huangyhg

grade of rebar in the 1940's
hello all;
i鈥檓 currently reviewing a concrete floor slab (elevated) from the 1940鈥檚. does anyone have any information regarding reinforcing rebar back in the 40鈥檚? the rebar schedule is calling off 1鈥?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鈥檚 bars are typically 400mpa (60,000psi). what grade would we be looking at back in the 40鈥檚?
thanks,
mark.

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.
mark416:
see attached for various astm reinforcing bar yeilds through the years.
slideruleera:
that is interesting about the square bars.
i learned something new today.
great. thanks for the information slideruleera and lkjh345.
ikjh345: what publication is that from?
thanks again.
mark.
a star for you slideruleera
always wondered why the 1/8" convention stopped at the number 8 bar, just never asked. very interesting.
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
chapter 6 in fema 356 also gives some good historical info.
attached is the publication the table is taken from.
great stuff. thanks a bunch.
mark.

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