S

Figure 36.13 (Estes et al. 2004) shows the prior, inspection, and posterior distributions for the corrosion loss in both the splash zone and the atmospheric zone. Because of the high degree of corrosion expected in the splash zone and its associated uncertainty, the inspection results dominated the posterior distribution. The projected deterioration and its uncertainty were much less in the atmospheric zone. The deterioration model and the inspection results received about equal weight in computing the posterior distribution. Estes et al. (2002, 2004) provide a complete description of this example.

Corrosion thickness loss, |m

Corrosion thickness loss, |m

FIGURE 36.13 Bayesian updating based on inspection results for the atmospheric and splash zones on a corroding miter gate. (Estes et al. 2004. Reprinted with permission from Elsevier.)

Corrosion thickness loss, |m

FIGURE 36.13 Bayesian updating based on inspection results for the atmospheric and splash zones on a corroding miter gate. (Estes et al. 2004. Reprinted with permission from Elsevier.)

36.8 Maintenance and Repair

Maintenance and repair are actions taken to slow a structure's rate of deterioration, improve its performance, and lengthen its useful life. The options range from preventive maintenance to partial repairs to replacement of major components. For each option, the analyst needs to know the cost of the remediation and its positive effect on the safety of the structure. Based on the answer, the analyst needs to optimize the timing of the maintenance action and compare its benefits to other available options. The situation will be different for every type of structure and deterioration.

The problem is illustrated conceptually in Figure 36.14 (Frangopol et al. 2001c), where under ideal conditions, a structure would perform as intended without maintenance throughout its useful life.

FIGURE 36.14 The effect of various types of maintenance on a typical structure. (Frangopol et al. 2001c. Reprinted with permission from the International Association for Bridge and Structural Engineering.)
TABLE 36.7 Description of the Random Variables Incorporated into an Analysis of the Effects of Preventive Maintenance

Variable

Description

bo

Initial reliability index

ti

Time of damage initiation

a

Performance deterioration rate without maintenance

g

Immediate improvement in reliability index after the application of preventive maintenance

tR

Rehabilitation time (i.e., time at which the minimum acceptable reliability level is

0 0

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