A new method for fuzzy fault tree analysis

It is well-known that the conventional fault tree analysis using probabilities has been found to be inadequate to handle the imprecision of input failure data and the uncertainties associated with the modelling particularly in relation to dependency of failures. Therefore, to overcome these problems, a Fuzzy Fault Tree Analysis (FFTA) based on possibility distributions associated with the basic events and a fuzzy algebra for combining these events, has been presented in this paper. The authors propose an algorithm based on a discretization procedure which permits consideration of any arbitrary possiblity distribution for the events and provides a higher precision than that could be obtained in a graphical approach, as is presented here. The method described in this paper can be used for any coherent system. Further, an approximate representation for conditional possibility distributions has also been provided which can be used in conjunction with AND and OR-gates of the fault tree to consider the dependency of failures