Reliability Analysis of Leg Mating Unit under Impact Loads Due To Floatover Installation

Regarding Iran's need to increase its current oilfields production, especially in the South Pars field and decommissioning new fields, it is a necessity to fully understand and comprehend the Floatover installation method as a cost-effective and reliable method and as an alternative for traditional lifting method. This method is complex and demands the study of all environmental parameters and elements involved. All of these parameters contain uncertainty. This study examines the environmental uncertainties and uncertainty in steel by comparing leg mating units and using Taguchi design and response surface methods. A model including a jacket, topside, and a barge with 6 degrees of freedom was developed to assess hydrodynamic analysis in the Persian Gulf. Then, using the Taguchi design and the Box-Behnken method, and by monitoring the maximum Von Mises stress, the explicit limit state function was generated. This stress was calculated using a finite element model that represents impacts and interactions. By creating two limit state functions, a reliability analysis was performed. In these functions, the effect of environmental parameters on the failure of the leg mating units was investigated.  Finally, the effect of environmental uncertainties and the yielding stress of steel in the Floatover method were evaluated using FORM and SORM methods and Monte Carlo simulation. It was concluded that uncertainties in steel and some of the environmental parameters have a significant impact on failure.