PCA Circular Concrete Tanks
PCA Circular Concrete Tanks
(OP)
Help! I'm analysing an existing circular tank, open top with base fixed to the bottom slab. In "Circular Tanks without Prestressing" by the PCA, it is recommended (section 13) to combine and distribute induced moment from the base slab with moment in the wall in order to accurately predict maximum ring tension. However, for the life of me, I cannot visualize how moment in the base slab could exist simultaneously with moment in the wall - if the tank is full, the wall has moment and ring tension but the base slab is everywhere loaded in opposition to the soil reaction; and if the tank is empty the base slab will have moment but the wall will not be loaded. The PCA example is short on delivery of how the base slab in the example has moment...
I know you guys who do tanks everyday know the answer to this one - please share.
Thanks!
I know you guys who do tanks everyday know the answer to this one - please share.
Thanks!






RE: PCA Circular Concrete Tanks
RE: PCA Circular Concrete Tanks
Thanks!
RE: PCA Circular Concrete Tanks
RE: PCA Circular Concrete Tanks
RE: PCA Circular Concrete Tanks
Jed, thanks for looking into this for me. I'm trying to get a copy of Batty's tank book, but my deadline for this study phase will overtake bthat effort. Any insight you can lend would be greatly appreciated.
Thanks again...
RE: PCA Circular Concrete Tanks
We design for the moment from Table A-2 and that's pretty much it.
RE: PCA Circular Concrete Tanks
Thanks again...
RE: PCA Circular Concrete Tanks
The way I understand it you have three options at the wall base connection Sliding, all in hoop tension in the wall
Pinned base, water resisted by wall tension and vertical moment in the wall. The moment is obviously zero at the bas and consequently no moment in the base. The last option is a fixed base and the one you are concerned about. The wall moment is reduced as it is fixed at the base, this moment must go into the base. The base must therefore be big enough to develop that moment otherwis it will rotate a little bit and act as a pin.
The easiest way to analyse the wall would be to model it as a beam on elastic foundation with the base stiffness equivalent to the wall stiffness. You can then play with the support fixity and see how the moment and hoop force vary