Requalification of Offshore Platforms on the Basis of Inspection Results and Probabilistic Analyses

The paper presents an integrated engineering approach utilised to requalify four steel gravity platforms, installed offshore Congo in the 1970's, for an operating life extended over the original design requirements. The main subjects outlined in the paper are: (1) Features of the Inspection data bank fully integrated with the Structural data bank, (2) Criteria to correlate damage to joint characteristics to define probability distributions of representative deterioration parameters for non-inspected joints, (3) Definition of the stochastic models for the random variables to be used in fatigue probabilistic risk analysis, (4) Identification of possible collapse mechanisms, (5) Definition of the failure probability of the system, (6) Recommended long term IRM programme, and (7) Discussion on economic aspects related to the allowable extension of the platform's operating life.