TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
fr = 2.5of*m = 2.5o1350 psi = 91.8 psi
Where:
Ig = (7.62)(7.62)3/12 = 281 in4
Yt = 7.62/2 = 3.81 in
Since Mcr > Mmax;the lintel is not cracked, therefore Ig is used in lieu of I e.
(b) Since all the loadings are long term (dead load), the total lintel deflection, )mt, is determined
by modifying equation 8-4 as follows:
(c) Determine the allowable lintel deflection, )allow, and compare to the maximum lintel deflection,
)max = 0.30 in, as follows;
...Deflection O.K.
Shear Check
(a) Determine the shear loading, V, as follows:
Where:
W = The weight of the triangular shaped wall segment, lbs.
= (50psf)(4.0ft)(2.0ft)/2 = 200 lbs
(b) Determine the shear stress in the lintel due to loading, as follows:
Fv = Fv = 1.0of*m = (1.0)o1350 psi = 36.7 psi
(c) Determine the allowable shear stress, Fv, as follows:
Fv = 36.7 > fv. = 6.36 psi
...Shear O.K.
Bearing Check
(a) Determine the maximum bearing stress, f brg(max), assuming a triangular stress distribution as
follows:
Where:
Abrg = The bearing area of the lintel, in2
= 8 in 7.62 in = 61 in2
(b) Determine the allowable bearing stress, Fbrg, as follows:
Fbrg = 0.25(f'm)
= 0.25(1.350) psi = 338 psi
Fbrg =338 psi > fbrgmax =7.3 psi
...Bearing O.K.
8-5
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