Mostafa Zeinoddini - Prof, K. N. Toosi University of Technology and TWI Persia
Iman Ahmadi - Structural Section, TWI Persia, NIOC
Hadi Khalili - Structural Integrity Section, TWI Persia
Hamid Golpour - Structural Integrity Section, TWI Persia

Estimation of fatigue life is of great importance in offshore platforms. The fatigue life is considered to be acceptable and within normal design criteria if the calculated fatigue life is longer than the total design service lifetime multiplied by the Fatigue Safety Factor (FSF). Actual fatigue life of an existing platform typically deviates from that intended by its designer because aging platforms commonly experience some degradation, mechanical damages, repairs, modifications and come across demands for the service extension. Butt weld tubular is typical connection in the offshore platforms and fatigue damage calculation of this type joints has been completely outlined in the conventional standards (for example API RP2A and NORSOK-N006). However, fatigue life calculations of other type of connections have not clearly been addressed. The current paper focuses on different aspects of the remaining fatigue life assessment of pinned connections in an aging platform. In the course of a case study, it describes methods for a spectral fatigue modeling and analysis of the fatigue damages to welded joints and pinned connections. Potential limitations in the available codes of practice, regarding the fatigue life assessment of existing offshore structures are also highlighted

structural integrity assessment, aging platform, pinned connections, fatigue analysis, remedy measures