Temperature and Shrinkage Steel

[vincentpa]

For temperature and shrinkage steel, is it necessary to increase the flexural steel in structures such as walls and slabs to account for shrinkage and temperature stresses in the concrete? For slabs, I thought creep offsets temperature and shrinkage but what about concrete walls in a tank? Can anyone explain better? It is hard to find references for design for temperature and shrinkage.

 

[vincentpa]

What about in applications when the concrete is subject to direct tension such as hoop stresses in a wall? I would think the tension steel for the hoop stresses would be additive with the shrinkage and temperature steel.

 

[gotwood]

I am a pretty green engineer so dont take anything for granted. My understanding is that you just design the slab/wall to whatever loads you have. Then look a ACI 7.12.2.1 and make sure your current reinforcement is more than the rho given on 7.12.2.1. If its less, then increase the steel.

 

[miecz]

I think gotwood got it right. If you're dealing with a liquid retaining tank, be sure to check 7.12 from ACI 350, not ACI 318.

 

[BigInch]

A long time ago Fy was limited to 40 ksi to prevent excessive tension ring crack formation. I'm not sure if its still the same.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com

 

[MotorCity]

Temperature steel is for shrinkage cracks, flexural steel is to resist applied loads. They are used for completely different purposes so be sure not to confuse them. While its true that temperature steel may contribute to the strength of a member, that is not its intended purpose. The amount of flexural steel required is based on concrete mechanics while the amount of temperature steel is based on the proportion of concrete being placed.

 

[BigInch]

Absolutely, but talking about the (evolved thread) tank design provision, is there any practical difference when you talk about cracks in a tank, as you don't want either one and there is (was) a specific Fy limitation just for the purpose of crack control (perhaps in no way temperature related). I think the Fy=40 provision may be in the ACI 350.

BigInch-born in the trenches.

http://virtualpipeline.spaces.msn.com