Abstract

In this study, global structural analysis was performed for a semi-submersible drill rig composed of four square columns and twin pontoons connected by transverse wing pontoons. Ultimate limit state (ULS) of the unit was analyzed with LRFD method for operating and survival condition. Operating and survival condition consists of 6 static and 24 dynamic load cases at operating and survival draught, respectively. Design waves through the direct wave load analysis by DNV WADAM were selected for critical structural responses and North Atlantic environmental condition for worldwide operation was considered to find out extreme response values of the unit. Global structural loads were transferred to structural model using DSME in-house system, DSTAS.RIG. The loads were verified through checking the global loads applied to the model. The stress results were combined with applicable load factors for ULS-A and ULS-B, respectively, and then the calculated global stresses were used for the overall hull scantling in view of yielding and buckling. This paper introduces a procedure of global structural analysis for a semi-submersible drill rig in accordance withDNV offshore rules.

Keywords:
boundary condition, pontoon, upstream oil & gas, design wave, semi-submersible drill rig, transfer function, panel model, lrfd method, draught, subsea system
Subjects:
Offshore Facilities and Subsea Systems
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2014. International Society of Offshore and Polar Engineers
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