Abstract The design of monopile foundations for offshore wind turbine structures is dominated by requirements resulting from serviceability and fatigue limit state. To fulfil these criteria, the load deflection-behaviour and therefore long-term accumulations of permanent deflections and rotations of the monopile foundation due to cyclic occurring wind and wave loads have to be predicted. In this paper a brief overview on current design code practice as well as other proposed methods for the prediction of accumulated deflections or rotations is given. Further, the results of a systematic model test study dealing with the response of monopiles to lateral cyclic loading in medium dense sand at different cyclic load ratios, load eccentricities and pile embedment lengths are described and evaluated. The observations of the model test study are supplemented by results of a second test series involving the visualisation of displacement fields around laterally loaded piles by means of particle image velocimetry. Based on the findings and the results of previous experimental investigations, recommendations regarding the prediction of displacement accumulations for large diameter monopiles in sand are given.

中文翻译：

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沙地海上风电机组单桩循环横向响应影响参数的试验研究

摘要 海上风电机组结构单桩基础的设计主要受适用性和疲劳极限状态的要求。为了满足这些标准，必须预测载荷挠度行为，因此必须预测由于周期性发生的风和波浪载荷而导致的单桩基础永久挠度和旋转的长期累积。在本文中，简要概述了当前的设计规范实践以及用于预测累积挠度或旋转的其他建议方法。此外，还描述和评估了系统模型试验研究的结果，该研究涉及在不同循环载荷比、载荷偏心距和桩埋置长度下中密砂中单桩对横向循环载荷的响应。模型试验研究的观察结果得到了第二个试验系列的结果的补充，该试验涉及通过粒子图像测速法对横向受力桩周围位移场的可视化。根据以往实验研究的发现和结果，给出了关于预测砂中大直径单桩位移累积的建议。