A random-fuzzy analysis of existing structures

Two approaches are proposed to estimate the reliability of existing structures by considering both the randomness in some of the design parameters and the fuzzy imprecision in some other parameters representing the in-place condition of the aged structures. In the first approach, the fuzzy imprecision is transformed into random uncertainty using the entropy concept, and the reliability of existing structures is estimated using well-established theories of probability. In the second approach, a hybrid approach in the random-fuzzy domain is used to evaluate the reliability using an α-level concept. The multiple fuzzy variables case is also considered. Both discrete and continuous fuzzy variables are considered. The results obtained from the proposed approaches are compared with other techniques available in the literature whenever possible. Both methods are applied to civil structural engineering problems in this paper. The results obtained are very encouraging and demonstrate the applicability and robustness of the algorithms.