sm7 93

________________________________________________________________________
PROBLEM (7.93) A 6-in.-wide by 10-in.-deep wood cantilever beam that is 5 ft long is
reinforced with 6-in.-wide and 1/8 -in.-deep steel plates on its top and bottom faces. The beam
supports to a uniform load of 150 Ib/ft over its entire length, as shown in Fig. P7.93. Determine the
maximum bending stresses in each material.
Given: Ew = 1.5 x 106 psi, Es = 30 x 106 psi
SOLUTION
y
y
20
sw
nEE== Equivalent wood section
Maximum moment occurs at the fixed edge:
22
max 1 1 0.15
( )(5 12) 22.5 .
2212
M
wL kip in== ×= ⋅
33 2
6(10) 120(0.125)
2[ 120(0.125)(5.0625) ]
12 12
t
I=+ + 4 1268.9 .in=
Hence,
3
max 22.5 10 (5)
( ) 88.66
1268.9
wt
Mc
p
si
I
σ
×
== =
3
max 20(22.5 10 )(5.125)
( ) 1.82
1268.9
st
nMc ksi
I
σ
×
== =
z
C
1/8 in.
1/8 in.
6 in.
z
Wood
C 10 in.
6x12=120 in.
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or
instructional purposes only to students enrolled in courses for which the textbook has been adopted. Any other
reproduction or translation of this work beyond that permitted by Sections 107 or 108 of the 1976 United States
Copyright Act without the permission of the copyright owner is unlawful.