer (bottom), 50% clay layer (top), and 50% sand layer (bottom), as well as 100% clay layer. For a given current speed, the variations of the structural response of the wind turbine due to the effects of different wind–wave load combinations, soil conditions and scour have been investigated. Different wind–wave load combinations directly affect the mean internal bending moment and mean displacement vertically along the support structure. Different soil conditions change the eigenfrequency of the structure significantly. The top layer of the soil appears to have a strong influence on the mean internal bending moment and the mean shear force distribution along the foundation. Moreover, the effect of scour alters the eigenfrequency of the structure significantly. The maximum mean bending moment and displacement increase for the cases with a scour hole as compared to the cases with scour protection.

Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.

References

Van Der Tempel, J. , 2006, “ Design of Support Structures for Offshore Wind Turbines,” Ph.D. thesis, TU Delft, Delft, The Netherlands. https://repository.tudelft.nl/islandora/object/uuid%3Aae69666e-3190-4b22-84ed-2ed44c23e670
Kellezi, L. , and Hansen, P. B. , 2003, “ Static and Dynamic Analysis of an Offshore Mono-Pile Windmill Foundation,” BGA International Conference on Foundations: Innovations, Observations, Design and Practice (ICOF2003), Dundee, Scotland, Sept. 2–5, pp. 401–410. https://vulcanhammerinfo.files.wordpress.com/2017/08/kellezi-hansen.pdf
Yang, Z. , and Jeremic, B. , 2002, “ Numerical Analysis of Pile Behavior Under Lateral Loads in Layered Elastic-Plastic Soil,” Int. J. Numer. Anal. Methods Geomech., 26(14), pp. 1385–1406.
El Naggar, M. H. , and Bentley, K. J. , 2000, “ Dynamic Analysis for Laterally Loaded Piles and Dynamic p–y Curves,” Can. Geotech. J., 37(6), pp. 1166–1183. [CrossRef]
Sen, R. , Davis, T. G. , and Banerjee, P. K. , 1985, “ Dynamic Analysis of Piles and Pile Groups Embedded in Homogeneous Soil,” Int. J. Earthquake Eng. Struct. Dyn., 13(1), pp. 53–65. [CrossRef]
Zaaijer, M. B. , 2008, “ Foundation Modeling to Assess Dynamic Behavior of Offshore Wind Turbines,” Appl. Ocean Res., 28(1), pp. 45–57. [CrossRef]
Van Buren, E. , 2011, “ Effect of Foundation Modeling Methodology on the Dynamic Response of Offshore Wind Turbine Support Structures,” ASME Paper No. OMAE2011-49492.
API, 1993, “ Recommended Practices of Planning Designing and Constructing Fixed Offshore Platform-Load and Resistance Factor Design,” American Petroleum Institute, Washington, DC, Standard No. API-RP2A-LRFD. https://standards.globalspec.com/std/231832/api-rp-2a-lrfd
Matlock, H. , 1970, “ Correlations for Design of Laterally Loaded Piles in Clay,” Offshore Technology Conference, Houston, TX, Apr. 22--24, Paper No. OTC-1204-MS.
Stevens, J. B. , and Audibert, J. M. E. , 1979, “ Re-Examination of P-Y Curve Formulations,” Offshore Technology Conference, Houston, TX, Apr. 30–May 3, Paper No. OTC-3402-MS.
Jeanjean, P. , 2009, “ Re-Assessment of P-Y Curves for Soft Clays From Centrifuge Testing and Finite Element Modelling,” Offshore Technology Conference, Houston, TX, May 4–7, Paper No. OTC-20158-MS.
Hamilton, J. M. , and Murff, J. D. , 1995, “ Ultimate Lateral Capacity of Piles in Clay,” Offshore Technology Conference, Houston, TX, May 1–4, Paper No. OTC-7667-MS.
Doyle, E. H. , Dean, E. T. R. , Sharma, J. S. , Bolton, M. D. , Valsangkar, A. J. , and Newlin, J. A. , 2004, “ Centrifuge Model Tests on Anchor Piles for Tension Leg Platforms,” Offshore Technology Conference, Houston, TX, May 3–6, Paper No. OTC-16845-MS.
Zhang, C. , White, D. , and Randolph, M. , 2011, “ Centrifuge Modeling of the Cyclic Lateral Response of a Rigid Pile in Soft Clay,” J. Geotech. Geoenviron. Eng., 137(7), pp. 717–729. [CrossRef]
Hong, Y. , He, B. , Wang, L. Z. , Wang, Z. , Ng, C. W. W. , and Masin, D. , 2017, “ Cyclic Lateral Response and Failure Mechanisms of a Semi-Rigid Pile in Soft Clay: Centrifuge Tests and Numerical Modelling,” Can. Geotech. J., 54(6), pp. 806–824. [CrossRef]
Hansen, A. C. , and Butterfield, C. P. , 1993, “ Aerodynamics of Horizontal-Axis Wind Turbines,” Annu. Rev. Fluid Mech., 25(1), pp. 115–149. [CrossRef]
Benini, E. , and Toffolo, A. , 2002, “ Optimal Design of Horizontal-Axis Wind Turbines Using Blade-Element Theory and Evolutionary Computation,” ASME J. Sol. Energy Eng., 124(4), pp. 357–363. [CrossRef]
Myrhaug, D. , Ong, M. C. , Føien, H. , Gjengedal, C. , and Leira, B. J. , 2009, “ Scour Below Pipelines and Around Vertical Piles Due to Second-Order Random Waves Plus a Current,” Ocean Eng., 36(8), pp. 605–616. [CrossRef]
Ong, M. C. , Myrhaug, D. , and Hesten, P. , 2013, “ Scour Around Vertical Piles Due to Long-Crested and Short-Crested Nonlinear Random Waves Plus a Current,” Coastal Eng., 73, pp. 106–114. [CrossRef]
Gao, Z. , Saha, N. , Moan, T. , and Amdahl, J. , 2010, “ Dynamic Analysis of Offshore Fixed Wind Turbines Under Wind and Wave Loads Using Alternative Computer Codes,” Third EAWE Conference, TORQUE 2010: The Science of Making Torque From Wind, Crete, Greece.
Jonkman, J. M. , and Musial, W. , 2010, “ Offshore Code Comparison Collaboration (OC3) for IEA Task 23 Offshore Wind Technology and Deployment,” National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/TP-5000-48191. https://www.nrel.gov/docs/fy11osti/48191.pdf
Jonkman, J. M. , Butterfield, S. , Musial, W. , and Scott, G. , 2009, “ Definition of a 5-MW Reference Wind Turbine for Offshore System Development,” National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/TP-500-38060. https://www.nrel.gov/docs/fy09osti/38060.pdf
IEC, 2005, “ Wind Turbines—Part1: Design Requirements,” IEC International, International Electrotechnical Commission, Geneva, Switzerland, Standard No. IEC 614000-1. https://webstore.iec.ch/preview/info_iec61400-1%7Bed3.0%7Den.pdf
IEC, 2009, “ Wind Turbines—Part3: Design Requirements of Offshore Wind Turbines,” International Electrotechnical Commission, Geneva, Switzerland, Standard No. IEC 614000-3. https://webstore.iec.ch/publication/5446
Jonkman, J. M. , and Buhl, M. L. J. , 2005, “ FAST User's Guide,” National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/EL-500-38230. http://wind.nrel.gov/public/bjonkman/TestPage/FAST.pdf
Wheeler, J. D. , 1970, “ Method for Calculating Forces Produced by Irregular Waves,” J. Pet. Technol., 22(3), pp. 359–367. [CrossRef]
Holthuijsen, L. H. , 2007, Waves in Oceanic and Coastal Waters, Taylor and Francis Ltd., Cambridge, UK, Chap. 8. [CrossRef]
Jensen, J. J. , 2002, “ Conditional Short-Crested Waves in Shallow Water and With Superimposed Current,” ASME Paper No. OMAE2002-28399.
Sumer, B. M. , and Fredsøe, J. , 2002, The Mechanics of Scour in the Marine Environment, World Scientific, Singapore, Chap. 3. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

