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RE: Joints in concrete floor slab on bar joists

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My experience with this is that the system really works as a "two-way slab".
The bar joist and concrete deck on steel forms integrate well enough that
even under quite heavy loads you do not get a "one way slab" action. In
fact, I was even convinced that this works for a parking garage if the
joists are spaced closely enough (say 2'-3" to 2'-8" or so), and that even
if the joists are "K-series" joists that wouldn't normally be specified for
large concentrated loads such as in a parking garage.

Yet this still works, with "minimal" deck reinforcement (less than 0.18%,
the typical "temperature and shrinkage reinforcement" quantity), and NO
JOINTS whatsoever.

However, I have also seen problems where "extra-large" loading during
construction causes localized cracking that makes a real mess of things as
time goes on. This system has to remain "integrated" until ready for
service. I've had an engineer client get bitten badly in court because a
contractor rolled all over the **** place with a Lull.

-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
Sent: Thursday, July 08, 2004 6:00 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Joints in concrete floor slab on bar joists

Dave,

Concrete slabs on deck are rarely jointed.  The suggested reinforcement in 
the SDI manual is less than crack control steel per ACI.  And the 
reinforcing steel is placed solely for crack control.  I went through all of

the 20 years ago with Walt Schultz (R&D Vulcraft), and it has not changed.



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