Historic Concrete Reinforcement cca. 1908

[LicensedToPEe]

I’m working on a building constructed in 1908 (the historic Univ. of Chicago campus) and I have encountered a strangely called out rebar in the floor concrete T-sections:

3-1/2”x3”x7.8# T bar. (Graphically shown as a rectangular plate.)

Does anyone have any idea how to figure out the actual steel area OR what this rebar actually looks like?

Thanks!

 

[msquared48]

Based on 490#/ft3, I calculate about a 3/8" thick plate.

As for what the "rebar" looks like, the nomenclature is a "T" bar, so I would assume that the shape is just that, a "T".

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[LicensedToPEe]

Msquared48,

Do you mind sharing as to how you calculate the 3/8" plate? What dimensions are you using to arrive at this thickness. I am not following based on your justification given above...

Thanks,

 

[msquared48]

I am assuming 3" + 6.5" - .25" initial plate thickness assumption for the effective plate width.

The equation becomes 6.25tX490/144 = 7.8, or t = .36

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[woodman88]

This web site talks about early 1900 concrete buildings. Not sure if it will help. Such as "Between 1900 – 1940, many patented systems were applied to detailing and reinforcing bars that are now ineffective by today's standards."

Garth Dreger PE
AZ Phoenix area

 

[paddingtongreen]

I think the "T" means twisted. I think there are three bars, each being 3" flat bar weighing 7.8lbs, a little more than 3/4" thick, twisted.

I haven't seen flat bars twisted before, but I know that they used to twist square bars.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[LicensedToPEe]

I will be making some "lower bound" estimates on the amount of steel. I've looked in some old literature and woodman88 is right, there are too many patented systems. I'm taking a 3-1/2" x 3/8" plate as my "As" and ignoring the vertical 3" x 3/8" 'T' portion, to be conservative.

Thanks, all!

 

[SlideRuleEra]

See the attached document for guidance on evaluation of reinforced concrete from this time period.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[LicensedToPEe]

SlideRuleEra,

I’ve gotten papers from you before and again, you come thru. Thanks! The paper is a keeper…

 

[JStephen]

I've seen old concrete that had railroad rails sticking out of it, used as reinforcement. There's not much telling.