A Comparative Study between Three-Legged and Tripod Sub-structures in Design of Offshore Wind Turbines in the Transition Water Depth


  • Aliakbar Khosravi
  • Tuck Wai Yeong
  • Mohammed Parvez Anwar
  • Jayaprakash Jaganathana
  • Teck Leong Lau
  • Wael Elleithy






Installation method, substructure, three-legged, tripod, wind turbines.


This research aimed at investigating tripod and three-legged offshore wind turbine substructures. A comparison between the two substructures based on their weight as well as the installation method of piles, i.e. pre-piling and post-piling, was carried out. The in-place (Ultimate Limit State), Dynamic, natural frequency check and fatigue (Fatigue Limit State) analyses were conducted considering aerodynamic and hydrodynamic loads imposed on substructures in 50m water depth. An optimisation process was carried out in order to reduce the mass of substructures. The results revealed that the three-legged substructure is more cost effective with 25% lesser structure mass. However, the construction of the three-legged structure usually takes more time due to increased number of members and subsequently welding joints. The results, furthermore, showed that the pre-piling method reduces the time and cost of offshore installation, and reduces the weight of piles by 50%.




[1] Arany L, Bhattacharya S, Macdonald J & Hogan SJ, “Design of monopiles for offshore wind turbines in 10 stepsâ€, Soil Dynamics and Earthquake Engineering, Vol. 92, 2017, pp. 126-152.

[2] Kaveh A & Sabeti S, “Optimal Design of Jacket Supporting Structures for Offshore Wind Turbines Using CBO and ECBO Algorithmsâ€, Periodica Polytechnica Civil Engineering, Vol. 62, No. 3, 2018, 10 pp.

[3] Ma L & Nishino T, “Preliminary estimate of the impact of support structures on the aerodynamic performance of very large wind farmsâ€, Journal of Physics: IOP Conf. Series 1037, 2018, 15 pp., doi :10.1088/1742-6596/1037/7/072036

[4] Damiani R, Dykes K & Scott G, “A comparison study of offshore wind support structures with monopiles and jackets for U.S. watersâ€, Journal of Physics: IOP Conf. Series 753, 2016, 14 pp., doi:10.1088/1742-6596/753/9/092003

[5] Jonkman JM (2007), Dynamics Modeling and Loads Analysis of an Offshore Floating Wind Turbine, Technical Report NREL/TP-500-41958, NREL National Renewable Energy Laboratory.

[6] Kolios A, Collu M, Chahardehi, A, Brennan FP & Patel MH, “A Multi-Criteria Decision Making Method to Compare Support Structures for Offshore Wind Turbinesâ€, EWEC2010, Europe’s premier wind energy event, Warsaw, 2010, 9 pp.

[7] Ashish CB & Panneer Selvam R, “Static and Dynamic Analysis of Jacket Substructure for Offshore Fixed Wind Turbinesâ€, the Eighth Asia-Pacific Conference on Wind Engineering,, Chennai, India, 2013, pp. 1294-1302.

[8] Chew KH, Ng EYK, Tai K, Muskulus, K & Zwick D, “A Comparison Study Between Four-Legged and Three-Legged Designsâ€, Journal of Ocean and Wind Energy, The International Society of Offshore and Polar Engineers, Vol. 1 No. 2, 2014, pp. 74–81.

[9] Vitor (2016). Reshadat Oil Field Redevelopment, Persian Gulf, Iran, available at http://www.offshore-technology.com/projects/reshadat-oil-fieldredevelopment-persian-gulf/reshadat-oil-field-redevelopment-persian-gulf1.html

[10] de Vries, W. (2011). Final Report WP 4.2: Support Structure Concepts for Deep Water, Technical Report UpWind Deliverable D4.2.8, Delft University of Technology, Delft, Netherlands, 210 pp.

[11] Bhattacharya S, “Challenges in Design of Foundations for Offshore wind turbinesâ€, Engineering & Technology Reference, The institution of engineering and technology, 2014, pp. 1-9.

[12] Brebbia CA & Walker S (1979), Dynamic Analysis of Offshore Structures, Butterworths.

[13] Khalifa AA, Aboul Haggag SY & Fayed, MN, “Fatigue Assessment Analysis of Offshore Structures with Application to an Existing Platform in Suez Gulf, Egyptâ€, World Applied Sciences Journal, Vol. 30 No, 8, 2014, pp. 1000-1019.

[14] Noorzaei J, Bahrom SI, Jaafar MS, Thanoon1 WAM & Mohammad S, “Simulation of Wave and Current Forces on Template Offshore Structuresâ€, Suranaree Journal of Science and Technology, Vol. 12 Issue 3, 2005, pp. 193-210.

[15] Henderson R. & Camp TR, “Hydrodynamic Loading of Offshore Wind Turbinesâ€, European Wind Energy Conference European conference, Wind Energy; Wind energy for the new millennium; Copenhagen, 2001, pp. 561-566.

[16] Chakrabarti SK (2005), Handbook of Offshore Engineering, Elsevier.

[17] Zaaijer, MB, “Comparison of Monopile, Tripod, Suction Bucket and Gravity Base Design for a 6 Mw Turbineâ€, Offshore Wind energy in Mediterranean and Other European Seas, OWEMES, Naples, Italy, 2003.

[18] Abdel Raheem SE, “Nonlinear Response of Fixed Jacket Offshore Platform under Structural and Wave Loadsâ€, Coupled Systems Mechanics, Vol. 2 No. 1,2013, pp. 111-126.

[19] Efthymiou, M. and Durkin, S. (1985), “Stress concentration in T/Y and gap/overlap K-jointsâ€, in Behaviour of Offshore Structures, Elsevier Science Publishers B.V., Amsterdam, The Netherlands, pp. 429–440.

[20] Bentley SACS Version 5.7 (2013), EDI, Soft-ware Manual Version 7.

[21] API 2A - LRFD Reaffirmed (2003), Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms-Load and Resistance Factor Design, American Petroleum Institute.

[22] API RP 2A - WSD 21st Edition (2000), Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Working Stress Design, American Petroleum Institute

[23] DNV (2011), Fatigue Design of Offshore Steel Structures, Recommended Practice DNV-RP-C203, Det Norske Veritas AS, 176 pp.

[24] DNV (2014). Design of Offshore Wind Turbine Structures, Offshore Standard DNV-OS-J101, DET Norske Veritas AS, 238 pp.

[25] ISO (2007), Petroleum and natural gas industries - Fixed steel offshore structures, ISO 19902, International Organization for Standardization.

View Full Article:

How to Cite

Khosravi, A., Wai Yeong, T., Parvez Anwar, M., Jaganathana, J., Leong Lau, T., & Elleithy, W. (2018). A Comparative Study between Three-Legged and Tripod Sub-structures in Design of Offshore Wind Turbines in the Transition Water Depth. International Journal of Engineering & Technology, 7(3.36), 23–33. https://doi.org/10.14419/ijet.v7i3.36.29073
Received 2019-04-30
Accepted 2019-04-30
Published 2018-05-06