Monopile foundations are frequently used for offshore wind energy converters. These piles are highly laterally loaded structures with large horizontal forces and bending moments. Due to the harsh environmental conditions in the southern North Sea diameters of 4 to 8 m are required to maintain serviceability. In common practice smaller laterally loaded pipe piles are designed using the well-known p-y-method, in which the pile-soil stiffness is considered by nonlinear p-y-curves derived from field tests. An alternative design method is the strain wedge method in which the pile response is derived from the stress-strain relationship of the soil assuming a certain failure zone ahead of the pile. In the present paper, the design of a large diameter monopile foundation for typical loading conditions is presented. The pile response in cohesionless soil determined by the p-y method and the strain wedge method is compared with a finite element (FE) analysis with respect to scale effects when extrapolated from commonly used pipe pile diameters to large size monopiles.
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