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RE: handling joist deflections / alignment when in parallel with bearing wall

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By cutting the span of the deck adjacent to the wall, you are helping
that section of deck adjacent to the wall.  The next span in that is
6'-0" will see the same out of plane load, so cutting down the adjacent
span seems like a moot point.  I prefer a full span adjacent to the wall
to allow the joist to deflect.


Charles F. Espenlaub, III, P.E.
Martin-Espenlaub Engineering



-----Original Message-----
From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)bv.com]
Sent: Tuesday, June 06, 2000 2:56 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: handling joist deflections / alignment when in parallel
with bearing wall


Bob,

The reason that I reduce the spacing for the last joist is to cut down
on
the unbraced length of the deck to resist out of plane forces on the
wall.
If the first joist is 5'-0" or 6'-0" from the wall the compressive
strength
of the deck takes a nose dive.  

If you put the last joist too close to the wall, you have the problems
that
you stated.

Regards,
Harold Sprague


> -----Original Message-----
> From:	Bob Shaw [SMTP:rshaw(--nospam--at)steelstructures.com]
> Sent:	Tuesday, June 06, 2000 3:32 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	RE: handling joist deflections / alignment when in
parallel
> with bearing wall
> 
> I think Harold has the right solution (as he always does). Place the
joist
> away from the wall (I'd use a standard joist spacing, not the 2'-6"),
and
> attach the deck to an embed plate or angle.
> 
> It is important to keep the joist away from the wall when running
> parallel.
> When loading is applied to the roof, the joist will deflect, but the
wall
> is
> fixed, and you put plenty of flexure into the roofing material over a
very
> short distance. Good place for a roof leak to develop over time,
> particularly when roofing materials get brittle.
> 
> Bob Shaw
> Steel Structures Tech Center
> www.steelstructures.com
> 
> -----Original Message-----
> From: Khosrownia, Ghassem SPK [mailto:GKhosrownia(--nospam--at)spk.usace.army.mil]
> Sent: Tuesday, June 06, 2000 7:42 AM
> To: 'seaint(--nospam--at)seaint.org'; Darrel E. Marchall (E-mail)
> Subject: handling joist deflections / alignment when in parallel with
> bearing wall
> 
> 
> A nagging problem that needs good solid solution!
> 
> Situation:
> Roof joists run in parallel with CMU bearing wall.
> Roof is gabled, joists will be double gabled (no ridge beam).
> CMU wall follows slope of roof.
> 
> Problem:
> Camber and deflection of joists make it nearly impossible to line up
with
> the top of the wall?
> Construction tolerances for the wall and bearing of the joist could
> compound
> this effect.
> 
> Solution:
> Specify top of the wall to be slightly lower than the bottom of the
> decking.
> Use light enough decking so it is a bit more flexible.
> For interior walls running in parallel with the joists discontinue the
> decking to obtain more flexibility. Weld both ends of the decking to
the
> steel bearing plate on top of the wall. Use washers or small plates to
> compensate for the inaccuracy.
> 
> These are not meant to be independent solutions, rather a total
recipe.
> 
> What do you think. What have you done to remedy this situation?
> 
> Ghassem.
> 
> 
> 
> 
>