Abstract
When subjective uncertainties are taken into account in structural reliability analysis and subjective evaluations are given in terms of fuzzy sets, we encounter the problem of how to combine a number of evaluations. In this paper, several combination methods used in the field of structural reliability engineering were first examined with respect to the following two points: (i) if the result of combination is independent of order of combination, and (ii) if the result of combination is reasonable when a variety of evaluations are combined. No method examined was found to satisfy both of the conditions. Then, a new combination method was proposed. The method was obtained by modifying Nishimura et al's combination method which was based on Dempster's rule and the concept of vagueness. Modifications were made in treatment of empty sets and vagueness. The method gives the same result independent of the order of combination, and also gives a reasonable result when a variety of evaluations are combined. Furthermore, by using the combination method proposed and preparing five membership functions and three vagueness functions for choice, a way was given for taking account of subjective uncertainties in structural reliability analysis.
