Abstract
Abstract Extending the use of the p–y curves included in the regulation codes API and DNV to design large-diameter monopiles supporting offshore wind turbines (OWTs) was unsuccessful as it resulted in an inaccurate estimation of the monopile behavior. This had prompted many investigators to propose formulations to enhance the performances of Winkler model. In this paper, two case studies are considered. A case consisting of an OWT at Horns Rev (Denmark) supported by a monopile in a sandy soil was studied first. Taking the FEA using ABAQUS as reference, results of WILDOWER 1.0 (a Winkler computer code) using the recently proposed p–y curves giving design parameters were plotted and evaluated. In order to see the ability of proposed p–y curves to predict the monopile head movements, and consequently the first natural frequency (1st NF), a second case study consisting of a monopile supporting an OWT at North Hoyle (UK) was selected. The monopile head stiffness in terms of lateral, rocking, and cross-coupling stiffness coefficients, necessary for the 1st NF, were computed using both ABAQUS and WILDPOWER 1.0. Comparisons with the measured 1st NF showed that with the exception of one p–y model, none of other proposed Winkler methods is able to predict accurately this parameter.
Highlights
Complicated environmental issues combined with the growing harm of the greenhouse gas emission placed the environmentalists in a challenging situation all over the world
It is well recognized that the Winkler model that uses the nonlinear p–y curves proposed by the standards, currently in use [4,5] for monopile design, has gained broad confidence over many decades
The Winkler model using both Sorensen (2012) and Wiemann et al (2004) p–y curves reveals an underestimation of pile displacements along the entire monopile length, showing a deformation pattern close to that exhibited by the API method
Summary
Complicated environmental issues combined with the growing harm of the greenhouse gas emission placed the environmentalists in a challenging situation all over the world. It is well recognized that the Winkler model that uses the nonlinear p–y curves proposed by the standards, currently in use [4,5] for monopile design, has gained broad confidence over many decades As this model has been developed on the basis of field testing investigations performed on small-diameter piles (Dp=0.61 m) with an (Lp ⁄Dp) ratio of 34.0 [6,7], it does not appear capable of reasonably predicting the lateral response of large-diameter monopiles supporting OWTs. For an. The main objective of this paper is to assess the performances of the currently used p–y models (API and DNV) and the enhanced p–y curves recently proposed to design monopiles under lateral loading This is achieved by a comparative study between the results supplied by a computer program called WILDPOWER 1.0 [8] and those of the Finite Element (FE) analysis obtained using the commercial package ABAQUS. Since the soil in contact with the monopile is much softer than the monopile, it was selected as the slave surface and the monopile was selected as the master surface
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