Scale Effects in Lateral Load Response of Large Diameter Monopiles

Abstract

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.

Seismic Fragility Analysis of Monopile Offshore Wind Turbines under Different Operational Conditions

“…It could be stiff for large diameter piles [46,47]. For this reason, researchers have advised the use of caution when applying p-y curves to large diameter monopile offshore wind turbines [2,48,49]. Nevertheless, p-y curves are the recommended method for lateral soil-pile resistance by the design standard DNVGL-ST-0126 [2], hence they were used herein to study the effect of environmental loads on seismic response of wind turbines.…”

Investigation of nonlinear wave-induced seabed response around mono-pile foundation

“…Hansen (2012) In reality, the ratios of embedment depth for mono-pile foundation of offshore wind turbine and 480 mono-pile diameter often vary from 4 to 8 at shallow/intermediate water depth (Lesny et al, 2007). 481…”

Strength, stiffness, resonance and the design of offshore wind turbine monopiles

“…The toe of the monopile is modeled with a roller support. It is important to note that the P-Y curve method was originally developed for small diameter, flexible piles, and has been shown to be too stiff when applied to large diameter piles such as those considered here [15][16][17]. For this reason, researchers have advised using caution when applying P-Y curves to large diameter OWT monopiles [15]; nevertheless, P-Y curves are the recommended method for modeling lateral soil-pile resistance by the design standard DNV-OS-J101 [18] and they are used here for their simplicity and since this paper is considering flexible mudline conditions that are broadly representative rather than a specific case.…”