Another resource is FEMA 273, NEHRP Guidelines for the Seismic
Rehabilitation of Buildings. Look at Tables 6-1 and 6-2. Table 6-1 lists
available grades by years. Table 6-2 lists by ASTM designations. Also, they
used to call rebar grades out by a title rather than yield stress. The
grades available were Structural (33ksi yield), Intermediate (40 ksi) and
Hard (50 ksi). The FEMA tables show that the 33 ksi yield bars were
available until 1966.
From: Pat Bachman [mailto:BachmanPM(--nospam--at)c-b.com]
Sent: Friday, March 16, 2001 11:53 AM
Subject: Rebar Grades
The AASHTO Manual For Condition Evaluation of Bridges, 1994 recommends the
following in Section 220.127.116.11:
Unknown grade prior to 1954, Fy = 33 ksi
Unknown grade after 1954, Fy = 40 ksi
If you can find anything on the plans indicating Fs used for design, you can
be pretty sure that if:
Fs = 18 ksi, Fy = 33 ksi
Fs = 20 ksi, Fy = 40 ksi
Fs = 24 ksi, Fy = 60 ksi
As for area of square bars, I have found nothing to use except a calculated
value based on provided dimension.
Good Luck, Patrick Bachman, P.E.
*** Original Message ***
I am working on rehabilitating a 1950 concrete seawater intake structure
that was designed per the 1946 Uniform Building Code. The drawings call
out for either 2500 psi or 3000 psi concrete and the rebar is called out as
either square bar for deformed round bars. Does any know what rebar grades
were used in this time period? I know 40 ksi rebar has been around for a
long time but as grey as my hair is this is before my time. I might add
that this structure is in amazingly good shape with little deterioration.
Goodos for our fathers and grandfathers.
Thomas Hunt, S.E.