Numerical Study on the Bearing Reliability of the Bucket Foundation for Offshore Wind Turbines under Scour Erosion: A Case Study

Abstract

To address the critical issue of local scour, which affects large-diameter bucket foundations supporting offshore wind turbines, this study develops a computationally efficient reliability analysis framework that integrates failure envelope theory with copula functions. Traditional methods struggle to define explicit performance functions under combined loading conditions. This research overcomes this limitation by establishing validated three-dimensional finite element models to derive failure envelopes at various scour depths. Then, maximum entropy models are coupled with a Gumbel–Hougaard copula to capture nonlinear relationships between marine environmental parameters, enabling the efficient processing of 200 000 environmental load cases using MATLAB. The bearing failure probability of the bucket foundation is then assessed by comparing these load cases against the corresponding failure envelopes. The case study results demonstrate that scour significantly reduces the elliptical failure envelope. At a scour depth of 0.5H_B (bucket height), the horizontal ultimate bearing capacity decreases by 38.2%, whereas the moment ultimate capacity decreases by 14.9%. Increasing the scour depth (S_d) from 0.1H_B to 0.5H_B reduces the reliability index by 6.2%–25.5% compared with the no-scour condition. This failure-envelope-based method provides an innovative, cost-effective solution for quantifying real-time operational reliability under evolving scour conditions.

Keywords

Failure envelope of bucket foundation / Maximum entropy model / Local scouring / Failure probability / Reliability analysis

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