Deck 23: Concrete Construction-II Site-Cast and Precast Concrete Framing Systems

Question 1

The primary reason for using posttensioned concrete floors is to

A)reduce formwork cost.
B)reduce or prevent the cracking of concrete.
C)reduce floor depth.
D)reduce or prevent corrosion of reinforcement.
E)improve safety against failure.

Answer 1

C

Question 2

Portland cement used in precast concrete members is generally

A)Type I.
B)Type V.
C)Type III.
D)Type IV.
E)Type II.

Answer 2

C

Question 3

The strength of concrete used in precast concrete members is generally

A)1 ksi to 2 ksi.
B)2 ksi to 3 ksi.
C)3 ksi to 4 ksi.
D)4 ksi to 5 ksi.
E)5 ksi to 6 ksi.

Answer 3

E

Question 4

In a one- way joist floor, the supporting beams run in one direction and the joists run in the other direction. If the spans in the two directions are unequal, the beams should preferably span along the

A)shorter direction.
B)longer direction.

Question 5

A band beam floor is generally more economical than a beam- and- girder floor because

A)it requires a smaller quantity of reinforcement.
B)it requires a smaller quantity of concrete.
C)its formwork is more economical.
D)none of the above.

Question 6

The formwork used for a waffle slab has

A)a dome profile.
B)a U- shaped profile.
C)a Z- shaped profile.
D)any one of the above.
E)none of the above.

Question 7

Commonly used beamless concrete floors are

A)beam- and- girder floors.
B)flat- plate and flat- slab floors.
C)one- way and two- way joist floors.
D)all of the above.

Question 8

A reinforced- concrete, four- side- supported slab panel measuring 15 ft × 32 ft is

A)a one- way slab.
B)a two- way slab.
C)a four- way slab.
D)A or B.
E)none of the above.

Question 9

Pans used as formwork for one- way joist floors have

A)a dome profile.
B)a Z- shaped profile.
C)a U- shaped profile.
D)any one of the above.
E)none of the above.

Question 10

A standard- module one- way joist floor is constructed using pans that are

A)20 in. wide.
B)30 in. wide.
C)40 in. wide.
D)A or B.
E)B or C.

Question 11

Architectural precast concrete refers to concrete members used in building interiors.

Question 12

A reinforced- concrete, four- side- supported slab panel measuring 15 ft × 22 ft is

A)a one- way slab.
B)a two- way slab.
C)a four- way slab.
D)A or B.
E)none of the above.

Question 13

Based on structural considerations only, the thickness of the slab in a standard- module one- way joist floor need not exceed

A)4 in. to 5 in.
B)3 in. to 3- 1/2 in.
C)5 in. to 6 in.
D)2 in. to 2- 1/2 in.

Question 14

Using standard formwork components for a waffle slab, the center- to- center distance between waffles (voids)is

A)4 ft, 5 ft, or 6 ft.
B)5 ft, 6 ft, or 7 ft.
C)3 ft, 4 ft, or 5 ft.
D)2 ft, 4 ft, or 6 ft.
E)none of the above.

Question 15

A reinforced concrete, four- side- supported slab panel is

A)a one- way slab.
B)a two- way slab.
C)a four- way slab.
D)A or B.
E)B or C.

Question 16

A flat plate floor consists of

A)a slab with drop panels at each column.
B)a slab of constant thickness.
C)a slab with beams on all four sides of the slab panel.
D)none of the above.

Question 17

A flat slab floor consists of

A)a slab with beams on all four sides of the slab panel.
B)a slab with drop panels at each column.
C)a slab of constant thickness.
D)none of the above.

Question 18

In a posttensioned elevated concrete floor, prestressing tendons are combined with conventional steel reinforcement.

Question 19

In a band beam reinforced- concrete floor, the beams are

A)located at a spacing of 8 ft to 10 ft on center.
B)wide and shallow.
C)narrow and deep.
D)unnecessary.

Question 20

A wide- module one- way joist floor is constructed using pans that are

A)53 in. wide.
B)60 in. wide.
C)66 in. wide.
D)A or B.
E)A or C.

Question 21

In total precast construction, precast concrete members are generally used for

A)columns.
B)floors.
C)shear walls.
D)load- bearing walls.
E)all of the above.

Question 22

In this text, elevated concrete floors have been divided into: (i)beam- supported floors and (ii)beamless floors. Explain the difference between them.

Question 23

What is the center- to- center spacing of joists in standard- module, one- way joist floors?

Question 24

What is the width of pans in standard- module, one- way joist floors?

