Structural Design of a Semi-Submersible Platform With Water-Entrapment Plates Based On a Time-Domain Hydrodynamic Algorithm Coupled With Finite-Elements

Abstract

This paper discusses the structural analysis of a semi-submersible-type platform with heave plates at the base of each column, designed to develop marginal fields in ultra-deepwater. The geometry consists of three vertical rectangular columns and three pontoons with large horizontal skirts extending in all directions from the base of the columns. The skirts are subjected to significant hydrodynamic forces due to diffraction-radiation loads and viscous effects around their edges. Both extreme and fatigue analyzes of the structural members are necessary to ensure the integrity of the structure and the optimization of the hull weight. Due to the novel geometry, the modes resulting in the largest stress levels are expected to differ from conventional semisubmersible design. A systematic approach is implemented to determine the design load cases. This work highlights the necessity to run a comprehensive structural analysis combined with a hydrodynamic model in order to assess all possible failure modes.