Offshore wind energy is rapidly developing, motivated by the stronger and more regular winds at sea with respect to land areas. The present paper is part of a European research program (REFOS, 2016-2019), which aimed at the development of a deep-water offshore multi-purpose floating system suitable for producing simultaneously wind and wave energy.The system consists of a triangular platform supported by cylindrical floaters with the wind turbine mounted at the deck center (Central Floater - CF) and the cylindrical OWC devices at its three corners (Peripheral floaters - PF). Floaters consist of an external thin skin, reinforced with vertical and horizontal stiffness in the inner side. Peripheral and Central Floaters are connected with each other with a set of braces, welded on the outer side of the floaters’ skin. In a previous elementary study, a numerical model was developed, which included the whole platform. The results showed that the weakest points of the structure lie in the welded connection between the Peripheral Floaters and the Brace.The paper is presenting a detailed numerical model of the region around the connection of the brace with the skin, including the weldment and the inner stiffeners. The model was developed in the general-purpose finite element software Abaqus. For the brace and weldment 3D solid elements have been used, while for the stiffeners and skin 3D shell elements are employed. The floater’s skin is fixed and the load is applied at the top of the brace in the brace-to-shell plane (in-plane bending). The model was validated using experimental data from the response force of the hydraulic actuator and from strain gauges. Finally, the Stress Concentration Factor (SCF) is computed, the influence of stiffeners on local deformation is investigated, and critical regions are identified in terms of local stresses.

Mechanical Behavior of Brace-to-Cylinder Welded Stiffened Connections in Tlp Wind Energy Platforms

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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