TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
Where:
Ra = The reaction at the bottom of the wall, pounds.
(e) Determine the axial load stress on the edge stiffener, fa. Assume the lintel over the door is fully
grouted from the top of the opening to the top of the wall.
Where:
w3 = The weight of the stiffener, lbs/ft.
Ls = The width of the stiffener, feet.
t = The thickness of the stiffener, inches.
RL = The lintel reaction, lbs.
= (P)(Lp) + (w2)(d)(LL/2)
Where:
w2 = The weight of masonry above the opening, psf.
d = The height of the lintel, feet.
LL = The length of the lintel, feet.
RL = (300 lb/ft x 7.33 ft) + (92 lbs/ft2)(2 ft)(12 ft/2)
= 3303 lbs
= 26.3 lbs/in2
(f) Determine the allowable axial stress, Fa.
(g) Rearrange the interaction equation and determine the required resisting moment, Required Mr.
= 7236 ft-lbs
From table B-7 two 8 inch wide 12 inch deep stiffeners with 2-#6 bars furnish a resisting moment, Furnished
Mr, as follows:
Furnished Mr = 2(3997 ft-lbs) = 7994 ft-lbs
Furnished Mr = 7994 ft-lbs > Required Mr = 7236 ft-lbs
...O.K.
(h) Check the combined axial and bending stresses as follows:
...O.K.
(4) Summary. A 12 inch by 16 inch wall stiffener with 4-#6 bars, as shown in figure 6-4, will resist the
given loads.
6-9
Previous Page
