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Re: Top Rebar??

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The ACI 318-83 commentary has some discussion on the multiple layers
(12.2) - I don't know how help it will be to you.

I distinctly remember a phrase "multiple layers of reinforcing in walls need
not be considered top bars", but I am not sure if I saw that in a code or in
the general notes of some plans.

David Finley, P.E.

-----Original Message-----
From: Tom.Hunt(--nospam--at) <Tom.Hunt(--nospam--at)>
To: seaint(--nospam--at) <seaint(--nospam--at)>
Date: Saturday, March 17, 2001 7:27 PM
Subject: Top Rebar??

>Speaking of seawater structures, I have received an interesting plan check
>comment.  We have designed a rather large double cell box culvert with good
>size rebar vertically and horizontally in the walls due to a significant
>surcharge from a nearby railroad.  The plan checker has requested that we
>consider all HORIZONTAL wall bars as top bars in designing our splices.
>Now I know that the code reads that top bars are those with 12 inches or
>more of fresh concrete below but I have only used this in slabs and beams.
>I reviewed several texts and did not find anything definitive.
>When I was in school I was told that the top bar reduction was due to the
>possible accumulation of micro air bubbles rising to the surface.  Would
>this apply to all the horizontal bars in a 2 foot thick by 16 feet tall
>wall??  I have been given widely different opinions on both sides of the
>Thomas Hunt, S.E.
>Duke/Fluor Daniel