When is compression steel stress supposed to be reduced?

[Respawn]

When is compression reinforcing steel in concrete supposed to be reduced? (f's-0.85f'c)?

 

[bugbus]

I don't understand the question but it looks like it's a reduction in the effective steel strength to account for the fact that the gross concrete area has been used?

 

[Respawn]

@gusmurr Yeah, when solving moment capacity using strain compatibility (T=C)

 

[JoshPlumSE]

It's supposed to be done ANYTIME you use that fs in the calculation and that bar falls within the compression block. Otherwise, you're double counting that area.

That being said, it doesn't really matter in a practical sense if you do this or not. You're subtracting out a very small area of the concrete compression block and it is unlikely to significantly affect your calculation. If you're writing a computer program, take this into account. If you're doing quick hand calcs to justify your design or your computer output, then don't bother.

 

[rapt]

You are not "reducing the steel stress".

You cannot count the steel and the concrete it replaces and both existing. So you are actually reducing the concrete area by the area of the steel.

 

[Respawn]

@rapt @JoshPlumSE Thank you so much!