The semi-submersible has been adapted to perform numerous functions offshore unconnected with drilling but still operating as a mobile unit. When used as an early production unit however, it is required to remain on a particular site for several years. The strength and fatigue of one such unit is considered for three different locations in the North Sea. For completeness, several other typical design features have been incorporated into the structure. Existing and proposed fatigue criteria are investigated and the results discussed. The principal conclusion is that major structural modifications will be required if the proposed changes are implemented.

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