Project-network analysis using fuzzy sets theory

Estimating the durations of construction activities requires experts knowledge. Statements used by these experts usually contain some sort of imprecision. Previous studies have demonstrated the use of fuzzy set theory for quantifying the imprecision associated with the durations of project activities. These studies, however, did not address the processing of this information for generating a complete schedule. This paper presents a new network scheduling method based on fuzzy sets theory. The proposed method incorporates a number of new techniques that facilitate: (1) the representation of imprecise activity durations; (2) the calculation of scheduling parameters; and (3) the interpretation of the fuzzy results generated. Two network examples are worked out to illustrate the use of the proposed method, and to compare its capabilities with Monte Carlo simulation. The results indicate that the proposed method is capable of providing schedules that can appropriately account for the nature as well as the type of uncertainties normally encountered in construction projects. The results are in close agreement with those obtained using Monte Carlo simulation. The calculations are, however, more simple, requiring less computational effort than that needed in Monte Carlo simulation. The proposed method is practical and can be easily computerized.