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Re: Lifts - concrete psi

To: Wayne Farrington <w.farrington@verizon.net>
Subject: Re: Lifts - concrete psi
From: Trevor Boicey <tboicey@brit.ca>
Date: Fri, 29 Aug 2003 12:56:08 -0400
Wayne Farrington wrote:
> What do you think? How critical is that 500psi? Is there a inexpensive way to
> test the psi rating of a slab? Would I be better off to cut two big square
> holes in the slab and pour two 6in. thick, 3000psi pads? 

   I guess it's easy for me to be Mr. Grumpy here, but I would be 
careful with that.

   As mentioned, it's almost impossible to load a two post lift balanced 
properly fore-to-aft, so you can be sure that there will be a tension 
load placed on the concrete at least some of the time.

   When I put my four post in, the thickness of the slab was 
disturbingly variable. I felt it was safe and met specs, but it was 
clearly not poured with the greatest of attention.

   With a four post like mine that is cable-strung, the only possible 
load on the beams is straight down, so the concrete requirements are 
pretty low. But a two-post is a different animal.


-- 
Trevor Boicey, P. Eng.
Ottawa, Canada, tboicey@brit.ca
ICQ #17432933 http://www.brit.ca/~tboicey/
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