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RE: LGSS - Light Gauge Steel Stud question

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I appologize to those trying to read my original question. I tried to keep
my fingers in pace with my thinking and did not check my post before
sending. Please re-read the message below - I have cleaned it up somewhat.

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: Dennis S. Wish [mailto:wish(--nospam--at)cwia.com]
|Sent: Tuesday, March 17, 1998 12:12 PM
|To: seaoc(--nospam--at)seaoc.org
|Subject: RE: LGSS - Light Gauge Steel Stud question
|
|
|--------------------------------------------------------------------------
|Your following message has been delivered to the list
|  seaoc(--nospam--at)seaoc.org at 12:17:33 on 17 Mar 1998.
|--------------------------------------------------------------------------
|
|
|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 bracing of the web.
|A couple of questions and comments first:
|1) the web of the WCJ sections are secured to the adjacent studs with a 20
|gauge plate that overlaps both the stud and beam web. The plate 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
|brace the webs. This is similar to the horizontal bolt suggestion through
the center of the web.
|3) The rod suggestion through the web can be secured on both sides with a
|to prevent crippling both inward and outward. A stove bolt can be installed
with the head on the inside face of wall. The head of the bolt would be
concealed in the gypsum wall board since it is less than 1/4" deep. A washer
and nut can be threaded over the stove bolt to hold it flush to the web on
the inside face of wall. The exterior can be secured with the spring/wing
nut as I suggested before. I can be installed and set tight to the outside
web (within the box beam) and the exterior face of the outside web can be
secured with an oversize washer and nut to hide the enlarged hole.
|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. I found out that it would
be too difficult to remove the inside face of beam or enough of it to pull
the insulation out and allow the cavity to be sealed with expandible foam.
|
|Question: How is buckeling calculated when the beam is a built-up box beam
|with a top and bottom track to distribute load? I assume the H/t ratio of
the
|member for buckeling is determined by loading the individual section, not
by considering 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 creative engineering. 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
||
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