Civil Engineering Reference
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Unit cost, $
Uncertainty
C
i
Q
i
Quantity
12.3
Example of cost function (Yang
et al.
2009).
Once the total repair quantities are identifi ed, the total repair cost for
the building is computed by multiplying the total repair quantity by the unit
repair cost. Figure 12.3 shows an example of the unit repair cost function.
The uncertainty of the unit price is represented by using a random number
generator, based on the tabulated beta factors for the cost functions, to
adjust base unit costs up or down before multiplying by the total quantities
associated with each repair measure. This is the repair cost for one realiza-
tion of the
EDP
s. The process is repeated a suffi ciently large number of
times to obtain a distribution of total repair costs given the seismic hazard
level. In the methodology adopted here, the performance groups are
assumed to be statistically independent.
Different representations of the total repair cost
Steps 1 through 5 present a logical and consistent methodology that can be
used to obtain a distribution of the total repair cost of a building for one
intensity measure. Figure 12.4 shows an example of such distribution curves
for different intensity measures considered. These curves can be readily
used as a basis for making risk management decisions. For example, the
curve demonstrates the amount of seismic risk increase (in terms of the
total repair cost) as a function of the return period of earthquake ground
shaking. Similar curves can be generated to compare the performance of
different structural framing systems, or different retrofi tting strategies on
the same building.
The repair cost information can be further refi ned by computing the
annual rate of total repair cost exceeding a threshold value. Such annual
rate information is obtained by fi rst computing the complement of the
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