I asked S.K. Ghosh this exact question, and his answer was that the top bar
factor was not meant to apply to horizontal bars in walls. Furthermore, many
senior engineers that I know do not use it either.
----- Original Message -----
From: "Calvin Chang" <ccpe(--nospam--at)ms38.hinet.net>
Sent: Sunday, March 18, 2001 8:07 PM
Subject: Re: Top Rebar??
> Would this apply to all the horizontal bars in a 2 foot thick by 16 feet
> Yes, I think so.
> Top bars must be HORIZONTAL BARS with 12 inches or more of fresh concrete
> All the main reinforcements of columns are not TOP BARS because they are
> VERTICAL BARS, even if the columns are very tall.
> Calvin Chang
> ----- Original Message -----
> From: <Tom.Hunt(--nospam--at)d-fd.com>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Sunday, March 18, 2001 8:49 AM
> 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
> 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