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RE: LGSS - Light Gauge Steel Stud question

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Ernie,
I have the same problem with web crippling. For one major reason, there is
not industry standard on section properties as yet. Yes, there are those
trying to create the standard, but without the manufactures stats it almost
impossible to be accurate. In my case, the manufacture refuses to submit the
information I need and I am now recommending that the company I'm working
with change sources.
My biggest concern is that they constructed over 300 homes in this manner
before I ever entered the picture. I don't know if they used a prescriptive
measure or were required to have engineering. I do know that the steel is
the wrong gauge, the manufacture who produced it special never questioned or
raised a concern that the H/t ratio for web crippling is grossly exceeded
and may require analysis by their engineer. Instead they have been ordering
materials the same way for years.
Furthermore, I was only required by the local authorities to provide lateral
designs (my only liability) until this phase where the city inspector asked
to have the headers looked at by an engineer. I found out at this time that
they were 20 gauge material and assumed them to be thicker based upon the
avialability of materials in the manufactures catalog. The markings on the
steel were on the inside which were buried in the box beam and could not
easily be verified. Fortunately the homes that had not yet been constructed
had material sitting out in the open that we checked.
I just came back from the site and installed one of the bolted connections.
On the garage header, the loads are small only about 5 feet of tributary at
the worst case. On one of the homes that already had tile roof's in place,
you could hear the web as you were able to flex it inward. The amount of
crippling was small but was there none the less.
I failed to note that the outside face of the garage header was sheathed in
plywood. This should restrain the buckeling outward. Since the plywood is
stitched to the header, the bolted connection will draw the inside flange
tight to the plywood braced outside.
Finally, as you pointed out, the analysis for web crippling is very
intensive and this is one time that I believe we need to use engineering
judgement in the field. I ran down to the hardware store, bought $1.15 worth
of toggles, bolt and washers and nuts. Ran back to the job site. I bought a
hunk of PVC 1/2" ID pipe and notched out one end to fit around the spring
wing nuts. This way I could slide the pipe over the bolt and hold the wing
nut in place while it was tightened from the outside. The second spring wing
nut is reversed to come flush to the inside face of the outter web. Once it
expands through the hole, I insert the pvc pipe notched end to grab it and
wind it back out until it comes flush with the web. Then simply remove the
pipe, slip an oversized washer in place and secure with a nut.
Once I showed them how to do it, they saw that it cost about $1.20 a
connection plus 5 minutes of labor to install. They gave up the welded idea.
sorry to take so long with this, but I can not think of anything else to
help them. The ideal solution would put them out of business - seriously.

Thanks for your help as well as everyone else that offered ideas.

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: ErnieNSE [mailto:ErnieNSE(--nospam--at)aol.com]
|Sent: Thursday, March 19, 1998 9:52 AM
|To: seaoc(--nospam--at)seaoc.org
|Subject: Re: LGSS - Light Gauge Steel Stud question
|
|
|Dennis,
|
|They could countersink the screw at the stucco side and patch it.
|
|I'm just worried in your solution not really providing in 'essence' the
|required stiffeniing requirements when the h/t is exceeded. It's OK if you
|really feel that stiffening is essentially provided. Just be careful with
your
|analysis.
|
|I've been reading the basis of how web crippling occurs and it is too
|complicated for me to comprehend with a limited time I have. Therefore, I'm
|not in a position to use judgement and assume a certain equivalent
restraining
|method will be really equal to the prescribed stiffening requirement. I'd
be
|more conservative if it were my job although I know the constraints in your
|case.
|
|Ernie Natividad
|
|
|