A15 and A16 Steel Bar Areas

[msquared48]

Analyzing a building built in 1929 with old A15 or A16 steel bars, probably twisted. Symbols look like square bar. Anyone have a table of bar areas for that time if the area is different than just the square of the bar size?

In other words, for a 5/8" square bar (#5 now), is the area .39 sq. inches, or something different? Makes a whale of a difference in the capacity.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[msquared48]

OK, so I did a little more searching online and came up with a from a CRSI publication. It raises more questions though than provides answers...

CRSI Evaluation Report #48 in Table 2 implies that no reduction was given for bar sizes due to the twisting or rounded edges. It also only lists square bar sizes for 1/2, 1", 1.125" and 1.25" bars. There are no area values for 3/8", 5/8", 3/4" or 7/8", implying that these sizes had to be round bars if used (much lower areas). I find that difficult to fathom logically speaking.

The area difference makes a difference in capacity of 20% or more. Anyone ever run into this before?



Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Archie264]

msquared, I don't think I can answer your question but I know that I have run into square bars in the past, both twisted and untwisted. I don't know why you would need to consider anything other than the actual area of the bar, though, as the material is still there regardless of whether or not it's twisted. (Assuming no corrosion, of course.)

Something you might want to watch out for is that placement of bars back then wasn't necessarily what we have now, particularly in regards to stirrups and shear reinforcing, if I'm remembering correctly from one particular beam I saw some years back.

On the other hand I know of a one lane bridge built back in the 1920's that had square reinforcing and it's still functioning fine after all these years and recently some heavy gravel trucks went over it with no ill effect.

 

[Archie264]

Ok, I did a little more looking too. I found a chart from the book "Design" subtitled "Data Book for Civil Engineers, Second Edition", edited by Elwyn E. Seelye, dated 1956. On pg. 1-39 it lists the following bar areas in square inches. (For convenience d = diameter; s = square, my notation):

1/4" d: .05
3/8" d: .11
1/2" d: .20
5/8" d: .31
3/4" d: .44
7/8" d: .60
1" d: .78
1" s: 1.02
1 1/8" s: 1.27
1 1/4" s: 1.56

The only one that surprises me is the 1" square one. I wonder why the area is 1.02 and not 1.00? For what it's worth...

 

[msquared48]

The areas above from Seeyle are for standard round deformed bars. The ones I have are square, either twisted or deformed.

Again, the insinuation from what I have read in the CRSI Publication I posted above from 1924 is that square bars were not available up to 1/2" and 1" or greater on a side, but not between 1/2" and 1". That seems funny since I am getting obvious square bar callouts on the plans I have from 1929.

Something doesn't add up here.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Archie264]

Well, the last three areas are indeed for square bars but granted, they're not between 1/2" & 1".