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CE 3213
REINFORCED CONCRETE
DESIGN
EXAM I – SPRING 2008
STUDENT NAME
I.
What is the
minimum amount of
f’
c
for the concrete to be considered structural as defined by the ACI
Code.? (2 points)
The minimum value is 2,500 psi
II.
What is the
Whitney Compression Block
? (2 points)
It is an equivalent rectangular compressive stress distribution. It uses an average stress of
'
0.85
c
f
uniformly distributed over an equivalent compression zone bounded by edges of the cross section
and a straight line located parallel to the neutral axis at a distance
1
β
=
ac
from the fiber of
maximum compression strain.
III.
Give at least two cases where the use of a superplasticizer is recommended? (2 points)
For pumping concrete
To produce highstrength concrete with w/c ratio of about 0.35
In areas where vibration of the concrete is difficult
IV.
Using the ACI Code and assuming f’
c
= 3000 psi and f
y
= 60,000 psi determine the steel
area permitted to
obtain:
a)
the
largest
effective size rectangular beam (1 point)
'
min
3
3 3000
0.0027
60,000
200
200
0.0033
60,000
c
y
y
f
f
f
ρ
⎧⎫
⎪⎪
==
≥
⎨⎬
⎩⎭
min
0.0033
=
b)
the
smallest
effective size rectangular beam (1 point)
'
0.85
0.85*0.85*3.0
0.003
1
0.0155
max
60
0.004
min
βε
εε
⎛⎞
⎜⎟
=
++
⎝⎠
f
cu
f
yu
t
V. What is the difference between
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 Spring '09
 diaz

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