FRP Offshore Structure Connections Optimization and Validation by Classification Society standards

Abstract

This paper discusses the use of composite materials in the design process of a horizontal bracing to column connection of an offshore semi-submersible platform to support two wind turbines. The geometry of the connection was optimized to improve the performance and reliability of the connection, columns and bracing tubes. These offshore foundations usually deal with massive structural tubes, and they are used to fit a huge amount of stiffeners. This paper will show how using some horizontal stiffeners combined with their intersection with horizontal bracings tubes, can improve drastically the behavior of the connection. A comparison between conventional materials (steel) and advanced materials (E-glass fibres and epoxy matrix) was performed and it was demonstrated how the use of composite materials makes necessary to modify the connection geometry and configuration to obtain an equivalent performance. This is due to the very different stiffness behavior shown by composites and steel. Therefore, the design of an offshore connection must be approached differently according to the used material. The composite laminate layout design process was also made. The material was evaluated using a Bureau Veritas normative note specifically applicable to composite ship hulls, but adapted to the needs of the materials used in this design, in terms of raw material requirements. The design process of a laminate panel of the connection is shown using the above mentioned standard. All data and results shown here were harvested within the scope of the European research project Fibregy (EU Horizon 2020, Ref. 952966).

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