Fuzzy Fault Tree Analysis of Crane Wire Rope

Wire rope is a very useful and long lasting structural element when properly used and maintained. For a failure such as that of crane wire rope, it is often very difficult to estimate precise failure rates or failure probabilities of individual components or failure events. Conventional fault tree analysis (FTA) is based on the probability assumption. When the failure probability of a system is extremely small or necessary statistical data from the system is scarce, it is very difficult or impossible to evaluate its reliability and safety with conventional fault tree analysis (FTA) techniques. To overcome this disadvantage, fuzzy sets theory is introduced. The reliability of basic events is considered as R L − type fuzzy numbers with weighted exponents. A weighted exponent represents the assuring measure of the decision-maker to the membership functions of basic events. From the logical relationship between different events in the fault tree and fuzzy operators AND and OR, the fuzzy probability of the top event is obtained. Finally, fuzzy fault tree analysis of crane wire rope is given to illustrate the proposed method.