A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Cyclic loading design of offshore wind turbine foundations
Offshore wind turbines (OWT) are slender flexible structures that continu-ously swing owing to the harsh offshore conditions. During the lifetime of a wind turbine’s foundation, various forms of cyclic and dynamic loads, such as wind, waves, currents, typhoons, and earthquakes can interfere with the operation of its structure and potentially cause a premature shutdown. It can be observed from the soil–structure interaction that cyclic loads cause the saturated soil to experience an accumulation of permanent deformation and an increase in the pore water pressure, which eventually, leads to the tilting of the foundation. In terms of serviceability limit state (SLS), geotech-nical engineers have to ensure that the foundation does not exceed the op-erational tolerance prescribed by the wind turbine manufacturer, e.g., 0.25°, throughout its lifetime. However, upon reviewing the relevant code of prac-tice, it would be evident there are no validated and generally accepted methodologies that are recommended to assess the SLS. In this research project, an accurate, versatile, and user-friendly method, called the soil cluster degradation method (SCM), is developed. This method can predict the lifelong deformation due to soil–structure-interaction for offshore wind turbines, which are subjected to a series of regular cyclic loads. This method bases its prediction on (i) three-dimensional (3D) finite element modelling (FEM), which enables an accurate computation of stress redistribution around the foundation and (ii) a series of cyclic laboratory tests. Moreover, this thesis aims to provide confidence to geotechnical engi-neers on implementing this method in day-to-day projects. Different numer-ical tools were proposed for improving the cyclic laboratory test campaign and the proposed method was validated with a full-scale test on a gravity-based foundation, which was subjected to hundreds of thousands of load cycles. Finally, a reliability-based-design (RBD) methodology was proposed to address the main source of uncertainty involved in verifying the SLS cri-teria and designing the foundation to an annual reliability target level. The outcome of this research provides a reliable tool to the foundation designers to deliver cost-effective and low-risk offshore wind turbine foundations, where the foundation tilting has to be predicted during the structure life-time.
Cyclic loading design of offshore wind turbine foundations
Offshore wind turbines (OWT) are slender flexible structures that continu-ously swing owing to the harsh offshore conditions. During the lifetime of a wind turbine’s foundation, various forms of cyclic and dynamic loads, such as wind, waves, currents, typhoons, and earthquakes can interfere with the operation of its structure and potentially cause a premature shutdown. It can be observed from the soil–structure interaction that cyclic loads cause the saturated soil to experience an accumulation of permanent deformation and an increase in the pore water pressure, which eventually, leads to the tilting of the foundation. In terms of serviceability limit state (SLS), geotech-nical engineers have to ensure that the foundation does not exceed the op-erational tolerance prescribed by the wind turbine manufacturer, e.g., 0.25°, throughout its lifetime. However, upon reviewing the relevant code of prac-tice, it would be evident there are no validated and generally accepted methodologies that are recommended to assess the SLS. In this research project, an accurate, versatile, and user-friendly method, called the soil cluster degradation method (SCM), is developed. This method can predict the lifelong deformation due to soil–structure-interaction for offshore wind turbines, which are subjected to a series of regular cyclic loads. This method bases its prediction on (i) three-dimensional (3D) finite element modelling (FEM), which enables an accurate computation of stress redistribution around the foundation and (ii) a series of cyclic laboratory tests. Moreover, this thesis aims to provide confidence to geotechnical engi-neers on implementing this method in day-to-day projects. Different numer-ical tools were proposed for improving the cyclic laboratory test campaign and the proposed method was validated with a full-scale test on a gravity-based foundation, which was subjected to hundreds of thousands of load cycles. Finally, a reliability-based-design (RBD) methodology was proposed to address the main source of uncertainty involved in verifying the SLS cri-teria and designing the foundation to an annual reliability target level. The outcome of this research provides a reliable tool to the foundation designers to deliver cost-effective and low-risk offshore wind turbine foundations, where the foundation tilting has to be predicted during the structure life-time.
Cyclic loading design of offshore wind turbine foundations
Design von zyklisch beanspruchten Gründungen von Offshore-Windenergieanlagen
Zorzi, Gianluca (author) / Technische Universität Berlin (host institution)
2022
Miscellaneous
Electronic Resource
English
DDC:
624
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