For general reliability analysis with fuzzy failure region F % , the general failure
probability F P% is defined as the integral of product of μF% [g( y)] , the membership of performance
function ( ) g y to F % , and joint Probability Density Function (PDF) f ( y) over , the total
variable space, i.e. [ ( )] ( ) F F P μ g f d % = ∫ ∫ % y y y L . On the basis of line sampling, an efficient method
for random failure probability analysis with clear failure region, a new numerical method is
presented to calculate F P% . In the presented method, the total integral region is split into m clear
sub-regions i F in a way that the value of g( y) in i F can be approximately viewed as i g , a
constant independent of y , and the value of [ ( )] F μ % g y in i F can be viewed as a constant
( ) F i μ g % subsequently. Due to the closely invariant property of [ ( )] F μ g % x in i F and
1 2 m = F I F ILI F , F P% is transformed into the sum of ( ) F i μ g % ( )
i F ∫L∫ f y dy , where
( )
i F ∫L∫ f y dy is the random failure probability with the clear failure region i F and can be
obtained by line sampling. The high efficiency of the presented method resulted from that of the
line sampling is demonstrated by the illustration.