Concept Design Study of Laterally Loaded Monopiles in Sand

Abstract

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.