circular concrete water tanks

[sorinro]

I am designing a circular concrete water tank without prestressing. It has 45.00 m in diameter and is partially buried (2.50 m buried and 1.50 m above the ground), so I loaded with temperature only the above ground wall section with a temperature gradient of dT=20 degrees Celsius.
I am using a structural design software and I've got a strange result for hoop forces: from water pressure I have 15 tones (wich is ok) and from temperature I've got 46 tones. An experienced user of this structural software checked my structural model and said that is ok. I don't understand whay the force is so big. I need some guide lines or some links for specialised documentation on temperature design for circular liquid-containing concrete structures.

 

[borjame]

20 degrees C per what? 20 degrees difference in temperature over a mile isn't much stress, but over .001 in will be a lot of thermal strain . . . and therefore stress. Also, an instantaneous temp change from above to below will do the same thing.

 

[JedClampett]

I'm also having problems with your post. For one, you don't give any length units. Is this tones (tonnes) per meter? Per foot? Per inch?
Also, for circular tanks there are two components of loading caused by thermal gradients. There is a hoop component and a moment component. I don't see any evidence that you have a moment on your tank wall.
My advice is to get the PCA publication "Circular Concrete Tanks without Prestressing" and follow it. They have a pretty good section on thermal analysis.

 

[connect2]

Good question, not far off my question wrt, joints in tank walls designed for thermal loads and 'hoop/membrane' stresses in concrete circular tank walls two weeks ago.

Pointed out was ACI 350 and PCA 'Circular Tanks ....' all talk about construction and expansion/contraction joints, infact the minimum steel requirement is based on their spacing .... my query was wrt. transfering these tensile stresses through the 'Joint', the requirements for tensile wall steel exceeding the requirement for min. steel in most cases.

Yes PCA has a fair bit on thermal Gradients and thermal loads, and the thread i started asked the exact same question and you'll see in that thread some useful references wrt to a New Zelander named Priestly.

Where I design the Delta T is -35C to +45C on an annual basis. Somethings got to give.