The safety assessment of existing platform is a complicated decision process, which depends upon many factors of uncertainty. The fuzzy Analytic Hierarchy Process Method (FAHP) Is presented in this paper for modeling and solving the problem. Detail information are given and the development is based on the fuzzy mathematics and the artificial intelligence techniques as well. Practical example is shown for the purpose of illustrating the strategy. Further development of combination the "soft" science to the "hard" engineering can potentially be seen.
The collapse of offshore jacket is caused by successive damage of its components, characterized by a series of damage stage. The jacket structure will collapse until the structural integrity finally vanishes, while the structure behaves as a kinematic mechanism and approaches to its ultimate state, on which founds the theoretical basis of safety assessment of the structure. Above mentioned situation is much realistic, on the one hand, it is becoming increasingly necessary to re-assess the adequacy of existing platforms in safety, which were built in 60s or 70s; on the other hand, since the cost of open sea engineering work is extremely expensive, one would rather avoid to take a capital repair for reinforcing a damaged platform instead of taking more precise estimation of the residual strength of the structure based on more reasonable safety assessment. The objective of safety assessment of to establish a criterion of whether the existing structure can safely perform its function. Along this line, the problem is how to realize this acceptable, though it is indeterministic or fuzzy, criterion for safety assessment The safety assessment is related to the quantitative evaluation of defaults or damages in individual member as well as to its influence to the carrying capacity of the structure.
