Page 269 - Design of Reinforced Masonry Structures

4.132 CHAPTER FOUR

4.2 A 10 × 40 in. (nominal) concrete masonry beam is reinforced with two No. 7
Grade 60 reinforcing bars positioned at 34 in. from the compression face (Fig. P4.2).
Calculate (a) moment of inertia of gross section, (b) moment of inertia of cracked
section (c) cracking moment, (d) fM of the beam, and (e) check if the beam
n
satisfies the code requirements. Assume ′ f = 2000 psi.
m
9.63" (10" nominal)

d = 34"
40"

2#7
FIGURE P4.2

4.3 An 8 × 24 in. (nominal) concrete masonry beam is reinforced with one No. 5
Grade 60 reinforcing bar positioned at 20 in. from the compression face (Fig. P4.3).
Calculate (a) moment of inertia of cracked section (b) cracking moment, (c) fM
n
of the beam, and (d) check if the beam satisfies the code requirements. Assume
′ f = 1800 psi.
m

7.63" (8" nominal)

d = 20"
24"

1#5
FIGURE P4.3