Concrete circular Tank

[markmartinfan]

PCA Tank Manual Circular Tanks

Article 18 Temperature

My co-workers tell me this is not a big concern and use silos as an example.

But when I run a FE model for the water tank - I get significant hoop stresses and hoop moments - and I cannot just let this go.

Any experience would be tremendously appreciated.

Thank you,

 

[oneintheeye]

what s the question?

 

[markmartinfan]

Sorry,

The question is do you include thermal loads as a load case - I have been told not required based on experience - but would like to prove this to myself first.

When I preapre a model I get signficant hoop forces and hoop larger than the forces from the water pressure.

Just concerned on how others handle this.

Thank you,

 

[Ussuri]

Is this hot water or is the water the same temperature as the environment? Tanks designed to hold water at ambient temperature are not designed for thermal effects. Once the concrete has cured the walls are the same temperatures (more or less) as the water, as the air. It will be in equilibrium.

However, you will have a temperature differential across your wall while the concrete is curing. This is significant. This will cause the concrete to expand and contract at different rates, at different locations within the wall cross section. This causes the concrete to crack. This must be considered or your tank will leak.

 

[markmartinfan]

Say a typical water or waste water tank

-- no cover

-- no fill

-- 30 ft tall, 100 ft daimeter

-- 100 degree day and water of 70 degrees, outside of wall 100 degrees F plus, inside 70 degrees F +/-.

Is the temperature gradient 30 degrees F or do you also look at a factor "kt" to reduce this as given in ACI 313 - silos - where temperature extremes can be 400 degrees F?

 

[civilperson]

The temperature of the concrete will vary from 70 degrees inside to a little greater at the outside. Not as much as the air differential change in temperature.