Nominal Rebar diameter vs Max Bar. diameter 1

[yaroosh]

Hello Everyone,

I came across SAS dialogue, and I am trying to understand the difference between nominal diameter and maximum bar diameter, can anyone shed some light please? I looked up the definition of nominal but couldn't find any sources. My thoughts are that the maximum bar diameter is nominal diameter plus threading

 

[BridgeSmith]

Nominal just means that's the approximate size they use to designate it. It may not correspond exactly to the diameter anywhere. You're right that the maximum would be to the outside of the threads. The area for the 1 1/8" threadbar corresponds to a diameter of 1.10", but that likely includes part of the thread, so the minimum diameter (at the root of the threads) is probably a little less. I'm not sure why it matters; it is what it is, and the information necessary for design and detailing is given in the table. They come with the nuts that go with them. Unless you're designing them, you don't need to get into the finer details.

Btw, that table is not for rebar; it's for high-strength threadbar, which is a totally different thing.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Ingenuity]

Btw, that table is not for rebar; it's for high-strength threadbar, which is a totally different thing.

The table is only grade 75/80 ksi. High-strength threadbar is typically grade 150 ksi and used in post-tensioning related applications.

 

[BridgeSmith]

The table is only grade 75/80 ksi. High-strength threadbar is typically grade 150 ksi and used in post-tensioning related applications.

Yep, you're right. I guess I should not have called it "high strength". The 75/80 ksi stuff still has the square threads, though, doesn't it?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[JLNJ]

“Nominal” is sometimes used for “regular” rebar because when you get above a #8 bar the actual diameter is no longer the number of 8ths of an inch. While a #8 bar is 8/8 or one inch in diameter, the larger bars correspond to the old square bar cross sectional area. I.e a #9 is 1.00 square inch (exactly) a #10 bar is 10/8 x 10/8 = 1.56 in^2 etc, same as a 1 1/4 square bar.

These threaded bars do not conform to this system.

 

[BridgeSmith]

...the larger bars correspond to the old square bar cross sectional area.

I always wondered about that...

a #10 bar is 10/8 x 10/8 = 1.56 in^2 etc,

It's actually the #11 bar that's 1.56 in^2 (#10 corresponds to 1 1/8" square), but it makes sense that they made the round bars so they had the same area as a square bar, so that when both were in use, the engineer could easily give the builder the option of round or square without it changing the design.

Rod Smith, P.E., The artist formerly known as HotRod10