Earthquake Engineering Research - HKU Libraries - The University ...

278
160,000 -
140,000
_^
d Concrete
• Form works
120,000 - -j DRebars
!
1
1
"
"
100,000 -
s :
60,000 -
40,000
—
—
-
1
-
20,000
n
FIGURE 2
COST OF THE DIFFERENT COMPONENTS OF THE STRUCTURES
As a group, the structures designed using the equivalent stiffness criterion (NSO-N120) show an
increase in the cost of the concrete component as the strength of the material increases. The cost of the
formwork remains relatively stable. The cost of the steel reinforcement is almost similar among the
high strength concrete structures and is substantially less than that of the normal strength concrete
structure. The group designed using the reduced stiffness criterion seems to be the most economical.
The cost of the concrete component increases with increasing concrete strength, but is generally less
than the normal strength concrete structure. The cost of formwork (as in the previous group) remains
relatively the same, while the cost of the steel component shows a slight increase with increasing
concrete strength. The structures using only one grade of steel appear to be the least economically
viable. The relative savings over T expenditures are given in Table 4.
Model
% Savings
N35
0.00%
TABLE 4
PERCENTAGE SAVINGS RELATIVE TO N35
N80
8 08%
N100
5.35%
N120
-0.99%
N80R
17.70%
N100R
12.99%
N120R
6 57%
N80RS N100RS
11.85% 6.22%
N120RS
-1.14%
At this cost level, it is noticeable that even the structures using only one grade of steel become
economically feasible. Moreover, the use of high strength concrete can result in substantial savings.
This suggests that the cost effectiveness of a high strength structure depends to a large extent on the
cost component attributable to the steel reinforcement. As this item drops due to wider international
use, high strength RC buildings will become more economical than has hitherto been the case.