Civil Engineering Reference
In-Depth Information
PROBLEMS
4.1
The estimated service or working axial loads and
bending moments for a particular column are as follows:
D
port a dead working floor load of 200 psf, which includes
the weight of the concrete slab and beams and a live
working load of 80 psf, determine the factored uniform
load for which the beams must be designed. (
Ans. w
u
4.416 k/ft)
16 ft-k.
Compute the axial load and moment values that must be
used in the design. (
Ans. P
u
100 k,
L
40 k,
M
D
30 ft-k and
M
L
184 k,
M
u
61.6 ft-k)
4.2
Determine the required design strength for a column
for which
D
4.4
Using the enclosed computer program, repeat the fol-
lowing problems:
(a)
Problem 4.1
(b)
Problem 4.2
(c)
Problem 4.3
120 k,
L
40 k, and wind
W
75 k com-
pression, or 90 k tension.
4.3
Reinforced concrete beams are to be placed 12 ft on
center under a reinforced concrete slab. If they are to sup-
In Problems 4.5 to 4.9 design rectangular sections for the beams, loads, and values given. Beam weights are not in-
cluded in the given loads. Show sketches of beam cross sections, including bar sizes, arrangement, and spacing. Assume
concrete weighs 150 lb/ft
3
.
Problem
D
not incl.
c
No.
f
y
(psi)
f
(psi)
Span
(ft)
beam wt(k/ft)
L
(k/ft)
c
0.18
f
4.5
60,000
4000
30
2
1
f
y
c
0.18
f
4.6
60,000
4000
28
1
2
f
y
1
2
4.7
50,000
3000
18
3
4
b
c
0.18
f
4.8
60,000
4000
32
2
1.8
f
y
1
2
4.9
60,000
3000
25
1.8
1.5
b
One ans.
Prob. 4.5: 16 in.
29 in. with four #10 bars.
One ans.
Prob. 4.7: 16 in.
28 in. with four #11 bars.
One ans.
Prob. 4.9: 14 in.
29 in. with four #9 bars.
