Reliability analysis of offshore wind turbine foundations under lateral cyclic loading

Abstract

Abstract. The design of foundations for offshore wind turbines (OWT) requires the assessment of the long-term performance of the soil–structure-interaction (SSI) which is subjected to a large number of cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that the foundation does not exceed the operational tolerance prescribed by the wind turbine manufacturer throughout its lifetime. This work aims at developing a probabilistic approach along with a reliability framework with emphasis on verifying the SLS criteria in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties, in the constitutive soil model for cyclic loadings and extreme environmental conditions and verifies that the foundation design meets a specific target reliability level. A 3D finite element (FE) model is used to predict the long-term response of the SSI accounting for the accumulation of permanent cyclic strain experienced by the soil. The proposed framework is employed for the design of a large diameter monopile supporting a 10 MW offshore wind turbine.

Derivation of Contour Plots for the Characterization of the Behaviour of Sand under Undrained Loading

“…Figure 2). The power law function given in Equation ( 4) is often used in the literature and practice (see e.g., [24][25][26]):…”

“…For each 𝑅 value and a given MSR, a set of regression parameters, 𝑎 , 𝑏 and 𝑐̅ , has to be determined. Zorzi et al (2019) [24] kept the parameter 𝑏 constant at −0.35, similar to Boukpeti et al (2014) [25] for carbonate silt sediments. Both author groups fitted shear strain plots instead of excess pore pressure ratios.…”