Life-cycle assessment of marine civil engineering structures

Based on operational experiences with offshore structures it is argued that adequate structural safety should be ensured by proper design, fabrication and operational criteria as well as by proper quality assurance and control through the life cycle. In this paper the focus is on design, inspection and repair procedures to ensure adequate safety with respect to degradation. While design and inspection criteria in modern codes have been calibrated on a generic basis, particular features of individual structures imply that it is necessary to update the initial inspection plan based on experiences obtained after fabrication and during operation. In this connection fatigue cracks are of special concern. Recent efforts to establish rational, reliability-based procedures for life cycle assessment of fixed offshore platforms are outlined. It is emphasized that the reliability methods should be calibrated to the semi-probabilistic approach that current codes are based on; as well as to operational experiences.