ACI 350: calculation of z for crack control

[MThomey]

I am working on a wastewater treatment plant, and need to calculate the z-factor to
check my crack control. I'm using the USD method with the appropriate durability factors.
Cracking would appear to be a service level condition, so my question is this:
Even though I'm using USD, may I calculate z using the service load moments in my
tank walls and base? ACI doesn't seem to make this clear in the 350 Code.
Thanks for your assistance.

 

[JedClampett]

I don't have the current 350 at hand. But in the past editions (the ones I'm more familiar with), crack control was strictly a working stress phenomena. So I'm guessing service level loads are appropriate.

 

[PSEPK]

IMHO, yes. Most probably, being a serviceability requirement, ACI 350-06 has based the calculation of z factor on service load stresses, rather than ultimate ones.

 

[dcarr82775]

Yes, service level moments.

 

[MThomey]

Thank you, gents. Your input was most helpful.