Question 25

A 12- in.- thick hollow- core floor slab will generally span up to approximately

A)20 ft.
B)30 ft.
C)40 ft.
D)25 ft.
E)none of the above.

Question 26

The most commonly used width of a double- tee floor unit is

A)8 ft.
B)4 ft.
C)6 ft.
D)none of the above.

Question 27

A reinforced concrete floor is framed with beams spaced 30 ft on center in one direction and 20 ft on center in the other direction. Are the slabs that span between the beams one- way slabs or two- way slabs, or does the floor have a combination of these two? Give reason(s)for your answer.

Question 28

A reinforced concrete floor is framed with beams spaced 35 ft on center in one direction and 16 ft on center in the other direction. Are the slabs that span between the beams one- way slabs or two- way slabs, or does the floor have a combination of these two? Give reason(s)for your answer.

Question 29

Double- tee floors are commonly used

A)where spans lie between 40 ft and 50 ft.
B)where spans are in excess of 50 ft.
C)in residential occupancies.
D)where spans lie between 30 ft and 40 ft.

Question 30

The fire- resistance rating of concrete members is a function of

A)concrete cover for corrosion protection.
B)type of coarse aggregate in concrete.
C)member thickness.
D)all of the above.

Question 31

Indicate which of the following concrete floors are beam- supported floors and which are beamless floors. One- way slab floor
Flat- plate floor Flat slab floor
Two- way slab floor One- way joist floor

Question 32

Explain the difference between a concrete slab- on- ground and an elevated concrete slab.

Question 33

When a concrete topping is used over hollow- core slabs, its thickness is approximately

A)1 in.
B)3 in.
C)2 in.
D)4 in.
E)1- 1/2 in.

Question 34

In mixed precast construction, precast concrete members are generally used for

A)columns.
B)load- bearing walls.
C)floors.
D)shear walls.
E)all of the above.

Question 35

What is the cross- sectional shape of pans in one- way concrete joist floor system?

Question 36

The purpose of concrete topping on hollow- core slabs is to

A)increase the fire rating of the floor.
B)structurally integrate the slabs.
C)increase the sound insulation of the floor.
D)level the top of slabs.
E)all of the above.

Question 37

Which of the two one- way joist floor systems-standard module or wide module-is more common in contemporary concrete construction and why?

Question 38

One- way concrete joist floors can either be standard- module, one- way joist floors or wide- module, one- way joist floors. Which of these two was introduced first?

Question 39

What is the center- to- center spacing of joists in wide- module, one- way joist floors?

Question 40

What is the width of pans in standard- module, one- way joist floors?

Question 41

Which floor system-one- way joist floor or two- way joist floor-is more commonly used in contemporary concrete construction and why?

Question 42

Using sketches, explain the commonly used beamless concrete floor systems.

Question 43

The posttensioning of elevated concrete floors reduces the slab and beam dimensions. This reduces the cost of concrete and reinforcing bars but is compensated for by the added cost of posttensioning steel and the use of more skilled (posttensioning)labor. So, why is posttensioning of concrete structures so popular.

Question 44

A flat- plate or a flat- slab floor is a beamless concrete floor. However, in many situations, such floor slabs are often provided with shallow perimeter beams. What is that in response to?

Question 45

Name two commonly used precast concrete elements used as structural floors.

Question 46

What is the difference between structural precast concrete and architectural precast concrete?

Question 47

What is the other commonly used term for a two- way joist floor?

Question 48

In which situations are inverted- tee beams used?

Question 49

Explain the difference between total precast and a mixed precast construction.

Question 50

Concrete construction can either be done as cast- in- place concrete or precast concrete. Give three disadvantages of precast concrete.

Question 51

Concrete construction can either be done as cast- in- place concrete or precast concrete. Give three advantages of precast concrete.

Question 52

What is the difference between a flat plate concrete floor and a flat slab concrete floor?

Question 53

What is the cross- sectional shape of pans in a two- way concrete joist floor system?

Question 54

Sketch the following precast concrete structural members:
a. Hollow- core units
b. Solid planks
c. Double- tee units
d. Inverted- tee beams

Question 55

Name the factors that affect the fire resistance of reinforced or prestressed concrete members.

Question 56

In the case of a one- way joist floor system, the joists span in one direction and the beams span in the other (perpendicular)direction. If the two spans are unequal, in which direction (shorter or longer)should the beams span and why?

Question 57

Using sketches and notes, illustrate the two most commonly used reinforced- concrete floor systems.

Question 58

Using sketches and notes, explain beam- and- girder floor systems.

Question 59

Why is the one- way joist floor a popular structural system in concrete construction?

Question 60

Explain the difference between one- way slab and two- way slab actions.