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Re: Tack Welds

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Stan,
Thanks for elaborating a little more on your case. Hearing this story
gives me a better appreciation for the importance of joist bridging
attachments.

I can see where the weld of the joist bridging to the bottom chord might
improperly wind up being just a tack weld in many cases. For example, if
you look at the cover of the 40th edition of the SJI Manual, it shows a
welder sitting on top of a joist while welding bridging. It is easy to
see how he could get a decent 1/2" long fillet weld of the bridging
angle that runs underneath the top chord since the weld is basically
being made in the downhand position. 

On the other hand, assuming this same guy is still sitting on top of the
joist when he tries to weld the bridging angle that sits on top of the
bottom chord angles, he has two choices. One, he can do a sorry tack
weld in the downhand position where the bridging angle lies on top of
the vertical legs of the bottom chord angles, or two, if he is a
contortionist he can lean way over and do a 1/2" fillet weld underneath
the bridging angle. I wonder how this actually happens in the field?

Rick Burch
Hot and sticky also in Columbia, SC






> "Caldwell, Stan" wrote:
> 
> Rick (and Casey, too):
> 
> Consider a situation where several bays of roof collapse in two
> adjacent five-year-old warehouses during a thunderstorm that arguably
> produced "fastest mile" winds of only 65 mph (UBC-91 code winds are 70
> mph).  The roofs have very little dead load, with only a
> polyisocyanurate insulation board and single-ply EPDM membrane over a
> 22 gage wide-rib steel roof deck.  It is alleged that the open-web
> steel roof joists failed in buckling caused by wind uplift.  Now,
> consider what the uplift resistance might be if the lower chords of
> the roof joists were not laterally braced by the lines of bridging
> (nil, nada, zero).  That is why the tack welds have become very
> important!
> 
> Stan R. Caldwell, P.E.
> Sweating in Sunny, Sticky Dallas
> 
> ¤º°`°º¤ø,¸¸,ø¤º°`°º¤ø¤º°`°º¤ø,¸¸,ø¤º°`°º¤ø¤º°`°º¤ø,¸¸,ø¤º°`°º¤
> 
> -----Original Message-----
> From: Rick Burch [mailto:rburch(--nospam--at)conterra.com]
> Sent: Sunday, June 22, 2003 7:40 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Tack Welds
> 
> Stan,
> Am I understanding correctly, that this case is about the welds of
> joist bridging to the joist chords?  I never thought about this being
> a serious source of liability before, so I would be interested in
> hearing more. On a lot of jobs I visit during construction, the joist
> bridging is not even anchored at the ends until I write it up in my
> site visit report, but I never thought of paying much attention to the
> welds of the bridging angles to the joist chords until you mentioned
> this case.
> 
> I know that in lawsuits, one issue can cause the original problem and
> then the lawyers hire engineers to scrutinize everything and
> collateral issues get brought in. Was this the case here? It's hard to
> imagine a $4.3 million lawsuit solely about joist bridging.
> 
> Rick Burch
> Columba, SC

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