Lateral Response of Monopiles in Sand under Monotonic and Cyclic Loads

A 3D Finite Element Investigation

Master Thesis (2023)
Author(s)

F. Firman Habib (TU Delft - Civil Engineering & Geosciences)

Contributor(s)

Federico Pisano – Mentor (TU Delft - Geo-engineering)

Luca Flessati – Graduation committee member (TU Delft - Geo-engineering)

Evangelos Kementzetzidis – Graduation committee member (TU Delft - Offshore Engineering)

Haoyuan Liu – Graduation committee member (Norwegian Geotechnical Institute)

Kuen-Wei (Wayne) Wu – Graduation committee member (Van Oord Offshore B.V.)

Naoual El Kanfoudi – Graduation committee member (Van Oord Offshore B.V.)

Faculty
Civil Engineering & Geosciences
Copyright
© 2023 F Firman Habib
More Info
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Publication Year
2023
Language
English
Copyright
© 2023 F Firman Habib
Graduation Date
29-09-2023
Awarding Institution
Delft University of Technology
Programme
Geo-Engineering
Faculty
Civil Engineering & Geosciences
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Abstract

Large-diameter monopiles serve as foundations for offshore wind turbines (OWT), and the diameters are now up to 10 meters. These monopiles exhibit lower embedded length-to-diameter (L/D) ratios compared to the conventional monopile that is widely employed in offshore oil and gas platforms. They undergo rotation when subjected to lateral loading like rigid or semi-rigid bodies. This distinct geometry necessitates a different approach to describe the soil reaction that is induced when a lateral load is applied. Previous research introduced a 1D model incorporating four soil spring components to represent four aspects of soil reaction namely lateral soil reaction, distributed moment, base shear force, and base moment. However, questions have arisen regarding the contributions of base components, specifically the base shear force and base moment, to maintaining monopile stability. In response, a series of monotonic loading tests on monopiles in dry sand is conducted to assess the contributions of base shear force and base moment to monopile stability. Following this assessment of base components, parametric analyses are carried out to investigate the effect of pile diameter (D), the L/D ratio, load eccentricity (e), and sand relative density on monopile responses under cyclic and monotonic lateral loading. In this study, the SANISAND-MS material model is employed within 3D Finite Element (FE) software to model ratcheting during cyclic lateral loading. Finally, an investigation is conducted with the aim of constructing a 0D model to represent base shear force and base displacement responses under both monotonic and cyclic lateral loading.

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