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Re: Bridging for bar joist

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It depends on structural engineer's level of comfort with the Joist - Bridging
and reinforced concrete system.

For high loads especially those involving LH series joists and girders, I
normally ask for some kind of connection at the bottom level making sure that welds are just there for stability and not the load transfer. Do not weld to transfer any kind of loads or moment transfer if any ~ its just to stabilize the joist or girder. Load will be transferred by your main conxxn on top. Normally a 1'-0" x 1'-0" embed in precast panel or wall with flat plate welded to the 1 ft^2 embed and inserted between bottom legs of joist or girder will be enough.

Naeem Ghani, P.E.



On Oct 28 2009, Thomas Magnum wrote:

My guess is that there is a misunderstanding.  You do not use braces to
provide positive anchorage. They stabilize, not anchor.  It's now standard
(page 33 of the '03 Vulcraft Catalog) to provide horiz bridging in the bay
adjacent to a much stiffer element such as a wall.  What sort of concrete
panel is it?  Could it be that the joist manuf thinks the bridging will be
used to stabilize them?  Are the panels more of a cladding than a support?

Byron

On Wed, Oct 28, 2009 at 11:50 AM, Kipp Martin <KMartin(--nospam--at)carollo.com> wrote:

 Ed,

I don't do a whole lot of work with steel joists, so keep that in mind.
I've usually seen that X-bracing converted to horizontal bracing in the end bay. This is to allow the joist to deflect releative to the non-deflecting
wall.  I usually allow the use of either X-bracing or horizontal bracing,
leaving it up to the joist manufacturer. But in answer to your question, I
don't see how X-bracing does not provide positive anchorage.  I'd ask the
joist manufacturer to explain.

--Kipp Martin
  Carollo Engineers
  Portland, Oregon
 ------------------------------
*From:* Edward Jonson [edjonson(--nospam--at)msn.com]
*Sent:* Wednesday, October 28, 2009 7:43 AM
*To:* seaint
*Subject:* Bridging for bar joist

 Question about anchorage of bridging.  I have project where X-bracing of
end bay of bridging is called out on plans rather than continuing bridging
to concrete panels.  Joist manufacture claims this X-bracing does not
provide positive anchorage. So the question is does the X-bracing provide
positive anchorage?  Any comments much appreciated.

Ed Jonson



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