Fifteen years after the installation of the Beryl Alpha Condeep platform, a programme to upgrade the topsides facilities was commenced. This upgrading increased the overall design weight of the topsides by some 17%. Due to the modular nature of the additional facilities, weight increases of several hundred tonnes each are applied at discrete points around the deck structure.

Prior to this upgrade, Mobil North Sea Limited (MNSL) had commenced the development of reanalysis models of their structures, including the Beryl Alpha deck. A complete reassessment of the strength of the deck was undertaken using detailed finite element analysis and contemporary code checking methods. The methodology used in the checks combined the application of appropriate codes, recent theory, experimental results and both linear and non-linear buckling analyses. Whereas simpler techniques would have suggested a requirement for considerable stiffening, this methodology demonstrated that even the substantial additional loads from the upgrade could be carried with only minor and localised strengthening being required.

This paper discusses the methods used together with the approach adopted for the design of stiffening at minimal cost.

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