Allowable reinforcement tensile stress

[PEin2010]

ok I know this may be a very basic question, but for Grade 60 steel reinforcement, the Fy or the minimum yield strength = 60 ksi, how is it that the Fs = 24 ksi? Where does the 24 ksi come from?

I know I'll probably have an 'aha' moment when I find the answer, but for now, It's just blowing my mind that I don't know this!!!!

Thank you!

 

[IL-SE]

ok I know this may be a very basic question, but for Grade 60 steel reinforcement, the Fy or the minimum yield strength = 60 ksi, how is it that the Fs = 24 ksi? Where does the 24 ksi come from?
I know I'll probably have an 'aha' moment when I find the answer, but for now, It's just blowing my mind that I don't know this!!!!

Thank you!

fs is for the alternate design method, which was in the 99 code (appendix A), but then removed in the later versions. There is a provision in the new codes that you can still use it, but it's not widely used. There isn't an equation in the code, they just give you the values. fs (fy=40 ksi, 50 ksi)=20 ksi and fs (fy=60 ksi)=24 ksi. I don't think I've ever used the alternate design method in practice. Is there a reason you aren't doing LRFD? I'm pretty sure all the concrete questions on the PE are LRFD. Only steel and wood are offered in both formats.

Keep in mind that fs is also used to represent the actual stress in the reinforcement (chapter 10).

 

[PEin2010]

ok I know this may be a very basic question, but for Grade 60 steel reinforcement, the Fy or the minimum yield strength = 60 ksi, how is it that the Fs = 24 ksi? Where does the 24 ksi come from?
I know I'll probably have an 'aha' moment when I find the answer, but for now, It's just blowing my mind that I don't know this!!!!

Thank you!

fs is for the alternate design method, which was in the 99 code (appendix A), but then removed in the later versions. There is a provision in the new codes that you can still use it, but it's not widely used. There isn't an equation in the code, they just give you the values. fs (fy=40 ksi, 50 ksi)=20 ksi and fs (fy=60 ksi)=24 ksi. I don't think I've ever used the alternate design method in practice. Is there a reason you aren't doing LRFD? I'm pretty sure all the concrete questions on the PE are LRFD. Only steel and wood are offered in both formats.

Keep in mind that fs is also used to represent the actual stress in the reinforcement (chapter 10).

This question was concerning masonry. Does masonry use ASD?

 

[IL-SE]

Sorry been doing a lot of concrete design at work lately, so I have ACI on the brain.

Masonry is ASD. The Fs values are similar to those I listed for ACI and given in 2.3.2.1. It's just the given values rather than a formula.

 

[playboyman007]

ok I know this may be a very basic question, but for Grade 60 steel reinforcement, the Fy or the minimum yield strength = 60 ksi, how is it that the Fs = 24 ksi? Where does the 24 ksi come from?
I know I'll probably have an 'aha' moment when I find the answer, but for now, It's just blowing my mind that I don't know this!!!!

Thank you!

It's pretty much coming out from the code (MSJC). Grade 60 steel has an Allowable steel stress of 24000 ksi and Grade 40 has an Allowable steel stress of 20000 ksi.

Ahhh...takes me back 2 years ago when I was taking Reinforced Masonry Design.