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Re: Rebar Strengths

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For your interest, we are currently looking at a structure built in the
early 40's with reinforcing specified as "structural grade". This implies
that the yield stress is 33 ksi.  Using this yield, some members are very
highly overstressed.  We have called for reinforcing tests and the one
result so far available shows a yield of 53 ksi.  Go figure!

Frank Hartzell

Original Message:

From: "Jason Kilgore" <jkilgore(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: Rebar Strengths

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I have a reinforced concrete building constructed in the "early 1920's".

The existing roof was obviously designed to carry future floor loads after
vertical expansion of the building (it's flat with a sloped wood overbuild
for drainage, vertical bars extend out of the top of the columns for future
lap splices, and the columns are relatively massive - 20" hexagonal columns
supporting less than 350 sq. ft. of roof).

Now, the owner wants to add some stuff to the roof.  What I need to to is
determine the capacity of the roof.

There was some testing done, and I have representative rebar information
(size, spacing, cover, etc.) throughout the building.  Also, cores were
taken (corrected f'c varied from 3640 to 4420 psi.  Unfortunately, no
testing was done on the rebar strength.  I know that some of the bars are
round and some are square.

Does anyone know what strength of rebar was used back then?  I have tons of
references concerning steel beams, but none concerning rebar.

Thanks for your help,

Jason Kilgore
Leigh & O'Kane, L.L.C.
816-444-9655 (FAX)

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