Ultimately what you are doing with bridging is stabilizing the various compression elements in the assembly that make up a bar joist. By way of example: a deep long span bar joist can flip over just by its own weight.
The X bracing may provide an "anchor point" for the horizontal bridging. But an X brace WITH horizontal bridging is more positive and precludes the need for attaching the bridging to the wall. I recently started this practice in about 1977. I added up all of the costs for this since 1977 and it added up to zero dollars. That is twice my beer bonus for the year.
Regards, Harold Sprague
From: edjonson@msn.com
To: seaint@seaint.org
Subject: RE: Bridging for bar joist
Date: Wed, 28 Oct 2009 10:28:25 -0700
Thank you for your responce. I have older Vulcraft standard Details that shows bridging both ways, attached to wall and X braced. I prefer not to attach to wall because of no coordination between bridging location and panel joints and some panels are heavly reinforced which would require core drilling. Also if this was a steel building with spanderal beam i would think X bracing of bridging required.
So does X-bracing provide positive anchorage as required in SJI?
Date: Wed, 28 Oct 2009 12:16:01 -0400
Subject: Re: Bridging for bar joist
From: tm314052@gmail.com
To: seaint@seaint.org
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@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@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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