System reliability of a semi-submersible drilling rig

This paper deals with system reliability of a typical semi-submersible drilling rig, which is composed of spatial membrane elements and subjected to combined static loads and extreme wave loads. Firstly, methods for reliability analysis of structures are discussed and the concentration is on system reliability of offshore structures, especially for semi-submersible platforms and the like. The whole semi-submersible structure may be considered as a series system and system reliability theory will be applied by calculation of these structural members. Failure conditions of these equivalent components are introduced which take into account the yielding collapse under extreme characteristic wave conditions. Finally, the discussed method is applied to a semi-submersible drilling rig under characteristic hydrodynamic load conditions. Through comparison between numerical examples and others results using simple structure models, the applicability of the proposed method is demonstrated. The reliability analysis of semi-submersible will hopefully promote reliability theory application on offshore engineering field and practical design of semi-submersible and other floating structure systems.