Reliability Based Inspection Planning of Fatigue Damaged Offshore Platforms

Authors

Michael H. Faber

Abstract

The present paper summarizes the results of research and development efforts over the last five years to develop simplified and practically applicable approaches for reliability and risk based inspection planning. These efforts have led to the development of a generic approach for inspection and maintenance planning. Following the approach the fatigue sensitive details are categorized and described generically according to standard design parameters such as the Fatigue Design Factor (FDF) and the SN curve. When a measure of the structural consequences of fatigue failure e.g. the RSR and the corresponding probability of structural collapse given fatigue failure of the considered detail are known, generic inspection plans may derived as a function of the generic parameters together with the relative cost of inspections, repairs and failures. Due to the simplicity of the format of the developed inspection plans, the proposed approach has a high potential to be used in codes for the design and maintenance of steel structures.

The validity of the proposed approach is illustrated through a study regarding inspection planning of a tri-pod offshore structure where generic inspection plans are obtained using two approximations, namely assuming equidistant inspection intervals and using constant thresholds for the annual probability of failure. Results obtained using the simplified and generic approach are compared and found in good agreement with results obtained when solving the general solution of the inspection and maintenance-planning problem.

Published in/by

Proceedings to the International PEP-IMP Symposium on Risk and Reliability Assessment for Offshore Structures, Mexico City, Mexico, December 3-4, 2001.