PCA Circular tank Design

[aalmasri]

Hello All
I was going through the PCA circular tank design, and I noticed it calculates the ring steel by dividing by 0.9fy, while in some other places, it states that the steel stress should not exceed a specific value fs (20ksi for grade 60 steel and 14ksi for grade 40 steel). does anybody know a reason for this confusion?

in the old version of this document, As was T/fs, but in the newer version it is T/0.9fy. Am I right or what?

Thanks

 

[JAE]

The older one appears to be ASD while the newer is LRFD.

Old: Service level loads with allowable stresses.
New: Factored loads with nominal capacities (phi x max. strength)

 

[aalmasri]

Thanks JAE
After checking, both documents used factored load...

 

[JAE]

Well I would question that. The first of the two examples you posted uses the term "allowable" which is never used with factored loads.

 

[aalmasri]

You were right, the old document used service loads, while the newer document used the factored load.
What confused me is ACI350, where in chapter 9 it discusses the load combinations and load factor, and then limits the stress to fs. I dont know if I should go with fs, or 0.9fy?