Slab on Grade with Tank Slab
Slab on Grade with Tank Slab
(OP)
I was asked to do a slab and footing design for a building addition that will house a 4300 gallon equalization tank. The addition is 14'x20' and the tank takes up part of the building with a footprint of 8'x12'. The architect proposed a 4" concrete pad atop the building's slab. My supervisor thinks it should be a floating pad separate from the building's slab. Is this common procedure? I don't see a small slab like this helping anything if it isn't composite with the floor slab.
Also, what is typically done when a tank is on part of a building's slab as far as bending? I'm more of a bridge guy so slab on grade design isn't my forte. I've found the TF 705-R-03 Slab on Grade Design by WRI. It mostly covers design on clay soil, whereas mine is strictly on sandy soil. I have the crack control down but worried about the large load from the tank. Looking for a little guidance ;)
Also, what is typically done when a tank is on part of a building's slab as far as bending? I'm more of a bridge guy so slab on grade design isn't my forte. I've found the TF 705-R-03 Slab on Grade Design by WRI. It mostly covers design on clay soil, whereas mine is strictly on sandy soil. I have the crack control down but worried about the large load from the tank. Looking for a little guidance ;)






RE: Slab on Grade with Tank Slab
RE: Slab on Grade with Tank Slab
Once you seperate the two, then you can design the portion under the tank as a regular concrete footing, and the slab as regular floor slab.
Not knowing the situation exactly, you might consider seperating the tank footing from the slab with 3/8" or 1/2" expansion joint material caulked at the top.
For the tank footing I would place the top 4" above the top of the adjacent slab to make a 'house keeping' pad look. It also will somewhat disguise a bit of settlement by the tank footing in the future.
Is your building heated? If frost heave might be a problem in an unheated building, then I would sink my footing down to frost depth. If the building is heated (or are you in a place where frost heave is not a problem), then I might think about say a 16" thick footing. 4" above the floor slab elevation, 12" below.
Just my thoughts, not being fully aware of the exact situation.
RE: Slab on Grade with Tank Slab
So based on your guys recommendation, the tank's slab should be separated from the building's slab and the tank's slab will have footings on the perimeter as well. The slab will be elevated the 4" so any settlement will be not as noticeable. My calculated pressure on the slab from the tank is 400psf when full. Again, thanks for helping this young engineer ;)
RE: Slab on Grade with Tank Slab