Augustesen, Anders Hust

Brødbæk, K. T.

Ibsen, Lars Bo

Møller, M.

Sørensen, Søren Peder Hyldal

English

Monopiles are an often used foundation concept for offshore wind turbine converters. These piles are highly subjected to lateral loads and thereby bending moments due to wind and wave forces. To ensure enough stiffness of the foundation and an acceptable pile-head deflection, monopiles with diameters of 4 to 6 m are typically necessary. In current practice these piles are normally designed by use of the p-y curve method although the method is developed and verified for slender piles with diameters up to approximately 2 m. This paper treats numerical models constructed in the commercial programs FLAC3D and Plaxis 3D Foundation with the objective to examine horizontally loaded, large-diameter piles in cohesionless soil. First, the models are calibrated to six small-scale tests conducted in a pressure tank. Hereafter, the models are extended to large-scale simulations. The large-scale simulations are evaluated with the following main findings: Non-slender piles behave almost rigidly when subjected to lateral loads implying a significant deflection at the pile-toe; the initial stiffness of the p-y curves is found to increase for an increase in diameter; the initial stiffness of the p-y curves is independent of the embedded length of the pile and the pile bending stiffness; the initial stiffness of the p-y curves does not vary linearly with depth as suggested in the offshore design regulations; the Winkler model approach is found to provide reasonable results for large-diameter, non-slender piles if the initial stiffness is updated to vary by means of a power function.Monopiles are an often used foundation concept for offshore wind turbine converters. These piles are highly subjected to lateral loads and thereby bending moments due to wind and wave forces. To ensure enough stiffness of the foundation and an acceptable pile-head deflection, monopiles with diameters of 4 to 6 m are typically necessary. In current practice these piles are normally designed by use of the p-y curve method although the method is developed and verified for slender piles with diameters up to approximately 2 m. This paper treats numerical models constructed in the commercial programs FLAC3D and Plaxis 3D Foundation with the objective to examine horizontally loaded, large-diameter piles in cohesionless soil. First, the models are calibrated to six small-scale tests conducted in a pressure tank. Hereafter, the models are extended to large-scale simulations. The large-scale simulations are evaluated with the following main findings: Non-slender piles behave almost rigidly when subjected to lateral loads implying a significant deflection at the pile-toe; the initial stiffness of the p-y curves is found to increase for an increase in diameter; the initial stiffness of the p-y curves is independent of the embedded length of the pile and the pile bending stiffness; the initial stiffness of the p-y curves does not vary linearly with depth as suggested in the offshore design regulations; the Winkler model approach is found to provide reasonable results for large-diameter, non-slender piles if the initial stiffness is updated to vary by means of a power function

Numerical Evaluation of Load-Displacement Relationships for Non-Slender Monopiles in Sand

https://vbn.aau.dk/ws/files/18897478/Numerical_Evaluation_of_Load-Displacement_Relationships_for_Non-Slender_Monopiles_in_Sand

Numerical Evaluation of Load-Displacement Relationships for Non-Slender Monopiles in Sand

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