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RE: Joist Girder Connections to Tubes

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Mike,

This is a fairly common approach for the wind world, and a bit more risky in
the high seismic world (not impossible, but more risky).  Vulcraft has done
this many times.  They even have a book on the topic.

The TS wall problem is solved by using a WT out of the AISC Manual or
fabricating a WT out of plates.  That way you make the wall whatever
thickness and length you need.  You should also check the side walls for
local buckling.  I have had occasion where I reinforced all 4 walls of a
column at the bottom chord connection point. 

There are many issues that require close coordination with the joist girder
supplier.  They will require a bigger bottom chord and the first couple
diagonals will increase.  They will also require bracing at the first bottom
chord panel point.

You may also want to require the erection bracing to remain until the
roofing has been placed.  It is best to get as much gravity load in place
prior to welding the bottom chord to the column.  That way the fixed end
moments due to gravity load are limited to LL and lateral load only.

Regards,
Harold Sprague


> -----Original Message-----
> From:	Michael Zaitz [SMTP:mzaitz(--nospam--at)hgbd.com]
> Sent:	Tuesday, June 27, 2000 3:21 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	Joist Girder Connections to Tubes
> 
> Hello
> 
> I have a project where, due to the schedule, it is desired to use TS10 x
> 10 x
> 5/16 columns.  The problem is that I have joist girders that I am using
> for
> frame action and therefore will have a concentrated load at my "stabilizer
> plate".  After performing the calc's for the tube from the black book
> (Hollow
> Structural Sections manual) the tube walls are not thick enough for my
> concentrated load using a vertical plate (to get it to work would require
> a 26"
> plate).  Has anyone else ran into this problem?  What other methods are
> there
> for connecting the bottom chord?  Last, is there any concern for the joist
> girder bottom chord for using an angle or plate horizontally instead of
> vertically (I am going to call Vulcraft on this)?
> 
> Mike
>