Tank Foundation Design to AWWA D103-97 Type 6 1

[YewSeing75]

Hi,

I am designing a 100 ft wastewater tank to API650 and intended to omit floor plates for cost saving purpose.
AWWA D103-97 do provide such design with concrete slab foundation as Type 6 foundation.

My doubt, can I mix the design, with welded shell design to API 650 and foundation to AWWA D103-97?

Please advise. Thank you.

 

[JStephen]

It can be done. The resulting tank doesn't comply with any particular tank standard. There is not any standardized way to make the connection between the shell and the concrete bottom, so no guarantees that the joint is watertight, either.

 

[IFRs]

Saves cost now, costs way more later. In my opinion, perhaps not the best choice.

 

[bimr]

You should be using AWWA D100 Welded Steel Tanks for Water Storage

The industrial water treatment companies use this type of design. There is an ringwall angle embedded into the concrete that the tank wall is welded to.

The Contractor shall design the tank, appurtenances and concrete ringwall tank foundation in accordance with AWWA D100, including Appendix C.

Of course, the wastewater needs to be compatible with the concrete.

 

[MJCronin]

I agree with bimr....

Why would you not use AWWA D100 ????

This is a decades proven set of rules that will ensure a reliable tank at absolute minimum cost.

What is your motivation to try to pick and chose what you want from other sets of rules ?

(Wait... ! wait.... ! are you going to tell me that the client is somehow insisting on API-650 ???/??/????)

MJCronin
Sr. Process Engineer

 

[YewSeing75]

Hi MJCronin,

The original design was to API 650, but would like to bid for a new job at lower price. Found AWWA D103 do provide such option but not so sure about D100. Thanks for the advice.

 

[YewSeing75]

Hi IFRs,

Can you please elaborate more why does it cost more later? Thanks

 

[JStephen]

AWWA D100 does not include composite steel-concrete construction, either. Stresses with AWWA D100 are a little lower, but overall, won't change the tank much.

Hopefully, if the bottom plate is being omitted, the tank is not on a ringwall.

 

[bimr]

IFR is adding some caution because you have only discussed saving money. You have not addressed what fluid will be in the tank, the height of the tank, the risk of failure of the tank, etc.

Agree with JStephen, that AWWA D100 tanks have to have steel bottoms. You would have to go with the bolted tank foundation to omit the bottom if you were to require that the tank met a particular code. Bolted tanks are probably less expensive than a welded tank anyway. And field painting is not required.

As my previous post indicated, that are industrial water treatment companies that omit the steel bottom. A non-code design.

Not sure why you would delete the bottom anyway as a steel bottom is less expensive than a concrete bottom, for a 100' diameter tank.

The most common foundation for a steel water tank is the concrete ringwall and the tank rests on compacted fill.

 

[IFRs]

I have seen concrete bottoms for steel tanks and there was always corrosion at or near the concrete-to-steel interface. They experience different thermal expansion, when steel corrodes it expands and spalls the concrete, etc. It was economical for the project but costly in the long run.