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RE: Light Gauge Steel - Full-Compliance Design

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I spend my first two years out of college at a LSF manufacturer and have the
following comments on Lynn's


	1. Odds are your connnections will govern.  I suggest using the no lighter
than 16Ga, 33ksi while keeping the straps as thin as possible.  If extra
capacity is required, go wider, up to 6".  The thicker the straps are, the
greater the bulge in the sheetrock.
	2.  Use straps in both direction on both sides of wall (I would mandate
this for walls 6" deep or grater) due to eccentricity.
	3.  On installation, have the contractor tension the straps prior to
permenantly attaching them (probably a no brainer, but I've heard of them
being installed with slack).
	4.  Do no attach the strap to the intermeadiate studs.  Any force in the
straps will go to the studs and cause weak axis bending.
	5.  Try not to change the size and gauge of the posts if possible.  18 GA
looks and feels a helluva lot like 16 GA. Also, ever tried driving a #10
screw into 12 GA?  It make you cry, then try it with a #8 drywall screw and
see what happens.
    	6.  Check out www.lgsea.com for and tech reports you may need.  I read
one once on diafram action that was real good.
	7.  Either spec out inline framing or use a structural tube at the top of
the walls to prevent weak axis bending.

I hope this helps,

David Tehranchi

-----Original Message-----
From: Lynn H [mailto:lhoward(--nospam--at)silcom.com]
Sent: Sunday, October 01, 2000 7:21 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Light Gauge Steel - Full-Compliance Design


Dennis-

We have done projects like this for the military.
No wood at all present in the structures.

Metal stud walls, light gauge steel joists for the
floor supporting a metal deck and concrete, and
steel light gauge trusses for the roof.

The floor metal deck was one of those inexpensive
"waffle" type that was only 3/4" deep.  The deck
only had to span between the joists, so it was
adequate.  The concrete floor was considered rigid
and seismic forces were distributed to the shear
resisting elements based on the stiffness of each
element.

For shear walls we used nonproprietary tension only
braced frames, utilizing flat 10 ga. sheet metal
straps.  Holdowns were steel angles bolted to the
concrete slab, and the diagonal straps were welded
to the angle.  A heavy gauge double metal stud was
used at the holdowns.

These were used in areas of the world where wood is
not available (actually most of the world).  They
were very affordable and easy to put together.  They
were somewhat more expensive than conventional wood
framed, but not a significant premium.  The
contractor specializes in building housing for the
military in this country and all over the world
wherever there are US bases.  They do A LOT of both
wood framed, and metal buildings.  They seem to
prefer the wood framed, as it is somewhat less
expensive.

Hope this helps.

Lynn



"Dennis S. Wish" wrote:
>
> I am bidding a project in which the Architect wants to use Light Gauge
Steel
> for everything - including roof trusses or joists (for flat roof areas). I
> am restricted to the UBC values for plywood shearwalls and will probably
> substitute braced frames or Hardy Frames/Panels where higher shears
require
> stiffer elements.
>
> Has anyone completed a full compliance design on a light-gauge steel
> structure? If you have, how did you address the horizontal diaphragm
issues
> (deflection, flexibility) as well as the shear distribution by torsion?
Did
> you assume the empirical wall deflection calculations or is there an
errata
> to the code that goes into greater detail on vertical and horizontal panel
> deflections for cold-form steel?
>
> Regards,
> Dennis S. Wish, PE
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