Behaviour of Suction Bucket Foundations for Offshore Wind Energy Converters under Cyclic Loading

吸桶是海上风能转换器的另一种基础类型。由于它们的安装被广泛证明是无噪声排放的，它们可以用来代替通常的海上基础与打入桩。由风浪和水波引起的循环荷载在吸力桶型基础设计中起着特殊的作用。这些荷载会导致基础性能的变化。由于缺乏循环响应的经验，需要进行大量的研究以确保吸桶基础在其计划使用寿命期间的稳定性。因此，拟议研究项目的主题是吸力桶基础的数值和实验研究，以便定量确定循环荷载引起的其行为变化。在有限元分析的框架下，考虑到饱和土中土体永久变形和超孔隙水压力的积累，将研究吸力桶在循环轴向和侧向荷载下的响应。因此，饱和砂土的模拟将采用完全耦合的两相模型和欠塑性本构模型相结合的方法。在模型试验中，将研究在循环轴向和横向荷载作用下基础响应的长期变化。这些研究将得出重要的结论，从而可靠地确定循环动力载荷对吸力桶性能的影响。在此基础上，提出了一种估算循环加载吸油桶位移和旋转的设计方法。因此，可以实现承受循环载荷的吸力桶的经济尺寸，并显著提高海上风能变流器的运行可靠性。

Suction buckets are an alternative type of foundation for offshore wind energy converters. Due to their widely proved noise-emission-free installation, they can be used instead of the usual offshore foundations with driven piles. Cyclic loads, induced by wind and water waves, play a special role in the design of suction bucket foundations. These loads can lead to changes in foundation behaviour. Due to lack of experience on cyclic response, extensive studies are required to ensure the stability of suction bucket foundations throughout their planned service-life time. Therefore, the subject of the proposed research project is the numerical and experimental investigation of the suction bucket foundations in order to quantitatively determine the changes in their behaviour caused by the cyclic loads. In the framework of the finite element analyses, the response of suction buckets subjected to cyclic axial and lateral loads will be investigated, taking into account the accumulation of permanent soil deformations and excess pore water pressures in saturated soil. Therefore, a fully coupled two-phase model combined with a hypoplastic constitutive model will be used for the modelling of the saturated sandy soil. In the model test, the long-term changes in foundation response, which are induced by cyclic axial and lateral loads, will be studied. The investigations should lead to important findings with which the effects of cyclic-dynamic loadings on the behaviour of suction buckets can be reliably determined. Based on these results, a design method for the estimation of the displacements and rotations of cyclic loaded suction buckets will be developed. Thus, an economic dimensioning of suction buckets subjected to cyclic loads, as well as a significant increase in the operational reliability of offshore wind energy converters can be achieved.