Uncertainties exist at practically all stages of the design and construction process because of incomplete knowledge. Extreme environmental forces on offshore structures are uncertain because of the stochastic nature of the underlying physical phenomena. The actual strength and fatigue characteristics of structures can be predicted only approximately at the design stage and these predictions can be refined only partially by compliance tests during and after fabrication, and then only at high cost.

The boundary element method is combined with the method of compatible deformations to obtain stress intensity factors for a cracked sheet reinforced with a repair patch. The method is applied to the analysis of a circular patch over a central crack in a rectangular uniaxially stressed sheet. It is shown that the proximity of the edges of the sheet to the patch edge has a negligible effect on the stress intensity factor of a crack completely under the patch.

This paper presents a review of the current status and potential future use of reliability methods in the design, fabrication and operation of offshore oil production platforms.

An overview of the traditional design process is presented and key areas where reliability methods have contributed to the development of codes of practice are described. Future applications in the design stage include the optimisation of framing configurations and the treatment of uncertainties in basic design parameters.