Precast elements in an agricultural facility

[MrEngineerUS]

I'm looking at analyzing some precast elements that are being used in a below ground tank used to hold manure. The livestock walk on the precast slatted panels and the manure finds its way into the under barn tank. Technically, the precast beams/column/panels are not exposed to weather but I would consider this an environment where the more conservative limits on clear cover should control. Anyone disagree?

 

[hokie66]

That sounds to me like a very severe environment.

 

[MrEngineerUS]

That's what I was thinking but to be honest my knowledge of the corrosive nature of farm animal waste is lacking. Per ACI318 table 4.2.1 I would use the following categories (assuming what I've been able to find out about the sulfate content of animal waste from Google):

Wall Panels - F2,S2,P1,C1
Beams/Columns/Slab Panels - F0,S2,P0,C1

From this I think I could back-up my using the more conservative limits on clear cover. Not sure if the suggested limits for more corrosive environments are necessary though (per ACI R7.7.6).

 

[wannabeSE]

I would look at ACI 350, Code Requirements for Environmental Engineering Concrete Structures. Tanks are not in the scope of ACI 318-11 per §1.1.10.

This Code does not govern design and construction of tanks and reservoirs.

 

[MrEngineerUS]

Yes, I'm familiar with ACI 350. This particular type of facility is not a "tank" necessarily. More of a basement for a barn that stores animal poop. In addition, the agricultural standards specify that ACI 318 is to be used for design.

 

[KootK]

I agree with the corrosion potential of the environment. I once inspected a chicken storage structure where all of the poop just dripped down through the cages into the supporting floor framing. After only a short time, it looked like something out of a sci-fi movie. Like it had been soaking in nuclear waste or something. Your weak points will likely be connections if any of them are in the line of fire.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.