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CEE 111 Design Exercise 2
Winter 2012
January 30, 2012
Work independently!!!
Consider the structural wideflange (WF) beam shown in the figure below:
65,000 LB
135,000 LB
5 ft
5 ft
10 ft
AB
C
D
The wideflange beam is to be designed to carry a total load of 200,000 lbs, distributed as
shown above, at minimum cost.
The maximum allowable bending stress,
ballowable
(in
either compression or tension), in the beam is 50,000 psi.
The maximum allowable shear
stress,
sallowable
, in the beam is 45,000 psi.
The formula for bending stress in a beam is
b
XX
My
I
(1)
where
b
is the bending stress,
M
is the external bending moment,
y
is the distance
from the neutral axis, and
XX
I
is the moment of inertia about the neutral axis. The
formula for shear stress in a beam is
s
s
F
A
(2)
where
s
F
is the shear force in the beam, and
A
is the crosssectional area of the beam.
For the wideflange (WF) beam shown below, the maximum bending stress is given by
max
2
b
XX
Md
I
(3)
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View Full DocumentThe specifications of the wideflange (WF) beams that are available from the steel
supplier are shown in Table 1 (and in the spreadsheet “WF_Beams.xlsx.”)
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 Winter '12
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