GUA&GSA Based Quantitative Risk Assessment Of Fixed Platform

The marine fixed platforms are frequently influenced by typhoon or storm induced extreme sea conditions, such as wind, wave, surge, current or ice action in the sea and lay in the structural failure risk induced by the extreme combined sea environment loads, so that the risk assessment of platform is one of the most important problems for scientists and engineers.In this thesis, the Quantitative Risk Assessment (QRA) is applied to analyze platform structure damage for evaluating the structure failure probability and damage consequence quantitatively. Based on the QRA, more reasonable decision-making about structure failures can be obtained.In this thesis, a QRA model of fixed platform is established for analyzing the structure failures induced by the extreme sea loads. The QRA model has a strong ability of analyzing adequately kinds of uncertainty in procedure of QRA and the superiority can be showed in three aspects. At first, the full probability method is used to research the cause of structure failures. That makes it feasible to analyze the influence of uncertainty on structure failure as comprehensively as possible. The second, the software ISPUD is used to evaluate the structure failure probability and the global uncertainty analysis (GUA) of some important random variables in model input space of risk assessment can be performed. The third place, the global sensitivity analysis (GSA) can also be performed by using the standard rank regress coefficient method (SRRC) to quantify the each contribution of model input variables to uncertainty of assessing results.As an application example, the above quantitative methods is practically used in the assessment of collapse risk of CB12-C platform structure system in Bohai sea and is proved be valid.