CONCRETE STRUCTURES

Multiple-Choice:

Clearly mark only one correct answer for each question:

Each correct answer is worth 4 points

1. What is the optimum concrete floor system for a 48'-0" two way span? ( 4 points)

a. 2-way Beam and Slab

b. Precast Planks

c. Flat Plate

d. x Waffle Slab

2. If a slab is allowed to bends in two direction, it is classified as? ( 4 points)

a. plate

b. one-way slab

c. x two-way slab

d. structurally undefined system

3. Temperature steel is placed in a slab (4 points)

a. diagonal to the stirrups

b. x perpendicular to the flexural steel

c. vertical to the main reinforcement

d. hexagonal to the main steel

4. A slab which is continuous over several supports must be analyzed as? ( 4 points)

a. x continuous beam 1'-0" wide

b. continuous column

c. continuous beam-column

d. separate slab quarters

Student Name:_______________________

5. What is the typical drop panel size? ( 4 points)

a. thickness = slab thickness, length = slab span

b. thickness = 1/3 slab thickness, length = 1/2 slab span

c. x thickness = slab thickness, length = 1/3 slab span

d. thickness = 2 x slab thickness, length = 1/6 slab span

6. What is the minimum thickness for a concrete slab? ( 4 points)

a. x 4"

b. 6"

c. 10"

d. 12"

7. What is the required spacing for slab reinforcement to supply 0.20 sqin/ft

using No. 4s? ( 4 points)

a. 3"

b. 6"

c. 9"

d. x 12" see table B.2 in Appendix B Leet page 546 lecture notes

8. On a continuous slab additional reinforcement is required over the supports.

Where would you locate this reinforcement in the slab? ( 4 points)

a. x top

b. center

c. neutral axis

d. bottom

Short Answer Questions:

9. What are the three (3) selection criteria for concrete floor systems? (6 points)

colum spacing ( 2 points)

design loads ( 2 points)

head room ( 2 points)

10. Name six (6) concrete floor system types. (6 points)

Waffle Slab (1 point) Joist Slab (1 point)

Plate (1 point) Slab with beams (1 point)

One-Way Slab (1 point) Two-Way Slab (1 point)

Precast Tees (1 point) Precast Planks (1 point)

11. Name six (6) methods of structurally analyzing a two-way slab. (6 points)

Direct Design Method (1 point)

Equivalent Frame Method (1 point)

Finite Analysis (1 point)

Model Analysis (1 point)

Yield-Line Analysis (1 point)

Elastic Continuum (1 point)

Student Name:_______________________

12. Name the 6 conditions required by the Direct Method. (6 points)

1. At least three continuous spans must exist in each direction.

2. The spans must be similar in length.

Specifically, adjacent spans in each directions must not differ in length by more than

one third (1/3) of the longer span.

3. The live load must be uniform and less than 3 times the dead load.

4. The panels must be rectangular and

the long to short spans must not exceed 2.

5. If beams are present along column centerlines in each direction,

their relative stiffness must not be less than 0.2 or greater than 5.

6. Columns must not be offset more than 10 % of the distance between

center lines of successive columns in each direction.

13. Sketch the design moments distribution for the slab depicted below ( 6 points)

wu = 0.25 kips/ft

22' 24' 24'

14. The answer is "Two-way flat slab with drop panel and capital"

What was the question? (6 points)

What concrete floor system would be recommended

for a commercial building with a 15' to 40' span.

While minimizing the slab thickness and maximizing headroom.

Student Name:_______________________

Calculations:

Indicate what is given, asked, and what your solution is underline your answers.

Show all work, include formulas and units of measurement.

15. Problem: (13 points)

One way slab

The T-beam-and-one-way-slab system depicted below carries a live load of 60 lb/sqft and a uniform dead load of 120 lb/sqft. The dead load contains an allowance for the weight of the slab, beam stem, partitions, etc. The T beams are simply supported at each end and span 24 ft.

fc = 4 kips/sqin and fy = 60 kips/sqin.

Establish the minimum slab thickness d for the slab.

Student Name:_______________________

Calculations:

Indicate what is given, asked, and what your solution is underline your answers.

Show all work, include formulas and units of measurement.

16. Problem: (20 points)

Two-Way Slab

A flat plate floor with panels 20 by 24 ft is supported on 12 inches (45.7 cm) square columns. Interior exposure. No edge beams are used. From an investigation of a corner panel, what is the minimum required slab depth if deflection computations are not made?

fy = 40 kips/sqin (413.7 MPa), and

f'c = 3 kips/sqin (20.68 MPa)