Probabilistically Optimum Design of Offshore Platforms with a Minimum Expected Cost Criterion

Abstract

The optimum design pocedure is proposed for offshore platforms minimizing the expected total cost which is composed of the structural cost and the expected maintenance cost. The design variables are the geometrical dimensions of the structure while its configuration and the materials to be used are given. Structural failure is disregarded in the present study since its probability is generally much smaller than the partial failure probabilities and the cost induced by structural failure is difficult to evaluate. The design is performed for the platforms subjected to wave loads. The optimum design problem contains many parameters which are difficult to estimate exactly, and thus the optimum solution may not be absolute. However, the failure probability corresponding to the optimum solution could be used as an index for specifying the allowable failure probability in probabilistically design problem. Numerical examples for a jacket-type offshore platform are provided to illustrate the applicability of the proposed method.