Detailed Fatigue Analysis for Jackets in Shallow Waters of Bohai Bay

摘要

Because in shallow water it is uncommon for jacket platforms to havefatigue problems, the simplified fatigue analysis can be used instead ofdetailed fatigue analysis under some conditions which have beendefined in many related international standards, for example API.However, according to the results of detailed fatigue analysis forshallow water jackets with relatively large natural period, we find thatthe fatigue life of some joints may not satisfy the design requirementseven though they can satisfy the simplified fatigue analysis conditions.In order to make clear the reason, in this paper some design propertiesof these jackets are discussed such as design water depth, naturalvibration period, conditions for simplified fatigue analysis and yearlyprobability of wave occurrence. Finally we find that when the naturalvibration period of these jackets is close to the wave period, resonancewhich can cause fatigue problem of tubular joints usually occursbetween the jackets and wave. So if you don't have enough confidence,detailed fatigue analysis should not be replaced, although thesereplacements may accord with some international standard.