A Multi-Hazard Framework for Optimum Life-Cycle Cost Design of Reinforced Concrete Bridges - Structural Seismic Design Optimization and Earthquake Engineering - page 99

Figure 15. Ratio of total failure cost to initial
construction cost for three levels of seismic hazard
risk (Note: The geometric characteristics of each
bridge case number can be found in Table 3):
(a) low seismic hazard risk; (b) medium seismic
hazard risk; (c) high seismic hazard risk

Table 8. Values assumed for b f and t f at different
damage states

Damage State b f t f

slight 0 0

moderate 0.25 1 month

extensive 0.50 6 months

complete 1.00 24 months

point, the ratio of total failure cost increases be-
tween 5% to 19% for various bridge cases as the
inspection and maintenance interval changes from
every 1 year to every 5 years. On the other hand,
planning for more frequent inspection and main-
tenance intervals may cause an increase in the
total life-cycle cost of a bridge. Selecting the
two-span bridge with the medium span length and
column height of 10.0 m as the case-study, it is
found that the ratio of total life-cycle cost (LCC)
to initial construction cost is equal to 2.7, 2.4, and
3.3 for the inspection and maintenance intervals
of 1, 2, and 3 years, respectively. This indicates
that a 2-year interval would be probably an opti-
mized interval which saves more money while
limiting the probability of bridge failure.
As discussed earlier, the current chapter pro-
vides a multi-hazard framework for the estimation
of the total life-cycle cost of bridges. But one may
question the importance of the proposed frame-
work considering the efforts required to take into
account the deterioration process in addition to
the seismic hazard risk. To respond to this concern,
a comparison has been made between the ratios
of total failure cost to initial construction cost
calculated with and without the effects of the
corrosion process (Figure 16). It can be found that
this ratio is underestimated by a factor of 47% on
average in case that the corrosion process is ig-
nored. This indicates that the accuracy of life-
cycle cost estimations can be improved signifi-
cantly through the developed framework.
In order to simplify the evaluation of the cor-
rosion process and easily incorporate it into the