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Load bearing behaviour of grouted joints subjected to predominant bending
The large-scale generation of electricity from wind offshore shall contribute significantly to the targets of energy and climate policy in a number of countries, including Germany. As a consequence, a rapid growth of this industry sector is to be expected, if reliability is increased and economic optimization can be realized in the next years. One of the keys for optimization of offshore wind projects is the deployment of cost-effective and safe support structures. A major part of most of these support structures are grouted joints, not only for jackets but especially important for monopiles. Monopiles have been considered in the past as limited to medium water depths and smaller turbines. Due to the recent developments in the manufacturing equipment of large diameter tubes and installation vessels, there is a strong tendency to extend their application to deeper water and larger turbines. Therefore, this thesis examines the bearing behaviour of currently used slender grouted joints subjected to predominating bending. Besides the interaction of the ductile steel shells with the brittle grout material, this work focuses on the analysis of the characteristics of shear keys in the connection under combined loading and their adequate representation in the design process. Due to the limited test experience for grouted joints subjected to predominant bending, a test programme has been executed which comprises large and small scale tests under different types of loading. While the small scale tests mainly have been performed to gain knowledge about the local behaviour of the high strength material and to obtain base data for benchmarks of the numerical models, the large scale tests have been executed with realistic dimensions and static and dynamic loading. The tests confirmed that application of shear keys in the inner third of the connection effectively increases the robustness of the grout connection and distinctly reduces damage from ovalization. Local investigations showed only minor deterioration around the shear keys. This demonstrates that further economic optimization is possible. On basis of the test results, numerical models have been developed and validated. Besides the implementation of a material model for adequate representation of the local grout characteristics, the development of a novel combined spring element-contact model for shear keyed connections forms main part of the analyses. Aligned to this model, a design approach for the local zone around the shear keys and the numerical derivation of parametric shear key fatigue classes is presented.
Load bearing behaviour of grouted joints subjected to predominant bending
The large-scale generation of electricity from wind offshore shall contribute significantly to the targets of energy and climate policy in a number of countries, including Germany. As a consequence, a rapid growth of this industry sector is to be expected, if reliability is increased and economic optimization can be realized in the next years. One of the keys for optimization of offshore wind projects is the deployment of cost-effective and safe support structures. A major part of most of these support structures are grouted joints, not only for jackets but especially important for monopiles. Monopiles have been considered in the past as limited to medium water depths and smaller turbines. Due to the recent developments in the manufacturing equipment of large diameter tubes and installation vessels, there is a strong tendency to extend their application to deeper water and larger turbines. Therefore, this thesis examines the bearing behaviour of currently used slender grouted joints subjected to predominating bending. Besides the interaction of the ductile steel shells with the brittle grout material, this work focuses on the analysis of the characteristics of shear keys in the connection under combined loading and their adequate representation in the design process. Due to the limited test experience for grouted joints subjected to predominant bending, a test programme has been executed which comprises large and small scale tests under different types of loading. While the small scale tests mainly have been performed to gain knowledge about the local behaviour of the high strength material and to obtain base data for benchmarks of the numerical models, the large scale tests have been executed with realistic dimensions and static and dynamic loading. The tests confirmed that application of shear keys in the inner third of the connection effectively increases the robustness of the grout connection and distinctly reduces damage from ovalization. Local investigations showed only minor deterioration around the shear keys. This demonstrates that further economic optimization is possible. On basis of the test results, numerical models have been developed and validated. Besides the implementation of a material model for adequate representation of the local grout characteristics, the development of a novel combined spring element-contact model for shear keyed connections forms main part of the analyses. Aligned to this model, a design approach for the local zone around the shear keys and the numerical derivation of parametric shear key fatigue classes is presented.
Load bearing behaviour of grouted joints subjected to predominant bending
Wilke, Fabian (Autor:in)
2014
289 Seiten, Bilder, Tabellen, Quellen
Hochschulschrift
Englisch
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