6-27.
Of the following descriptions, which
most accurately describes
pretensioning of concrete members?
1.
After the concrete has been
placed and has reached a
specified strength,
reinforcement strands are pulled
through formed channels, and a
predetermined amount of stress
is applied
2.
Reinforcement strands are pulled
through inflated tubes and are
stressed before placement of the
concrete
3.
Reinforcement strands are
stressed to a predetermined
point before placement of the
concrete and are released just
before the concrete has set
4.
Reinforcement strands are placed
in the forms and are stressed to
a predetermined point before the
concrete is placed; the strands
are then released after the
concrete has reached a specified
strength
6-28.
In what part of a prestressed beam
does the tensioned steel produce
high compression?
1.
Upper
2.
Lower
3.
Exact center
4.
Approximate center
6-29.
What condition occurs when a load
(force) is placed on a prestressed
beam?
1.
The camber is forced out,
leaving a beam with positive
deflection
2.
The upward bow is increased
3.
The camber is forced out,
leaving a level beam with no
deflection
4.
The upward bow is forced out,
creating deflection in the beam
6-30.
What is the approximate weight of
conventional concrete?
1.
175 lb/cu ft
2.
150 lb/cu ft
3.
130 lb/cu ft
4.
115 lb/cu ft
IN ANSWERING QUESTIONS 6-31 THROUGH 6-35,
SELECT THE TYPE OF CONCRETE FROM THE
FOLLOWING LIST THAT BEST MATCHES THE
CHARACTERISTIC GIVEN.
A.
HEAVYWEIGHT CONCRETE
B.
SEMI-LIGHTWEIGHT CONCRETE
C.
INSULATING LIGHTWEIGHT CONCRETE
D.
STRUCTUTWL LIGHTWEIGHT CONCRETE
6-31.
Weighs 115 to 140 lb/cu ft and has a
compressive strength comparable to
normal concrete.
1. A
2. B
3. C
4. D
6-32.
Weighs 20 to 70 lb/cu ft and is used
for fireproofing.
1. A
2. B
3. C
4. D
6-33.
Weighs up to 400 lb/cu ft.
1. A
2. B
3. C
4. D
6-34.
Weighs up to 115 lb/cu ft and is
used to decrease the dead-load
weight of structural members.
1. A
2. B
3. C
4. D
6-35.
Normally has a compressive strength
of 1,000 psi or less.
1. A
2. B
3. C
4. D
6-36.
In what type of construction are
concrete walls poured horizontally,
lifted upright, and then secured in
place?
1.
Tilt-up
2.
Lift-up
3.
Cast-in-place
4.
Prefab
6-37.
In tilt-up panel construction, where
is additional reinforcement
generally needed?
1.
At the top
2.
At the bottom
3.
Around the edges
4.
Around any openings
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