Load utilisation (LU) ratio of monopiles supporting offshore wind turbines: Formulation and examples from European Wind Farms. (15th March 2022)

• Record Type: Journal Article
• Authors: Aleem, Muhammad; Bhattacharya, Subhamoy; Cui, Liang; Amani, Sadra; Salem, Abdel Rahman; Jalbi, Saleh
• Is Part Of: Ocean engineering. Volume 248(2022)
• Publication Date: 2022-03-15
• Subjects: Offshore wind turbines -- Soil structure interaction -- Soil resisting capacity -- Load utilisation -- Moment capacity -- Lateral capacity; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2022.110798
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Offshore wind farms are currently being constructed worldwide, and most of the Wind Turbine Generator (WTG) structures are supported on single large-diameter steel piles, commonly known as monopile. One of the challenging design aspects is predicting the long-term deformation of the foundation and, in particular, the accumulation of rotation which is a complex Soil-Structure Interaction (SSI) problem. Accumulation of rotation requires the estimation of Load Utilisation (LU) ratio (i.e., ratio of the load-carrying capacity of the foundation to the applied loads from wind and wave). Estimation of LU for monopile is not trivial due to the simultaneous action of lateral load and moments and needs the introduction of interaction diagram concepts. This paper proposes methodologies to obtain LU for monopiles using three types of methods: (a) Simplified method, which is based on closed-form solution (where the load effects are uncoupled) and can be carried out using spreadsheets or pocket calculators; (b) Standard method based on non-linear Winkler spring (also known as p-y method) where the load effects are also uncoupled; (c) Advanced method, which uses Finite Element Method (where the load effects are coupled). Examples of monopiles are taken from European Wind Farms covering different ground profiles: Gunfleet Sands (clay profile), Walney-I (sandy profile), London Array-I (layered profile) and Barrow-II (layered profile) sites are analysed using all three methods. It is hoped that the methodology will be helpful in the design optimisation stage. Highlights: Load Utilisation (resistance divided by applied actions) ratio for monopiles. Closed form solution for load utilisation ratio. Simplified, standard and advanced method of analysis. Examples from European wind farms to show the methodology