Page 275 - Design of Reinforced Masonry Structures

4.138 CHAPTER FOUR

4.20 A nominal 8 × 24 in. CMU beam is reinforced with one No. 8 Grade 60 reinforc-
ing bar for tension with d = 20 in (as shown in Fig P4.18). The beam is required to
carry a service dead load of 1.0 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. Design the shear reinforcement
m
for this beam.

7.63" (8" nominal)

d = 20"
24"

1#8
FIGURE P4.20

4.21 A nominal 8 × 24 in. simply supported CMU beam is reinforced with one No. 8
Grade 60 reinforcing bar for tension with d = 20 in. (as shown in Fig P4.18.) The
beam is required to carry a service dead load of 1.2 k/ft (including its self-weight)
and a service live load of 1.0 k/ft over a span of 12 ft. ′ f = 1500 psi. Design the
m
shear reinforcement for this beam.

7.63" (8" nominal)

d = 20"
24"

1#8
FIGURE P4.21

4.22 Figure P4.22 shows details of a concrete masonry wall having an 8 ft wide open-
ing. The wall is 8-in. thick (nominal) and grouted solid (medium weight units,
3
grout weight 140 lb/ft ). The reinforced masonry over the opening is to be utilized
as lintel. The wall supports two superimposed concentrated loads 8 kips each
(40 percent dead load and 60 percent live load), transferred to it as reactions from
roof trusses spaced at 8 ft o.c. The parapet extends 2 ft 8 in. above the roof level as
shown in the figure. Determine the tensile reinforcement (Grade 60) required for
2
the lintel if ′ =f 1500lb/in. .
m