Structural Risk Assessment For Fixed Platform And Its Application

By requirement of risk assessment system in offshore oil industry in China, based on quantitative risk assessment, considering the extreme sea environments such as typhoon induced wind speed, wave, surge and astronomical spring tide bring serious destroy to platform structure failure, this thesis proposes elementary theory frame for structural risk assessment for fixed platform. As their applications examples, the risk assessment of platform deck clearance and overturning moment for platform failure is evaluated for Chengbei 12-C platform. Based on the historical data offered by DNV, suitable analysis of failure consequence including individual risk and social risk is taken into account. In analysis, the " stochastic simulation technique for non-Guassian multivariate random variables with different correlations" is used to solve failure probability. The uncertainties analysis of input sea environmental factors are involved in risk assessment system, which will improve the structural safety analysis. The job of this thesis includes the following content mainly:Based on quantitative risk assessment, this thesis proposes suggestion and establishes corresponding system for structural risk assessment of fixed platform. In this approach, sufficiently considering influence and effect of extreme sea environments for platform, applying joint probability theory to risk evaluation, and using stochastic simulation technique—importance sampling procedure to solve failure probability.Taking chengbei 12C platform as example to analyze deck clearance and integral failure. Considering the typhoon induced sea environment factors such as wind, wave, current, and storm surge, using the "stochastic simulation technique for non-Guassian multivariate random variables with different correlations" is to solve joint probability, and involves the uncertainty analysis for input parameters in risk analysis.The historical statistical data by DnV are used to analyze individual risk and social risk brought by failure of platform. The risk matrix expressing different risk value and influence of all kinds of factors to risk value is evaluated.