Civil Engineering Reference
In-Depth Information
4.29
Determine the depth required for a beam to support itself only for a 500-ft span. Neglect cover in weight calcula-
tions. Given
4000 psi,
f
y
60,000 psi, and
0.5
b
. (
Ans.
67.77 ft)
4.30
Determine the stem thickness for maximum moment for the retaining wall shown in the accompanying illustra-
tion. Also, determine the steel area required at the bottom and mid-depth of the stem if
4000 psi, and
f
y
60,000
psi. Assume that #8 bars are to be used and that the stem thickness is constant for the 20-ft height. Also, assume that the
clear cover required is 2 in.
0.18
f
c
f
c
f
c
/
f
y
.
4.31 (a)
Design a 24-in.-wide precast concrete slab to
support a 60 psf live load for a simple span of 15 ft. As-
sume minimum concrete cover required is in. as per
section 7.7.2 of the Code. Use welded wire fabric for re-
inforcing,
f
y
60,000 psi and
4.32
Prepare a flow chart for the design of tensilely rein-
forced rectangular beams.
5
8
4.33
Using the enclosed CD-ROM, solve the following
problems.
(a)
Problem 4.6. (
Ans.
18 in.
28 in. 4 #10 bars)
(b)
Problem 4.18. (
Ans.
18 in.
39 in. with 8 #10 bars)
c
4000 psi.
f
c
/
f
y
.
3
2
(
Ans.
in. slab)
(b)
Can a 300-lb football tackle walk across the center of
the span when the other live load is not present? Assume
100% impact. (
Ans.
yes)
0.18
f
Problems in SI Units
In Problems 4.34 to 4.39 design rectangular sections
for the beams, loads, and
values shown in the accom-
panying illustrations. Beam weights are not included
in the loads given. Show sketches of cross sections
including bar sizes, arrangements, and spacing. As-
sume concrete weights 23.5 kN/m
3
,
f
y
420 MPa, and
28 MPa.
Problem 4.35
(
One ans.:
450 mm
890 mm with 6
#32 bars.)
L
= 100 kN
D
= 25 kN/m
c
f
1
2
=
6 m
6 m
Problem 4.34
b
12 m
