Research On Risk Based Inspection (RBI) For Jacket Platform Structure

It is of great significance to select the hot spot for testing and maintaining scientifically in order to elevate its efficiency, since it's extremely expensive for platform test and maintenance offshore, especially the tasks under water. The traditional spot testing and selecting is based on various qualitative criterion, which is not only unscientific but also large amount of work. The purpose of this paper is to establish a risk-based method of jacket platform inspection, which considers of the risk rank of platform structure as well as the results of fatigue strength assessment, to scientifically screen out the specific position of the jacket platform that needs a test at service, increasing the efficiency of testing and maintaining.The context of work:1. Develop a method appropriate to the importance analysis of the jacket platform component. Apply environmental loading in one-hundred-year storm condition to calculate the ultimate bearing capacity of global platform using collapse analysis, on the basis of which,comparing the bearing capacity of the platform removed of one component with the complete platform to make out the importance of the removed component.2. Research the reliability analysis method of the global structure and separate component of platform. Weibull distribution with three parameters is applied to the parameter regression analysis in extreme sea state, considering of the variability of main structure parameters. Calculate failure probability of the platform system with Monte Carlo method and of the separate component with equations in four kinds of extreme state.3. Draw up the programme of risk-based inspection plan. Calculate the risk matrix of the platform system and the separate component with the results of component importance and reliability calculation, screening out the hot spot with higher risk according to the risk matrix,sequentially determining the risk-based inspection plan.4. Apply fatigue analysis to hot spot screened out of the risk matrix with the results of the risk-based inspection analysis, which determines the fatigue-based inspection plan.5. Comprehensively comparisive the risk-based inspection plan and the risk-based inspection plan to determine the ultimate inspection plan of platform.