Global Structural Analysis for Semi-submersible Drill Rig

摘要

In this study, global structural analysis was performed for a semisubmersibledrill rig composed of four square columns and twinpontoons connected by transverse wing pontoons. Ultimate limit state(ULS) of the unit was analyzed with LRFD method for operating andsurvival condition. Operating and survival condition consists of 6 staticand 24 dynamic load cases at operating and survival draught,respectively. Design waves through the direct wave load analysis byDNV WADAM were selected for critical structural responses andNorth Atlantic environmental condition for worldwide operation wasconsidered to find out extreme response values of the unit. Globalstructural loads were transferred to structural model using DSME inhousesystem, DSTAS.RIG. The loads were verified through checkingthe global loads applied to the model. The stress results were combinedwith applicable load factors for ULS-A and ULS-B, respectively, andthen the calculated global stresses were used for the overall hullscantling in view of yielding and buckling. This paper introduces aprocedure of global structural analysis for a semi-submersible drill rigin accordance with DNV offshore rules.