Page 273 - Design of Reinforced Masonry Structures

4.136 CHAPTER FOUR

4.12 For the beam described in Prob. 4.3, (a) determine the uniform load the beam can
carry over a span of 10 ft 8 in. if the dead-to-live load ratio is 0.7, (b) uniform
live load the beam can carry safely if the only dead load on the beam is its own
weight.
4.13 A two-wythe 8 × 24 in. clay brick beam has an effective depth of 20 in. It is
reinforced with one No. 7 Grade 60 bar for tension. Determine the cracking
moment of this beam (as shown in Prob. 4.10). ′ f = 2000 psi. Portland cement
m
Type S mortar would be used for construction. Does the beam satisfy the code
requirements?
8"

20"
24"

1#8
FIGURE P4.13

4.14 Check if the beam described in Prob. 4.8 would satisfy the code requirements for
cracking moment if it were reinforced with (a) one No. 4 Grade 60 bar instead of
one No. 5 bar, (b) one No. 7 bar instead of one No. 5 Grade 60 bar. ′ f = 2500 psi,
m
f = 60 ksi.
y
4.15 A nominal 8 × 24 in. concrete masonry beam is reinforced with one No. 9 Grade 60
reinforcing bar placed at d = 20 in. for tension (Fig. P4.15). The beam is required
to carry a uniform service dead load of 1.2 k/ft (including its self-weight) and a
service live load of 1.5 k/ft over a span of 12 ft. ′ f = 1500 psi. Check if the beam
m
is adequate to carry the load.
7.63" (8" nominal)

d = 20"
24"

1#9
FIGURE P4.15