Water Tanks on Existing Slab

[someengineer]

Hello,

I was wondering if anyone could please provide me some advice or suggestions.

Our client would like to install 2 flat bottom water tanks (approx. 3m in diameter and 3m high) into an existing building. There is an existing slab on grade within the building (200mm thick) and the client is pushing for us to build up the existing slab to form a pad foundation. Typically we would break out the existing slab and pour an isolated footing for the tank, however I am wondering what the risks may be if we were just to build up the existing slab since the load is relatively small.

I would imagine that there may be increased cracking and settlement around the tank location. Can anyone provide any insight into whether or not this is advisable?

Thanks!

 

[JedClampett]

Run the numbers. Check punching shear (on the existing slab) for different size pads. It's likely to be a small load vs. the slab capacity. Use half the slab thickness if you think the reinforcing is centered.

 

[Akeee]

As JedClampett said check punching shear with the weight of the tank full of water, but be careful if you are in a seismic zone because earthquake will give overturning moment of the tank, moment that will increase a lot the stresses on the edges.

 

[hokie66]

I think we had this question recently. My answer was just to do it. I can't imagine any 200 slab on ground not being able to support a 30 kPa load. But I agree that the tank moving around in the case of an earthquake should be considered.