Simplified fatigue assessment for deepwater semi-submersible rig

This paper focuses on simplified fatigue assessment for deepwater semi-submersible rig in South China Sea.According to wave long-term distribution of South China Sea,the parameters for the long-term Weibull distribution of stress range of the global structure are calculated.Once-in-a-lifetime wave loads are forecasted for the rig,and once-in-a-lifetime hot spot stress range of the structures are calculated using once-in-a-lifetime wave loads.The structural fatigue life is calculated by the simplified fatigue assessment method,and the results are compared with the results of the spectral-based fatigue assessment method.The results show that the simplified fatigue assessment method is relatively safe and can be used for design.