Shell buckling simulations of suction buckets with stochastic and deterministic imperfection forms

Abstract

Suction buckets are large shell structures that have become a prominent alternative to pile foundations for bottom-fixed and floating offshore wind turbines. They are embedded by applying negative pressure, which leads to a high risk of structural buckling during the installation. The prediction of the buckling strength of such large shells is subject to uncertainty, since it depends significantly on the initial geometric imperfections resulting from the fabrication process. The aim of this work is to understand and reduce uncertainties in the determination of the buckling pressure. Previous work on suction buckets revealed that the choice of a representative imperfection form and amplitude is very challenging and has not yet been solved in a generalized manner. In this work, a stochastic modeling approach is introduced, which considers more realistic imperfection patterns. This approach is compared to widely established imperfection forms such as buckling mode affine imperfections and analytically described weld depressions. The generated imperfection patterns are applied to geometrically and materially nonlinear finite element models and the buckling pressures are calculated. By quantifying the impact of different imperfection forms and amplitudes, uncertainties can be reduced, and design optimization and cost minimization are enabled.