System reliability of jack-up structures based on fatigue degradation

In recent years there has been considerable development in the area of system reliability assess-ments of offshore structures except for jack-up platform. However, since the reliability of jack-up platform is acrucial aspect with regard to the safety of the structure during its service time and possibly beyond the predictedlifetime, there is significant demand from the offshore industry to investigate system reliability of this type of off-shore structure. This paper therefore presents a methodology to estimate the system reliability of jack-up struc-tures by considering sequence of fatigue failure. First, component reliability of this structure based on fatiguelimit state function is derived, and then the branch and bound technique has been used to identify an importantsequence of section failure leading to system collapse. The structural failure is therefore regarded as the eventat which one of these important sequences occurs. The result determined for a jack-up structure shows a sig-nificant systems effect and that the probability of structural failure is larger than the probability of failure for anindividual section.