Use of ACI 350 versus ACI 318 for Design of water tank slab

[Berniedog]

We are designing concrete slabs for a Contractor that uses a International tank manufacturer. This tank manufacturer will not design any foundation unless it is just a standard simple foundation. SO this contractor asks us to design the non-standard ones.

Lately, this tank manufacturer is just using ACI 318 for their design and not ACI 350. SO this contractor doesn't want me using ACI 350. I believe that these tank slabs should use ACI 350 to keep the slab leak proof since there is not a bottom in the tank.

My client does not want to spend the extra money for the S&T steel. What do you think?

 

[JAE]

Perhaps run away?

The client should be told the risks of not providing a proper design and assume all risk/liability for it.
Unfortunately, shedding the liability back to the owner where it belongs is a very difficult thing to do.

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[EDub24]

Design for 350 but just state 318 in the documents? Besides requirements for the concrete mix the main difference I typically see is the increase in flexural steel and shear reinforcement from the durability factor and a cap on the max spacing of bars (12” I believe). ACI 350 was based off ACI 318-02 so in some cases it’s outdated.

 

[JStephen]

I would think the tank manufacturer would want the final say on the water-proofing aspects of the construction; it seems odd that they would just leave that to "whoever".

Several years ago, there was a tank failure of a sizeable tank south of Dallas when the floor slab failed and it leaked enough to wash the soil out from under it- so yes, it can be a problem.

 

[TehMightyEngineer]

I wouldn't lead them to believe you designed it for 318 and not 350, but otherwise agree with edub; the costs for you to go to ACI 350 are going to be small and it's totally warranted for this.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[Berniedog]

Thanks all. Good comments. In talking with hte Contractor, they have built over 4000 slabs for tanks and have good success with ACI 318. They are going to send me an email releasing me from ACI 350.

 

[MotorCity]

Only the AHJ can waive requirements of the applicable building code. Neither the client nor the owner can grant exemptions.

Sounds like there are 4000 slabs out there somewhere that don't meet code, don't buy in to the "that's the way we've always done it" mentality

 

[JoelTXCive]

I'm confused. Is this a steel ground storage tank sitting on a concrete slab?

If that is the case, then I would think ACI 318 would be fine.

Scratch all of the above........i just saw that there is no bottom to the tank. Yes......you definitely need ACI 350.