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RE: LGSS - Light Gauge Steel Stud question

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Unfortunately, removal of the header material is not possible since this
would require a tremendous amount of destructive work as well as be too
costly to repair. I believe that I have a couple of options that may be
unorthodox, but still may provide some bracking of the web.
A couple of questions and comments first:
1) the web of the WCJ sections are secured to the adjacent studs with 20
gauge plate material that overlape both the flang and stud face and is
secured in place with screws. This should prevent some web buckeling at the
supports where shear is highest.
2) I can add compression rods through the flanges (vertically) as needed to
push against the flanges in the same manner as suggested in the horizontal
direction.
3) The rod suggestion through the web can be secured on both sides with a
nut on the outside to prevent outward buckeling if necessary. Following this
method, the bolt can be a stove bolt so that the gypsum side can be hidden
in the finish and on the exterior side can be a bolted combination with a
spring/wing nut on the inside face. fastened tightly, the webs would be
braced both inward and outward. This would be especially effective for the
weaker gypsum side of the wall.
4) the foam idea would have been ideal since it would have taken most of the
gravity load off the webs and if any buckeling occurs, would probably be
very small and enough for the gypsum to control.

Question: How is buckeling calculated when the beam is a built-up box beam
with a top and bottom track to distribut load? I assume the H/t ratio of the
member for buckeling is determined by loading the individual section, not
the built-up member. Is this true?
Furthermore, a pony wall (cripple wall)is constructed above the header with
a continuous track supporting the trusses at each cripple stud. Is the
complete assembly considered in reducing the potential for web crippling by
creating a deeper composite type beam?

I think a lot of this has to do with engineering judgement than whether or
not the web will cripple in reality. Fortunatly, I was not the engineer who
designed these members or I would have followed the manufactures design
guides. The engineer who did the design also released a book recently on
Steel Stud Construction however, I have reviewed other work he designed and
found them to be less than adequate.

Since these are low income government subsidized housing, I need to
consider, in addition to the owners safety, the cost to repair and any
creative means to minimize this cost.

Thanks again for all of your help and suggestions. BTW, I went to the web
site you recommended - interesting, but many of the steel links are no
longer active. Still, I found the photographs enlightening.
sincerely,

Dennis Wish PE

"Science may have found a cure for most evils; but it has found no remedy
for the worst of them all- the apathy of human beings."
Helen Keller

|-----Original Message-----
|From: B D Pham [mailto:bpham(--nospam--at)airmail.net]
|Sent: Tuesday, March 17, 1998 8:37 AM
|To: seaoc(--nospam--at)seaoc.org
|Subject: Re: LGSS - Light Gauge Steel Stud question
|
|
|Dennis,
|
|The h/t ratio for both 20 gauge 8" and 12" sections exceed the AISI limit
of
|200 for unreinforced webs.  The allowable web crippling strength for a 20
|gauge 8" section is about 300 lbs. and for 12" section is about 250 lbs.
|
|For the 8" section, I would suggest removing the inside face of the header
|and reinforce both members with vertical stiffeners (something like an 8"
|piece of 3 5/8" track or stud material that would fit in between the flange
|of the header and screw it to the header) at bearings and concentrated
|loads.  With this kind of reinforcement, the load will transfer directly to
|the stiffener and then to the web and prevent the web from buckling.  And
|the member will meet the code h/t ratio limit of 260 for member with web
|stiffener.
|
|The h/t ratio of 12" section is still exceed the code h/t limit even with
|the web stiffener and  it would be better of to remove them and replace
with
|heavier gauge material.
|
|In theory for a CEE-Section,  the web most first likely buckle outward then
|fail and not likely buckle inward.  I am not sure that the bolt method will
|add any additional strength to web crippling strength.  The drywall will
|somewhat help to brace the web but to what degree is uncertain.  When the
|web starts to buckle, some of the load will transfer from the web to the
|drywall.  And you might want to consider if the drywall is stiff enough to
|prevent the screw from pulling through or cracking the drywall.
Personally,
|I would not feel comfortable using drywall as a stiffener for web
crippling.
|
|
|
|Bao D. Pham
|www.itecsteel.com
|
|
|
|
|