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RE: Minimum Reinforcing for thick slab on ground

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It is a structural slab, in that it is a mat footing for machine equipment.  The top of the mat footing also serves as the slab walking area.  I do have bottom reinforcing running in both of the primary directions.  Top is not required by analysis.  I was wondering if I would get lots of cracks on the top surface from shrinkage and should reinforce for it.

 

 

Rich Lewis

Lewis Engineering

 

-----Original Message-----
From: THunt(--nospam--at)absconsulting.com [mailto:THunt(--nospam--at)absconsulting.com]
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Thursday, December 23, 2004 9:51 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Minimum Reinforcing for thick slab on ground

 


Rich,

The first thing to ask is "is this a STRUCTURAL slab?".  If this is a simple slab on grade without significant shears or moments then it is not governed by ACI 318.  If this IS a structural slab, then the temperature steel is only required normal to the flexural reinforcement.  Note also that there is no reason to put it all in the top and for a slab this thick you would probably want to split it top and bottom.

That said, realize a slab this thick will generate a lot of internal heat and a mesh of rebar top and bottom is a very good idea regardless of what the code says.

Thomas Hunt, S.E.
ABS Consulting


"Rich Lewis" <sea(--nospam--at)lewisengineering.com>

12/23/2004 07:20 AM

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Minimum Reinforcing for thick slab on ground

 

 

 




I am designing a concrete mat, 3 ft. thick, which will serve as the top of slab as well.  My questions is do I need to provide the minimum top steel of 0.0018% of gross area for shrinkage control based on the overall depth?  Is there a reduction for this for extremely thick slabs?

 

 

 
Rich Lewis
Lewis Engineering