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Schaumann P.,Leibniz University of Hanover | Bechtel A.,Leibniz University of Hanover | Lochte-Holtgreven S.,Grbv Ingenieure im Bauwesen GmbH | Wilke F.,RWE Offshore Logistics Company GmbH

Grouted joints as hybrid tube-to-tube connections with high-strength concrete annulus are often used in monopile substructures for offshore wind energy conversion systems. Compared to jackets or tripods, grouted joints in monopiles are loaded by predominant bending moments. Currently, only a limited number of design and calculation methods for the stress design are available. Besides simplified engineering models based on linear shell theory, numerical calculation methods and models have been developed in recent years. Those models include material and geometrical nonlinearities of a grouted joint under predominant bending. In this paper three different analysis methods are presented, their accuracy is described by calculated and measured displacements and stresses. © 2014 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

Nernheim A.,RWE Offshore Logistics Company GmbH | Vasquez A.,RWE Offshore Logistics Company GmbH | Wilke F.,RWE Offshore Logistics Company GmbH | Kahle H.,RWE Offshore Logistics Company GmbH

Jack-up vessels are widely used for installation of foundations and turbines during the construction of offshore-windfarms. Equipped with moveable legs, these vessels are able to elevate their hull out of the water and provide a stable work platform. At the same time the leg-soil-interaction increases the complexity of the operation which is reflected in the requirement to perform site specific assessments at any jacking location. Subsequent to the description of the phases of a typical jacking operation the article outlines the main components of the geotechnical part of a site specific assessment. The governing load cases are introduced and an overview of the required soil investigations is given. In the following the focus is set on the determination of the bearing capacity and the derivation of related leg penetrations for the jack-up vessel. Phenomena like the "punch-through" and their effect on the process are explained. For a typical North Sea windfarm with non-cohesive soils the accuracy of the leg prediction is shown by comparison to measured data and the major influencing parameters are discussed. Finally, a CPT-based correction method for the capacity of the upper soil layers is introduced. Copyright © 2015 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin. Source

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