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grade of rebar in the 1940's
6

grade of rebar in the 1940's

grade of rebar in the 1940's

(OP)
Hello All;

I’m currently reviewing a concrete floor slab (elevated) from the 1940’s.  Does anyone have any information regarding reinforcing rebar back in the 40’s?  The rebar schedule is calling off 1” square and round bars.  Were there standards for rebar back then because I have never heard of square rebar.  Specifically, I am looking for the minimum yield strength.  Today’s bars are typically 400MPa (60,000psi).  What grade would we be looking at back in the 40’s?

Thanks,
Mark.

RE: grade of rebar in the 1940's

4
From ASTM A15-39 (the 1939 version of the document) for deformed rebar, yield strengths are as follows:
"Structural" Grade: 33 KSI
"Intermediate" Grade: 40 KSI
"Hard" Grade: 50 KSI

I would suggest using 33 KSI, unless you have reason to know otherwise.

Many rebar sizes were square until the 1940's. In fact, the legacy of that remains in use today with the crossectional areas of larger rebar sizes being fixed and the diameters being back-figured. This is easier to explain with examples, consider the following:

#9 Bar with area of 1.00 sq. in. = area of 1 in. square bar.
#10 Bar with area of 1.27 sq. in. = area of 1 1/8 in. square bar.
#11 Bar with area of 1.56 sq. in. = area of 1 1/4 in. square bar.
#14 Bar with area of 2.25 sq. in. = area of 1 1/2 in. square bar.
#18 Bar with area of 4.00 sq. in. = area of 2 in. square bar.

www.SlideRuleEra.net idea

RE: grade of rebar in the 1940's

(OP)
Great.  Thanks for the information SlideRuleEra and lkjh345.

ikjh345:  What publication is that from?

Thanks again.
Mark.

RE: grade of rebar in the 1940's

A star for you SlideRuleEra

Always wondered why the 1/8" convention stopped at the number 8 bar, just never asked. Very interesting.

RE: grade of rebar in the 1940's

I have a piece of the 1/2" twisted square bar on my deskfrom an old substation constructed in the 1920's.

Mike McCann
McCann Engineering

RE: grade of rebar in the 1940's

Chapter 6 in FEMA 356 also gives some good historical info.

RE: grade of rebar in the 1940's

(OP)
Great stuff.  Thanks a bunch.

Mark.

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