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CE 3213
REINFORCED CONCRETE
DESIGN
EXAM I – SUMMER 2008
STUDENT NAME
I.
A Tbeam is made of a 4inch thick slab and a web of 14 in x 20 in. It has a span of
24 ft and a tributary width of 16 ft. Determine the effective flange width. (2 points)
¼(24' 12 )=
72"
Controls!
be
= 14+16(4) = 78"
cc: 16' 12= 192"
×⇐
⎧
⎪
⎨
⎪
×
⎩
II.
Recommend the temperature and shrinkage reinforcement for a 12 inch thick slab
(2 points)
The temperature and shrinkage reinforcement varies with the steel yield value. Assuming
f
y
= 60 ksi
As = 0.0018bh = 0.0018(12)(12) = 0.26 in
2
/ft
Using #4 bars (0.20 in
2
):
#4 @ 9”
Using #5 bars (0.31 in
2
): #5@14”
III.
For cold weather concreting, would you use admixtures that are retarders or
admixtures that are accelerators? (2 points)
Accelerators
IV.
List one advantage and one disadvantage of using compression reinforcement (2
points)
Advantage: Ductility
Disadvantage: Deflections
V.
Using the ACI Code and assuming f’
c
= 5000 psi and f
y
= 40,000 psi determine the
ratio of steel (
ρ
) permitted to obtain:
a)
the
smallest
effective size rectangular beam (1 point)
'
1
max
0.85
0.85*0.80*5
0.003
0.036
40
0.003 0.004
cu
yu
t
f
f
βε
ρ
εε
⎛⎞
==
=
⎜⎟
++
⎝⎠
b)
the
largest
effective size rectangular beam (1 point)
min
, since f’
c
> 4440 psi :
'
min
3
3 5000
0.0053
40000
c
y
f
f
=
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 Spring '09
 diaz

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