The Fatigue Analysis Of Jack-up Platform Jacking System

Ocean platform must withstand extremely complex load in service period, often withstands the high-frequency alternating load, but the elevating gear already needs to complete the spud leg and the deck fluctuation under the fluctuation condition, and also needs sustaining hull deck and equipment in the normal work condition and the storm. The Shelf of fixup-leg is a important constituent of jack-up platform jacking system. Shelf of fixup-leg took the connection spud leg and the platform main body main structure, moves the platform in the jack up under each kind of work condition to play the transmission load role. So there is more possibility that shelf of fixup-leg appears to be fatigue failure. Failure analysis of shelf of fixup-leg is very necessary.First, integral special shell-beam element model of shengli3 is set up, which has been carried on the static analysis to it under the extreme wave condition. Besides , static strength of the platform host hull structure and the spud leg are checked according to the structural strength and the standard.Then, the platform has been carried on the modality analysis and the dynamic response analysis. Through the modality analysis we can see oscillation characteristic of the platform; also we can get stress-time response of shelf of fixup-leg through the platform dynamic response analysis. Thus we can determination hazard point, as well as stress-time response of hazard point.Finally, through analysis and disposed of stress-time response of hazard point of shelf of fixup-leg , used the P-S-N curve method and the linearity cumulative damage theory has carried on the computation to the platform structure fatigue damage, and appraised platform structure fatigue life. The method and computed result has certain guiding sense to the platform life estimate.