Response of Long-term Cyclic Laterally Loaded Monopiles in Sand
Downloads
The offshore wind energy industry has grown rapidly, with large-diameter monopiles becoming the primary foundation choice for offshore turbines. Monopile designs emphasize serviceability and fatigue limits, enforcing strict rotation limits set by manufacturers. These structures face considerable lateral cyclic loads from waves, currents, and wind. Existing design codes such as API and DNV GL are commonly used but do not sufficiently capture monopile behavior under cyclic loading, particularly regarding load cycle count, amplitude, and type. Moreover, the dynamic response of the monopile-soil system, which affects the foundation’s natural frequency, depends on the pile-soil interaction stiffness—an aspect neglected in current standards. This research reports results from seventeen 1-g cyclic loading experiments and six monotonic tests on monopiles installed in dry sand. Findings reveal that cyclic deformation is significantly influenced by sand relative density, load cycle number, and cyclic load characteristics (magnitude and type). Cyclic loading also alters the pile-soil stiffness. Accumulated rotation grows exponentially with increasing load cycles, while cyclic secant stiffness increases logarithmically. The study further identifies asymmetric two-way cyclic loading as the most damaging load pattern for monopile performance.
Downloads
[1] GWEC. (2023). Global Wind Report 2023. Global Wind Energy Council (GWEC), Lisbon, Portugal.
[2] Li, J., Wang, G., Li, Z., Yang, S., Chong, W. T., & Xiang, X. (2020). A review on development of offshore wind energy conversion system. International Journal of Energy Research, 44(12), 9283–9297. doi:10.1002/er.5751.
[3] Rathod, D., Krishnanunni, K. T., & Nigitha, D. (2020). A Review on Conventional and Innovative Pile System for Offshore Wind Turbines. Geotechnical and Geological Engineering, 38(4), 3385–3402. doi:10.1007/s10706-020-01254-0.
[4] Li, D., Zhao, J., Wu, Y., Zhang, Y., & Liang, H. (2024). An innovative bionic offshore wind foundation: Scaled suction caisson. Renewable and Sustainable Energy Reviews, 191, 114208. doi:10.1016/j.rser.2023.114208.
[5] Wang, Y., Zhu, M., Dai, G., Xu, J., & Wu, J. (2024). Analytical framework for natural frequency shift of monopile-based wind turbines under two-way cyclic loads in sand. Geomechanics and Engineering, 37(2), 167–178. doi:10.12989/gae.2024.37.2.167.
[6] Murchison, J. M., & O’Neill, M. (1983). An evaluation of p-y relationships in sands. Master's thesis, Dept. of Civil Engineering, Cullen College of Engineering. University of Houston-University Park, Dallas, United States.
[7] LeBlanc, C., Houlsby, G. T., & Byrne, B. W. (2010). Response of stiff piles in sand to long-term cyclic lateral loading. Geotechnique, 60(2), 79–90. doi:10.1680/geot.7.00196.
[8] Reese, L. C., Cox, W. R., & Koop, F. D. (1974). Analysis of Laterally Loaded Piles in Sand. Offshore Technology Conference. doi:10.4043/2080-ms.
[9] API RP 2A-WSD 22nd Ed. (2014). Planning, Designing, and Constructing Fixed Offshore Platforms - Working Stress Design. American Petroleum Institute (API), Wahington, United States.
[10] DNVGL-ST-0126. (2018). Support structures for wind turbines. Det Norske Veritas (DNV), Bærum, Norway
[11] Briaud, J. L., Smith, T. O., & Meyer, B. J. (1983). Using the Pressuremeter Curve to Design Laterally Loaded Piles. Offshore Technology Conference. doi:10.4043/4501-ms.
[12] Poulos, H. G., & Hull, T. S. (1989). The role of analytical geomechanics in foundation engineering. Foundation engineering: Current principles and practices. American Society of Civil Engineers (ASCE), Reston, United States.
[13] Abdel-Rahman, K., & Achmus, M. (2005). Finite element modelling of horizontally loaded monopile foundations for offshore wind energy converters in Germany. International Symposium on Frontiers in Offshore Geotechnics (ISFOG), Perth, Australia. doi:10.1201/noe0415390637.ch38.
[14] Davidson, H. L. (1981). Laterally loaded drilled pier research. Electric Power Research Institute (EPRI), Palo Alto, United States.
[15] Gerolymos, N., & Gazetas, G. (2006). Development of Winkler model for static and dynamic response of caisson foundations with soil and interface nonlinearities. Soil Dynamics and Earthquake Engineering, 26(5), 363–376. doi:10.1016/j.soildyn.2005.12.002.
[16] Lam, I. P., & Martin, G. R. (1986). Seismic design for highway bridge foundations. Report No. FHWA/RD-86/102, FHWA, McLean, United States.
[17] Byrne, B., McAdam, R., Burd, H., Houlsby, G., Martin, C., c, L., Taborda, D., Potts, D., Jardine, R., Sideri, M., Schroeder, F., Gavin, K., Doherty, P., Igoe, D., Wood, A., Kallehave, D., & Gretlund, J. (2015). New design methods for large diameter piles under lateral loading for offshore wind applications. Frontiers in Offshore Geotechnics III, 705–710. doi:10.1201/b18442-96.
[18] Little, R. L., & Briaud, J. L. (1988). Full scale cyclic lateral load tests on six single piles in sand. Miscellaneous Paper GL-88-27. Geotechnical Division, Texas A&M University, Texas, United States.
