sm7 97

________________________________________________________________________
PROBLEM (7.97) For the composite beam with the cross section shown in Fig. P7.97,
calculate the permissible bending moment M about the horizontal (z) axis.
Given: (b
σ
)all = 17 ksi, (
s
σ
)all = 20 ksi, Eb = 15 x 106 psi, Es = 30 x 106 psi
SOLUTION
Use Brass as reference material. Thus
30 2
15
s
b
E
nE ===
For transformed section:
23
11
(1.5)(1) (1.0)(1)
12 12
t
I=+
y
z
1.5 in.
Brass
1.0 in.
1 in.
Trandformed brass section
34
208(10 ) .in
−
=
Brass : 0.5 . ( ) 17
ball
y
in ksi
σ
==
33
(0.5)
;17(10)
208(10 )
all t
My M
I
σ
−
==
or
7.07 .
M
kip in=⋅
Steel : 0.5 . ( ) 20
sall
y
in ksi
σ
==
33
(2) (0.5)
; 20(10 ) 208(10 )
all nMy M
I
σ
−
==
or
4.16 .
M
kip in=⋅
Hence
4.16 .
all
M
kip 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.