This paper addresses the issue of offshore platform reanalysis and requalification. Fundamental aspects regarding the decision process for platform requalification are first presented, decision making criteria are then discussed and a framework for structural reanalysis is proposed. Case studies are presented to illustrate the applicability of the aforementioned approach. The first example evidences how significant for requalification purposes can be the reassessment of the design loads on the basis of newly acquired knowledge. The second example describes the implementation of a probabilistic fracture mechanics approach utilized to requalify steel gravity platforms.
Offshore exploitation is nowadays a mature field. Several platforms have been on operation for over twenty years, often exceeding their original design lifetime and experiencing extreme environmental actions, damages and possible reduced maintenance and repair due to periods of depressed international offshore market. Requalification of these structures for extended lifetime is now a major issue in the offshore industry. Thereby important restrictions shall be considered due to the fact that offshore operators must balance their decisions against required levels of safety and available budgets. The aforementioned reasons have resulted in the rationalization of the decision process and of the reanalysis procedures necessary to requalify existing offshore structures. Efficient and sophisticated techniques have been developed in the last five years for that purpose which incorporate modern structural and reliability analysis methods. This paper addresses the issue of offshore platform reanalysis and requalification based on the experience gained from several fitness for purpose analyses of jacket platforms in the Adriatic Sea and offshore West Africa. Fundamental aspects regarding the decision process for platform requalification are first addressed, decision making criteria are then discussed and a framework for structural reanalysis is proposed. Case studies are presented to illustrate the applicability of the aforementioned approach.
