The Total Probability Fatigue Reliability Analysis For The Deepwater Semi-submersible Platform

The deepwater semi-submersible platform is the major engineering equipment for exploiting oil and gas in ocean, which is able to adapt to bad sea conditions. Many major accidents happening to offshore drilling platforms are caused by structural fatigue damage, one ninth of which is due to fatigue under investigation, thus it's necessary to give a study on the fatigue reliability analysis for the deepwater semi-submersible platform.We offer an overall fatigue reliability analysis for key nodes in the deepwater semi-submersible platform with the total probability spectrum analysis, based on former relevant researches.The created deepwater semi-submersible platform model needs optimizing as calculation accuracy requires, particularly key parts of which demands remeshing.According to statistical data and JONSWAP wave spectrum, random response spectrum stress is calculated and compared after Morison and The Large Component Column wave spectrum on the column, and Morison wave spectrum on the brace are calculated. According to Miner linear cumulative fatigue damage theory and the probability analysis for random response beyond the damage boundary for the first time, we calculate and compare total probability fatigue reliability for key nodes in the structure, with the stress subjected to Rayleigh distribution and Weibull distribution.The total probability fatigue reliability for key nodes in the deep semi-submersible platform requires to be calculated in the complex conditions for further study. With five commonly used statistical regression methods, the corresponding curves for the fatigue reliability index and the maximum stress standard for key nodes in the platform structure in many short-term sea states are plotted to evaluate the security of the platform structure in its design life.