| This paper is based on the"863"High Technology Research and Development Program of China of"Research on Life Extension Technology for Aged Offshore Platforms"and the National Natural Science Foundation Program (50679083) of"Research on Life Prediction Methods and Management Theory of Aged Offshore Platforms for Life Extension". The residual strength and safety reliability is studied for complex ocean environment. Considering the complexity and uncertainty of loads, applying the certainty method, multilevel assessment method, reliability analysis and quantitative risk assessment method, the risk assessment theory framework and assessment method is obtained through the study for aged platform. The main works are summarized as follows:(1)The influence of different damage types for aged offshore platform member on the global load bearing capacity and reliability is studied. The certainty method of pile-soil nonlinearity spring model is developed by using MATLAB and VC software creating load-displacement program. The global safety assessment method for aged platform under extreme load is studied based on certainty method.(2)Considering the load randomness and accumulated load, the frequency domain method and time domain method is studied for platform random fatigue life prediction and safety assessment. The fatigue load spectral is obtained through spectral analysis method, and the stress concentration factor of pipe joint get through ANSYS. The key area for fatigue check of jacket and jack-up platform is indicated.(3)The fatigue reliability of aged offshore platform under accumulated load is used as an example, and the reliability index is computed based on spectral analysis method. The limit status equation is developed by using fatigue accumulated damage as control parameter, and then the reliability index compute expression is obtained. The reliability analysis method for platform system is studied, and the structure system reliability of both intact and aged platform is analyzed, and the results are compared through a computing example.(4)The FE modeling method for jack-up platform is studied. The dangerous area and key area which should pay attention is analyzed, through global strength calculation and pile stability check by ANSYS. Weakness of the platform was analysed. The hidden trouble and its influence on structure were studied, and the assessment method was given for platform life extension period. The main failure mode and discretion index for aged platform is analyzed. The failure modes for jacket and jack-up platform are analyzed. The main failure event, event frequency and the consequence is studied. And then the quantitative risk assessment method is studied through analysis example of quantitative risk computing on platform static strength and crash event failure. The risk for platform structure can be quantitative assessed by this method, and then the risk of overall system is obtained. The risk acceptance standard, risk control measurement and risk management is studied.
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