Cross

section stability of structural steel
Exercises targeted at undergraduate level
Software
www.ce.jhu.edu/bschafer/cufsm
Tutorials
www.ce.jhu.ed
u/bschafer/aisc
[Checkup on Tutorial #1]
1)
Using finite strip analysis and the program CUFSM, what is the elastic local
buckling stress of a W36x150 section in pure compression?
2)
Again for this W36x150, at what moment does elastic local buckling occur if
be
nding is about the strong axis?
[
Applying
Tutorial #1]
1)
For
a
W36x150 what is the elastic weak

axis flexural buckling stress for a pin

ended member which is 30 ft. long?
2)
Again for the same W36x150, at what moment does elastic local buckling occur if
bendin
g is about the weak axis?
[Checkup on Tutorial #3]
1)
How does the elastic local buckling stress change if the web thickness is increased
in a W36x150 to be the same as the flange thickness
for the section in pure
compression
?
2)
How does the elastic local buck
ling stress change if the flange thickness is
decreased by 2 in. in a W36x150
subject to pure compression
?
[Applying Tutorial #3]
1)
Load the W14x120 cross

section and make the same changes as Tutorial 3 on this
cross

section and observe the impact, i.e.,
a.
de
termine the elastic local buckling stress and global buckling stress at 40
ft. for the W14x120 in pure compression
b.
make the web thickness the same as the flange thickness and examine the
impact on the
local buckling stress for the section in pure compressi
on
,
report the change in the local buckling stressm global buckling stress, and
observed behavior.
c.
make the flange 2 in. narrower and examine the impact on the local
buckling stress for the section in pure compression
, report the change in
local buckling s
tress, global buckling stress, and observed behavior.
d.
how is the W14x120 different in its response than the W36x150
?
[Exploration of other cross

sections]
1)
For each of the following cross

sections find the elastic local buckling stress in (i)
pure compress
ion and (ii) for restrained bending about the global x

x axis using
CUFSM
(a) W14x120
(b) C5x9
(c) L4x4x1/2
(d) WT 18x150
(e) HSS 4x4x1/2
2)
Compare your W36x150 results with your WT18x150, what is the impact of
slicing the W36x150 in half on local buckling?
on global buckling?
3)
Compare your L4x4x1/2 with the HSS4x4x1/2, what is the impact of having all
four side connected as in the HSS section as opposed to the L

section on local
buckling? on global buckling?
[Small project / Group project]
1)
Consider pure com
pression load on the W36x150, keeping the total area constant
modify the cross

section such that the local buckling stress is increased by at least
50%. (You are asked to use creativity and trial and error to find this solution, note
you can see your curre
nt “area” in the properties page it should be nearly the same
as the original W36x150 area
–
you may change thickness, dimension, whatever
you choose in this part)
2)
Can you modify the cross

section in such a way that the local buckling stress
increases AND
the global buckling stress at 20 ft.
also increases AND the section
remains its centerline depth of 35 in. all while keeping the area constant?
(To
achieve this you may have to be quite creative in how you use the material
and the
improvements may be modes
t, see how much better you can make this section..)
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