Page 230 - Design of Reinforced Masonry Structures

DESIGN OF REINFORCED MASONRY BEAMS 4.93

Load combinations:
1. U = 1.4D = 1.4(744) = 1042 lb/ft
2. U = 1.2D + 1.6L = 1.2(744) + 1.6(200) = 1213 lb/ft > 1042 lb/ft (governs)
r
1 213 20 67)
Design moment, M = wL 2 e = (. ) ( . 2 = 64 78. k-ft
u
u
8 8
1 213 20 67)
Design shear, V = wL e = (. ) ( . = 12 54 kips
u
.
u
2 2
b. 5 ft 4 in. wide window openings (Fig. E4.26C)
Top of wall
2'-8"
Roof line

9'-4"

45° 45° Top of opening

4'

5'-4"
Clear span, L
6'
Le, effective span
FIGURE E4.26C

Clear span (width of opening),
L = 5 ft 4 in. = 5.33 ft
Length of bearings on each side of the opening = 8 in. (assumed)

Effective span,
L = 5.33 + 8/12 = 6 ft
e
The minimum depth of masonry above the lintel required for arching action to
exist is

L e + 8 = 6 + 067 = 367. ft
.
2 12 2
Height of opening above the floor = 4 ft
Assume overall depth of lintel = 8 in. = 0.67 ft (least beam depth permitted)