Fatigue Reliability Of New-type Deepwater Mooring Systems

Currently, the deep-sea exploration activities are growing constantly, which puts forward higher requirements to the mooring systems of the offshore platform structure. The new type of taut-wire mooring system is being widely used as the alternative of the conventional catenary mooring system. This article summarizes the merit and demerit of the new tension-type mooring system and traditional catenary mooring system, and then study the fatigue reliability of the Taut-wire mooring system. The research achievements of the domestic and overseas study on the fatigue reliability of the Taut-wire mooring system are summarized, together with the prospect to the further research in order to supply significant reference for study and application on this special subject in our country.The new type of taut-wire mooring system is influenced by wind, wave, current, and have some initial tension, so its synthetic material is easy to generate fatigue failure under fatigue loadings. This paper establish the taut-wire mooring system with the finite element software ANSYS. This paper use the modal analysis and spectrum analysis method to solve the stress spectrum of the deep-water taut-wire mooring rope, and use the Miner linear cumulative damage theory and the T-N curve model to study the fatigue reliability of the deep-sea mooring system. The long-term stochastic wave load process was divided into k short-term cases which are distributed as Rayleigh in the paper. Fatigue reliability of a single mooring rope and the entire mooring system will be analyzed in this paper, and investigate the impact of different initial pre-tension on the fatigue reliability of the mooring rope, some significant conclusions are concluded.