[19] Akdag, C. T., & Rackwitz, F. (2024). Long-term horizontal cyclic loading model test results of monopile for offshore wind turbines. Geotechnical Engineering Challenges to Meet Current and Emerging Needs of Society, 2755–2759. doi:10.1201/9781003431749-536.
[20] Ma, J., Xu, J., Fan, Z., Li, H., & Xu, G. (2024). Bearing and deformation characteristics of monopile foundation under monotonic and cyclic horizontal loads. Science Progress, 107(2), 00368504241260268. doi:10.1177/00368504241260268.
[21] Wang, Y., Dai, G., Li, H., Gao, L., & Li, B. (2025). Lateral response of monopiles under cyclic loading in sand: Laboratory model tests and theoretical studies. Ocean Engineering, 322(October), 120500. doi:10.1016/j.oceaneng.2025.120500.
[22] Peralta, P. (2010). Investigations on the behavior of large diameter piles under long-term lateral cyclic loading in cohesionless soil. PhD Thesis, Leibniz University, Hannover, Germany
[23] Klinkvort, R. T., & Hededal, O. (2013). Lateral response of monopile supporting an offshore wind turbine. Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 166(2), 147–158. doi:10.1680/geng.12.00033.
[24] Nicolai, G., & Ibsen, L. B. (2014). Small-scale testing of cyclic laterally loaded monopiles in dense saturated sand. International Ocean and Polar Engineering Conference, 15-20 June, 2014, Busan, Korea.
[25] Li, W., Igoe, D., & Gavin, K. (2015). Field tests to investigate the cyclic response of monopiles in sand. Proceedings of the Institution of Civil Engineers: Geotechnical Engineering, 168(5), 407–421. doi:10.1680/jgeen.14.00104.
[26] Arshad, M., & O’Kelly, B. C. (2017). Model Studies on Monopile Behavior under Long-Term Repeated Lateral Loading. International Journal of Geomechanics, 17(1), 1–12. doi:10.1061/(asce)gm.1943-5622.0000679.
[27] Albiker, J., Achmus, M., Frick, D., & Flindt, F. (2017). 1 G Model Tests on the Displacement Accumulation of Large-Diameter Piles Under Cyclic Lateral Loading. Geotechnical Testing Journal, 40(2), 173–184. doi:10.1520/GTJ20160102.
[28] Truong, P., Lehane, B. M., Zania, V., & Klinkvort, R. T. (2019). Empirical approach based on centrifuge testing for cyclic deformations of laterally loaded piles in sand. Geotechnique, 69(2), 133–145. doi:10.1680/jgeot.17.P.203.
[29] Li, Q., Askarinejad, A., & Gavin, K. (2022). Lateral response of rigid monopiles subjected to cyclic loading: centrifuge modelling. Proceedings of the Institution of Civil Engineers: Geotechnical Engineering, 175(4), 426–438. doi:10.1680/jgeen.20.00088.
[30] Richards, I. A., Byrne, B. W., & Houlsby, G. T. (2020). Monopile rotation under complex cyclic lateral loading in sand. Geotechnique, 70(10), 916–930. doi:10.1680/jgeot.18.P.302.
[31] Frick, D., & Achmus, M. (2022). A model test study on the parameters affecting the cyclic lateral response of monopile foundations for offshore wind turbines embedded in non-cohesive soils. Wind Energy Science, 7(4), 1399–1419. doi:10.5194/wes-7-1399-2022.
[32] Rovere, M. (2004). Cyclic loading test machine for caisson suction foundations. Ecole Centrale de Lille/Politecnico di Milano, Milan, Italy.
[33] Abadie, C. (2015). Cyclic lateral loading of monopile foundations in cohesionless soils. Ph.D. Thesis, University of Oxford, Oxford, United Kingdom.
[34] Bolton, M. D. (1986). The strength and dilatancy of sands. Geotechnique, 36(1), 65–78. doi:10.1680/geot.1986.36.1.65.
[35] Garnier, J., Gaudin, C., Springman, S. M., Culligan, P. J., Goodings, D., Konig, D., Kutter, B., Phillips, R., Randolph, M. F., & Thorel, L. (2007). Catalogue of scaling laws and similitude questions in geotechnical centrifuge modelling. International Journal of Physical Modelling in Geotechnics, 7(3), 01–23. doi:10.1680/ijpmg.2007.070301.
[36] Manoliu, G., I1, D., V, D., Radulescu, N., & Dobrescu. (1984). International society for soil mechanics and foundation engineering. Geotextiles and Geomembranes, 1(2), 161–162. doi:10.1016/0266-1144(84)90012-8.
[37] Lee, J., Paik, K., Kim, D., & Park, D. (2012). Estimation of ultimate lateral load capacity of piles in sands using calibration chamber tests. Geotechnical Testing Journal, 35(4), 103756. doi:10.1520/GTJ103756.
[38] Frick, D., & Achmus, M. (2020). An experimental study on the parameters affecting the cyclic lateral response of monopiles for offshore wind turbines in sand. Soils and Foundations, 60(6), 1570–1587. doi:10.1016/j.sandf.2020.10.004.
[39] Jalbi, S., Arany, L., Salem, A. R., Cui, L., & Bhattacharya, S. (2019). A method to predict the cyclic loading profiles (one-way or two-way) for monopile supported offshore wind turbines. Marine Structures, 63, 65–83. doi:10.1016/j.marstruc.2018.09.002.
- Authors retain all copyrights. It is noticeable that authors will not be forced to sign any copyright transfer agreements.
- This work (including HTML and PDF Files) is licensed under a Creative Commons Attribution 4.0 International License.
