The Analysis Of The Design Criterion And Dynamic Reliability Assessment Of Existing Platform In Typhoon/hurricane Affected Region

Offshore platforms are the basic facilities for offshore oil exploitation and worker living. The extreme environment loading induced by typhoons and hurricanes in ever summer gives austere challenge to offshore platform structure. The platform will result huge economic loss and social impact in the event of platforms failure. Hurricane Katrina and Rita in 2005 resulted in the largest number of destroyed and damaged platforms in the history of Gulf of Mexico operations. The lessons from accident have taught us that the lower defence criteria of the platform and structure resistance reduction are the chief reason for the failure.In order to reduce the risk in the design stage and realize and command the reliability of existing platforms, this thesis performed three innovative studies as followed.●Based on the compound extreme value distribution, the concept of parameters design risk for ocean environmental load and Solving Method of platform deck elevation against the largest hurricane are proposed in this thesis.The risks in the design stage caused by uncertainties existing in extreme theory, sampling method, samples interval and statistics parameters solving method are discussed and the multivariate compound extreme value distribution (MCEVD) model is used to predict the deck elevation with different combination of tide, surge height and crest height.●Under the action of natural and service environments, the performance of structure in the course of long-term service will deteriorate gradually due to components defect, mechanical damage, fatigue and material deterioration, which would cause structural resistance and reliability to decrease.The research of time-dependent reliability has important theoretic and practical meaning. Previous studies pay more attention to the structure resistance deterioration while ignoring the dynamic characteristics of ocean environment loads.The deterioration of ultimate bearing capacity caused by corrosion and marine growth was research and the time-dependent reliability of environment loads solving calculation method which based on the Bayesian theory and equivalent load method was proposed in this thesis.The calculations predicted by this method were reasonable because of the environment loads updating.●All of the ocean oilfields are in the typhoon-affected region in China and the typhoon characteristics and disaster factors are different. For prevention and mitigation of typhoon disasters in offshore engineering, in this paper a double-layer nested model of typhoon disaster zoning and prevention criteria is proposed. Considering the frequency and intensity of typhoon and its induced disaster, the sea area zoning was proposed and it will supply reasonable references to decision-making of protection criterion and risk assessment for offshore engineering.