Table 8-19. Design history of RBDO based on sequential deterministic optimization
using probabilistic sufficiency factor to correct safety factor directly by
Equation (8-3)
Safety Minimize obj ective function W while pof <0. 0001
factor for Obj ective PoflPSF from Critical strength
strength [b, h, t,, 81, tz, 82] function: MCS of 106 failure mode
failure mode weight (lb) samples* (load case 1)
Initial [9.999, 1.583,.
design 0.02229, 87.57, 3386 .008978/0.837178 Iordi-ln
3 shear
(s =1.2) 0.0395, 14.84]
S = [9.997, 0.9701,
Skin transverse-
s /0.837178 0.01828, 89.54, 3192 0.00000/1.179381
=1.437514 0.07011, 0.1484] esl
S3 [9.997, 0.8254,
Skin transverse-
s2/1.179381 0.005205, 90.00, 1878 0.001875/0.944237
tensile
=1.218872 0.07087, 0.9826]
pof = probability of failure, PSF = probabilistic sufficiency factor
Table 8-20. Design history of RBDO based on sequential deterministic optimization
using probabilistic sufficiency factor to correct safety factor by actual safety
margin using Equation (8-4)
Safety Minimize obj ective function W while pof <0. 0001
factor for Obj ective PoflPSF from Critical strength
strength [b, h, t,, 81, tz, 87] function: MCS of 106 failure mode
failure mode weight (lb) samples (load case 1)
Initial [9.999, 1.583,.
Isogrid in-plane
design 0.02229, 87.57, 3386 0.008978/0.837178
(s =1.2) 0.0395, 14.84]~ ha
S2= [9.997, 0.9701,
Skin transverse-
s /0.837178 0.01828, 89.54, 3192 0.00000/1.179381
=1.437514 0.07011, 0.1484] esl
S3= [9.997, 1.137,
s2/1.7938lSkin transverse-
s21.79810.006349, 90.00, 2058 0.000080/1.002482
tensile
=1.218872 0.05445, 0.001495]
pof = probability of failure, PSF = probabilistic sufficiency factor
It is seen that the third designs in Table 8-19 and quite different from that in Table
8-20, because the different correction formulation used. The designs in Table 8-19 use
direct correction to the safety factors employed in the previous design iteration shown by
Equation (8-3), while designs in Table 8-20 employed correction to the actual safety
margins of the previous design iteration shown by Equation (8-4). Comparing the third