Horizontal Static Impedances for OWT Monopiles Based on Timoshenko Beam Theory
Publication: International Journal of Geomechanics
Volume 23, Issue 11
Abstract
Euler beam theory is always used for soil–pile analysis; however, its use is questionable for laterally loaded large-diameter monopiles. In this paper, the solution on the static impedances of monopiles under a combination of axial and horizontal loads was proposed based on three-dimensional continuous medium theory and Timoshenko beam theory. From the analysis results, the use of the Euler–Bernoulli beam theory leads to larger pile-head impedances, and the feature is more significant with lower aspect ratios and stronger pile-bottom constraints. The difference in the impedance from two theories may be up to 10%–43%. Consequently, Timoshenko beam theory is more appropriate for large-diameter monopiles, especially for monopiles with strong bottom constraints (such as rock-socketed monopiles). Meanwhile, the shear force and bending moment at the pile bottom have a considerable effect on the static impedances of large-diameter short monopiles, and only a consideration of the impedance contribution from the soil around the pile is insufficient. Furthermore, both the deflection and the bending moment of the pile increase due to the second-order effect of axial force, but the effect of the axial force on the impedance can be neglected for practical monopile designs. A simple and efficient approach to evaluate the impedance of large-diameter monopiles is desirable for designers, thus a simplified empirical equation for the pile-head static impedance was proposed for ease in calculating each component of static impedances for the large-diameter monopiles of offshore wind turbines (OWTs).
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Acknowledgments
This work is supported by the National Natural Science Foundation of China (Grant Nos. 52178312, 52008059, and 52178318), the Innovation Group Science Foundation of the Natural Science Foundation of Chongqing, China (Grant No. cstc2020jcyj-cxttX0003), the Open Research Fund Program of Guangdong Key Laboratory of Earthquake Engineering and Application Technology (Grant No. 2020B1212060071), and the Science & Technology Project of the Education Department of Jiangxi Province (Grant No. GJJ2200681). The corresponding author would like to acknowledge the China Scholarship Council for the support for his study at the National University of Singapore.
Author contributions: Guangwei Cao: Conceptualization, Methodology, Data curation, Formal analysis, Programming, Writing-original draft, Visualization. Siau Chen Chian: Resources, Software, Writing-review & editing, Supervision. Xuanming Ding: Conceptualization, Writing—review & editing, Funding acquisition, Supervision. Lubao Luan: Funding acquisition, Supervision, Writing—review & editing, Software. Changjie Zheng: Funding acquisition, Supervision, Writing—review & editing. Peng Zhou: Funding acquisition, Writing—review & editing.
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Published In
International Journal of Geomechanics
Volume 23 • Issue 11 • November 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Sep 26, 2022
Accepted: May 21, 2023
Published online: Sep 4, 2023
Published in print: Nov 1, 2023
Discussion open until: Feb 4, 2024
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