Computing a Model for Asset Management with Risk - Global Drinking Water Management and Conservation - page 180

Fig. 8.10 The service cost of
this asset is minimized if it is
renewed at approximately
every 20 - 35 years

Fig. 8.11 Iterative
adjustment reveals that the
precise solution is 26.65 years

fitted to the data shown in Figs. 8.12 and 8.3 to
demonstrate initial slow growth that increases, and then slows again. The carrying
capacity for the failure is set at 2,250 and the initial value is set at 10. Experi-
menting with different growth rates yields an ideal growth rate for this application
of 0.21. Figure 8.14 demonstrates this.
The frequency of failure seems to have a carrying capacity of 25 and the initial
value is again set low, this time at 0.01. Adjusting the growth rate to ensure that
the curve

As in City A, logistic curves are

fits the data yields a growth rate of 0.32. This function is depicted in
Fig. 8.15 . Utilizing these two new functions for cost and frequency yields
Eq. 8.10 .