Experts’ Judgment-Based Mamdani-Type Decision System for Risk Assessment

Table 1

Fuzzy sets for risk likelihood and risk severity.

Variable	Parameter	Description	Fuzzy numbers
Risk likelihood	Improbable (I)	Probability of risk to occur is very low	(0, 0, 3)
	Remote (R)	Probability to occur is relatively low	(1, 3, 5)
	Occasional (O)	Sometimes	(3, 5, 7)
	Probable (P)	High	(5, 7, 9)
	Frequent (F)	Probability to occur is almost certain	(7, 10, 10)
Risk severity	Negligible (N)	There is no delay or damage occured	(0, 0, 3)
	Minor (M)	Delay is relatively low and less damaged	(1, 3, 5)
	Serious (S)	Delay/damage occurred	(3, 5, 7)
	Critical (C)	Major delay and damage occurred	(5, 7, 9)
	Catasthropic (Ca)	Project failure	(7, 10, 10)
Risk criteria	Tolerable (T)	Insignificant risk	(0, 0, 3)
	Low (L)	Risk is acceptable	(1, 3, 5)
	Medium (M)	Risk is moderately acceptable	(3, 5, 7)
	High (H)	Risk is significant	(5, 7, 9)
	Intolerable (IN)	Risk is not acceptable	(7, 10, 10)

RL, RS, and the underlying output RC are interpreted in the triangular MFS, as shown in Figure 4 as adopted from Carr and Tah [31], where Improbable (I) = (0, 0, 3), Remote (R) = (1, 3, 5), Occasional (O) = (3, 5, 7), Probable (P) = (5, 7, 9), and Frequent (F) = (7, 10, 10). On the contrary, experts also provide the numerical scale of RC in percentages.