Offshore wind turbines (OWTs) have emerged as a reliable source of renewable energy, witnessing massive deployment across the world. While there is a wide range of support foundations for these structures, the monopile and jacket are most utilized so far; their deployment is largely informed by water depths and turbine ratings. However, the recommended water depth ranges are often violated, leading to cross-deployment of the two foundation types. This study first investigates the dynamic implication of this practice to incorporate the findings into future analysis and design of these structures. Detailed finite element (FE) models of Monopile and Jacket supported OWTs are developed in the commercial software, ANSYS. Nonlinear soil springs are used to simulate the soil-structure interactions (SSI) and the group effects of the jacket piles are considered by using the relevant modification factors. Modal analyzes of the fixed and flexible-base cases are carried out, and natural frequencies are chosen as the comparison parameters throughout the study. Second, this study constructs a few-parameters SSI model for the two FE models developed above, which aims to use fewer variables in the FE model updating process without compromising its simulation quality. Maximum lateral soil resistance and soil depths are related using polynomial equations, this replaces the standard nonlinear soil spring model. The numerical results show that for the same turbine rating and total height, jacket supported OWTs generally have higher first-order natural frequencies than the monopile supported OWTs, while the reverse is true for the second-order vibration modes, for both fixed and flexible foundations. This contributes to future design considerations of OWTs. On the other hand, with only two parameters, the proposed SSI model has achieved the same accuracy as that using the standard model with seven parameters. It has the potential to become a new SSI model, especially for the identification of soil properties through the model updating process.

中文翻译：

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单桩和夹套支撑海上风力涡轮机的比较模态分析，包括土壤-结构相互作用

海上风力涡轮机 (OWT) 已成为可靠的可再生能源来源，见证了世界各地的大规模部署。虽然这些结构有多种支撑基础，但迄今为止使用最多的是单桩和导管架；它们的部署很大程度上取决于水深和涡轮机额定值。然而，建议的水深范围经常被违反，导致两种基础类型的交叉部署。本研究首先调查了这种做法的动态影响，以将研究结果纳入这些结构的未来分析和设计中。Monopile 和 Jacket 支持的 OWT 的详细有限元 (FE) 模型在商业软件 ANSYS 中开发。采用非线性土弹簧模拟土-结构相互作用(SSI)，并利用相关修正因子考虑套管桩的群效应。对固定和柔性基础案例进行了模态分析，并在整个研究过程中选择固有频率作为比较参数。其次，本研究为上面开发的两个有限元模型构建了一个少参数的 SSI 模型，旨在在有限元模型更新过程中使用更少的变量而不影响其模拟质量。最大横向土壤阻力和土壤深度使用多项式方程关联，这取代了标准的非线性土壤弹簧模型。数值结果表明，对于相同的涡轮额定值和总高度，护套支撑的OWT通常比单桩支撑的OWT具有更高的一阶固有频率，而对于固定和柔性基础的二阶振动模式则相反。这有助于 OWT 的未来设计考虑。另一方面，仅使用两个参数，所提出的 SSI 模型已达到与使用具有七个参数的标准模型相同的精度。它有可能成为一个新的 SSI 模型，特别是通过模型更新过程来识别土壤特性。所提出的 SSI 模型已达到与使用具有七个参数的标准模型相同的精度。它有可能成为一个新的 SSI 模型，特别是通过模型更新过程来识别土壤特性。所提出的 SSI 模型已达到与使用具有七个参数的标准模型相同的精度。它有可能成为一个新的 SSI 模型，特别是通过模型更新过程来识别土壤特性。