Rick Evaluations for Offshore Structures

While storm damage to offshore platforms can be minimized by the expenditure of money and technical effort, the level of risk to be accepted is properly determined by economic considerations. Relationships between the theoretical and actual strength of elements of offshore platforms—the structural frame and its pile foundation—are presented. These are combined with the uncertainty in applied loads to develop such risk criteria as probability of failure due to a given wave and expected number of failures, which are compared with experience offshore. The effect of hurricane recurrence interval is introduced in terms of the average annual risk rate. The objective of economic evaluation is approached via the criterion of first cost plus deferred risk. Emphasis is on obtaining useable results with a minimum of effort. The numerical and graphical procedures are illustrated with specific examples. Limitations of the method are pointed out.