Fatigue Life Analysis Of CT-Spar And The Design Of The Mooring System

It is necessary to design and research high-performance platform with the oil industry's development from land to deep sea. Recent years a variety of different types of deep-sea platform emerged, such as the semi-submersible platform, TLP platform and so on. But by virtue of relatively benign motion performance and low cost, Spar platform has become the Oil and Gas Company's new darling. Based on the former generations of Spar platforms, the present paper brings in a new Spar concept- the Cell-Truss Spar. Because the CT-Spar platform is an innovative platform and is still in the conceptual design and preliminary structure design stage, we need to do more research for it. On the background researches have been done from two aspects. On the one hand, the fatigue life of the key joint of the Spar has been carried, which is the important judgment standard of the structure performance; on the other hand, the design and the yield strength analysis of the mooring system has been down. The study will give valuable technical support for future design and research of the CT-Spar in China.This paper research work is as follows, 1) The development process of the Spar was demonstrated, then the main structure dimension and the merit of CT-Spar were introduced. Based on the document, the key points which easily cause the fatigue damage be selected.2) Spectral-based method is provided to analyze the fatigue life of the key joint. First, the FEA models are established and the global FEA analyses in different cases are performed, which supplies boundary conditions of local key joints in local stress analysis. Then, hot spot stress method is used to get the stress transform of the key joint with which stress spectrum and stress spectrum parameters in each short-term sea state can be calculated. Finally, the Palmgren-Miner's rule is applied to calculate the fatigue life of the key joint. According to the results, the fatigue life of the key joint can meet the requirement. the fatigue life of the key joint can meet the requirement.3) First, the environment loads are demonstrated detailedly. Then the platform mooring system design program is proposed. By using HydroD Program the motion performances are done. Finally, using Mimosa program to calculate the yield strength in all kinds of cases. Compare to the results, we will know that the mooring system is fit for the Spar platform.