An overview of the dynamic analysis procedure for bottom-fixed monopile offshore wind turbine

Grahic Jump Location
Fig. 2

NREL 5 MW monopile offshore wind turbine, three blades, with all dimensions in meter

Grahic Jump Location
Fig. 3

Coordinate system for the wind load

Grahic Jump Location
Fig. 4

Mean wind force in the x-direction at the tower-top versus the mean wind speed at the hub height

Grahic Jump Location
Fig. 5

Standard deviation of the wind force in the x-direction at the tower-top versus the mean wind speed at the hub height

Grahic Jump Location
Fig. 6

Distributed nonlinear springs based on tz curve, Qz curve, and py curve

Grahic Jump Location
Fig. 7

Scour hole around a vertical pile

Grahic Jump Location
Fig. 8

A typical loading setup in the abaqus-FEM model for the cases without and with a scour hole

Grahic Jump Location
Fig. 9

Mean internal bending moment about the y-axis versus the vertical position along the wind turbine for (a) sand1–sand4 and (b) clay1–clay4

Grahic Jump Location
Fig. 10

Mean displacement in the x-direction versus the vertical position along the wind turbine for (a) sand1–sand4 and (b) clay1–clay4

Grahic Jump Location
Fig. 11

Mean displacements in the x-direction versus the vertical position along the wind turbine for sand2, sand-clay2, clay-sand2, and clay2

Grahic Jump Location
Fig. 12

Mean internal bending moment about the y-axis versus the vertical position along the wind turbine for sand2, sand-clay2, clay-sand2, and clay2

Grahic Jump Location
Fig. 13

Mean sectional shear force in the x-direction versus the vertical position along the wind turbine for sand2, sand-clay2, and clay2

Grahic Jump Location
Fig. 14

Mean displacements in the x-direction versus the vertical position along the wind turbine for (a) sand2 versus sandscour2 and (b) sand-clay2 versus sand-clayscour2

Grahic Jump Location
Fig. 15

Mean internal bending moment about the y-axis versus the vertical position along the wind turbine for (a) sand2 versus sandscour2 and (b) sand-clay2 and sand-clayscour2

Grahic Jump Location
Fig. 16

Mean internal bending moment about the y-axis versus the vertical position along the wind turbine for sandscour2 versus sand-clayscour2

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In