Stability analysis of an oceanic structure using the Lyapunov method

Purpose-A tension leg platform (TLP) is a vertically moored, floating structure which is normally used for offshore oil/gas production. However, these types of structures can be damaged by vibration responses that are too large. The purpose of this paper is to consider the influence of the external waves on oceanic structures. Design/methodology/approach-A mathematical model of an ocean environment was constructed, in which wave-induced flow fields cause structural surge motion, then solutions to the mathematical model were analytically derived. Findings-The Takagi-Sugeno (T-S) fuzzy model is employed in the approximation of the oceanic structure. The stability analysis of the TLP system is carried out using the Lyapunov direct method. Practical implications-The dependence of the wave-induced flow field and its resonant frequency on the wave characteristics and the structural properties of the platform, which include width, thickness and mass, can be drawn using a parametric approach. Originality/value-Mathematical modeling is applied to find the wave-induced displacement due to the surge motion. The vibration of the mechanical motion of the platform structure caused by wave force is also discussed.