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RE: CFS Roof Trusses

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About a month ago I attended a seminar in Birmingham put on by Unimast.  The focus of the seminar was on light gauge trusses.  Unimast uses a proprietary shape for its truss chords that is basically a U shape (I don't recall them having punchouts).  The webs are square in shape and fit in the trough formed by the U.  This gets rid of the eccentricities that back to back studs have.

Technical handouts were provided that went into a fair amount of detail.  They will probably send you any handouts you need.  The head research engineer was the person giving the speech.  I believe he was headquartered in Atlanta.  I don't have the number with me, however, I'll try to get it and post tomorrow.

-----Original Message-----
From:	CanitzCF [SMTP:CanitzCF(--nospam--at)aol.com]
Sent:	Thursday, January 08, 1998 10:51 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	CFS Roof Trusses

I recently received information from Unimast Inc. which included CAD CFS roof
truss details. All the deatils included a note stating that all truss
members(chords, verticals and diagonals) shall not include web punchouts. I'm
curious why this is a requirement since the trusses are fabricated using stud
members(CSJ members using Unimast's designation). Said members when used for
exterior wall assemblies are typically furnished with punchouts and are
usually subjected to combined axial and flexural stresses. Is the concern that
punchouts may occur at a panel point? Could not the design documents require
that truss member punchouts not occur within a prescibed distance near the
panel point?

I reviewed the AISI's '"Design Guide For Cold-Formed Steel Trusses" and HUD's
"Prescriptive Method For Residential Cold-Formed Steel Framing(1st edition)".
Neither of said documents preclude the use of web punchouts for truss members.


Charlie Canitz, PE
Bel Air, MD



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