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RE: Keyway Details

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Previously, I thought option 2 was the best, since it is the simplest.
However, we had one of our company's CM guys tell us that most
contractors like option 3 the best, because the "starter wall" cast with
the slab gives them something to tighten their wall forms against.
Also, one of our clients -- a water company that does a lot of junction
boxes -- has option 3 as one of their standard details, so we were
already using that detail on work for them.  So, I've converted to using
option 3 as my standard.  I like the fact that it eliminates the
conflict between the waterstop and the steel.  The contractors have a
hard enough time getting those waterstops in there where they should go,
as it is.

-- Joel

-------------------------
Joel Adair, PE
Halff Associates, Inc. 
E-mail: jadair(--nospam--at)halff.com 
-------------------------


-----Original Message-----
From: Michael L. Hemstad [mailto:hemstad.ml(--nospam--at)tkda.com] 
Sent: Wednesday, June 16, 2004 4:29 PM
To: seaint(--nospam--at)seaint.org
Subject: Keyway Details


We do a fair amount of wastewater and water treatment work involving
concrete tanks.  We go round and round about the joint between the slab
and the bottom of the wall.  These joints need to resist shear and
moment.  Basically we have three options we keep arguing about.

1. Finish slab flat, with keyway.  Put waterstop in bottom of keyway.  1
1/2 inch key plus half a 6 inch waterstop makes 4 1/2 inches.  Thus,
either make the slab 3 inches thicker than needed and hold the top mat
down, or bend the bars down under the wall (reducing their depth just
where it's most needed).

2. Finish slab flat.  Roughen under wall, dispensing with keyway.  Use a
4 inch waterstop, touching the top mat; tie it to the inside vertical
rebar.

3. Hang a 3 1/2 inch tall wall form, placing joint, key, and waterstop
up above the base slab.

I like option 2 myself; it's the simplest.  The wall will be rough there
anyhow because of the dowels sticking up in the way of the finisher.
Does anyone have any better ideas, or opinions on which of these options
is best?  Please weigh in with opinions and reasoning.

Thanks,

Mike Hemstad, P.E.
TKDA
St. Paul, Minnesota

P.S.  I've tried to send this several times.  By coincidence I notice
that the Digest was very short yesterday.  Has anyone else had trouble
sending to the List?

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