Single large diameter piles, known as monopiles, are, nowadays, the most common foundation type for offshore wind turbines (OWT). Several research initiatives have been focusing on improving the conventional design practice. The PISA (Pile Soil Analysis) joint industry research project resulted in a proposal for a new design methodology for OWT pile foundations, focusing on laterally loaded monopiles, with length-to-diameter ratios (L/D) between 2 and 6. The proposed methodology defines a one-dimensional (1D) model, based on the use of Timoshenko beam theory, which overcomes certain limitations in current design practice. Soil reaction components can either be generated through mathematical formulations (rule-based design method) or calibrated from 3D Finite Element (FE) models (numericalbased design method). The present paper examines the suitability of the numerical-based PISA design method for analyzing the pile response in sandy soil conditions. A concept design study for monopiles in dense sand is considered. Soil properties are based on realistic conditions encountered in the North Sea. The PISA methodology is compared with the methodology followed by the current design practice. Results are discussed and several conclusions are drawn providing factual insight into the applicability of the PISA design methodology for the design of monopiles in sand. @en

The PISA (Pile Soil Analysis) research project has resulted in a new methodology for the design of offshore wind turbine monopile foundations. A new software tool called PLAXIS Monopile Designer (MoDeTo) has been developed that automates the PISA design methodology. It facilitates the calibration of the so-called soil reaction curves by automated three-dimensional finite element calculations and it allows for a quick design of monopiles using the calibrated soil reaction curves in a one-dimensional finite element model based on Timoshenko beam theory. The monopile design approach has been validated for sand- and clay-type soils which are common in North Sea soil deposits. The paper presents a validation exercise based on the PISA research project proposal of a rule-based parametric model—General Dunkirk Sand Model (GDSM)—for Dunkirk sand as well as an application of the tool for a project involving an offshore wind turbine on a monopile foundation in sandy layered soil in which the PISA design is compared to the conventional API design. The paper concludes with a discussion of the results and the differences between the various methods.@en