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RE: STEEL: Welding of Steel Bar Grating

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The National Association of Architectural Metal Manufacturers (NAAMM) has
metal bar grating manuals you can download. ANSI/NAAMM MBG 531-00 has
typical details for welded anchorage. The welds are not tack welds. They
show 3/16" x 3/4" welds close to the corners of each panel, with at least
one weld at intermediate supports.

I think properly welded grating does in fact provide considerable diaphragm
action to a floor system, but I'm inclined to treat it as "gravy" and show
what I want in the way of bridging on the drawings. I also think you should
indicate on the plans what you want in the way of welds rather than leaving
it to the installer's imagination. 

The grating supplier is unlikely to do this for you.

Jim Lutz, P.E., S.E.
Earth Tech, Inc.

10800 NE 8th Street - 7th Floor
Bellevue, WA 98004
(425) 698-1143 Direct
(425) 455-9494 Ext 7024
(425) 453-9470 FAX
http://www.earthtech.com




-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Thursday, February 03, 2005 4:32 AM
To: seaint(--nospam--at)seaint.org
Subject: STEEL: Welding of Steel Bar Grating


I want some other opinions--I've already formed my own.

I've got a contractor who in erecting an open-web steel joist-supported 
floor welded the steel bar grating to the tops of the joists (i.e. the 
top chord) with little fillets (essentially fat tack welds). He claimed 
that he "likes that better" than any other method including saddle clips.

Seeing as how the grating isn't directly a structural item, I forebore 
comment (though I think it's a sloppy method of attachment myself). But 
I pointed out that he had not provided additional bridging for lateral 
stability as I had expected to see, and as I had implied ought to be 
provided by notes on my drawings (that is, I indicated on the drawings 
that the steel joist fabricator should provide means for lateral 
stability as they deemed necessary since the bar grating would not be 
considered as providing lateral support).

The contractor replied "well, that's why I welded the grating! You can't 
tell me that's not sufficient support!"

Of course I can, and I did. I tried to be diplomatic about it, saying 
that I did not think the fabricator would agree with him. His response 
was that he'd "get a letter from the joist fabricator stating that it 
was all right."

Still haven't seen such a letter going on the second week. Has anyone 
run into anything like this before? Implicit in the presence of the 
welded grating is the notion that certainly some lateral stiffness has 
been provided, but I don't believe that I've ever seen any provisions or 
any research to suggest that this is sufficient.

Chime in if you would.

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