Monolithic Concrete Tanks.
Monolithic Concrete Tanks.
(OP)
I have been asked to design a large, 44m dia, concrete tank using monolithic construction, i.e. no joints in the floor or walls. I understand that high reinforcement ratios will be required to control cracking.
Does anyone know of useful references for designing tanks like this?
Does anyone know of useful references for designing tanks like this?





RE: Monolithic Concrete Tanks.
What is its use? Water, grain, cement, other?
What is its height?
How will it be constructed...slipforming to achieve monolithic requirement.
Have you considered post-tensioning?
ACI has several documents on circular tank design.
RE: Monolithic Concrete Tanks.
No post tensioning, reinforced only.
Shrinkage compensated concrete may be considered.
Walls will be several meters high, formed in a number of lifts. There can be construction joints but no dowelled or keyed joints.
RE: Monolithic Concrete Tanks.
RE: Monolithic Concrete Tanks.
By the way, why a monolithic tank? It may not be the most economical or serviceable in all situations.
Just some thoughts to consider.
RE: Monolithic Concrete Tanks.
The current thinking seems to be that it is better to build a monolithic structure and save on problems with joints, even though the reinforcement will be a lot higher. So I've been told.
I will have a look at "Circular Concrete Tanks Without Prestressing".
Thanks for your help.
RE: Monolithic Concrete Tanks.
If you are having problems with joints, the contractors are not doing them correctly. Our company designs may round concrete structures every year and leakage is not an issue.
If the client will not budge on this, I'd document it as well as possible for future reference. I'd also make sure to have a section on epoxy injection of concrete cracks in the contract documents.
RE: Monolithic Concrete Tanks.
The reinforcement needs to be sufficient to limit shrinkage cracking to 0.1mm.
The theory is very simple
The tensile strength of the reinforcement must equal the tensile strength of the immature concrete so that when the concrete cracks on drying the reinforcement carries the same load as the concrete can exert in tension due to shrinkage.
The crack width is dependent on the crack spacing. And if you consider that the reinforcement is carrying full tension at the crack and zero tension at mid way between the cracks the it is apparent that the crack spacing will be twice the bond length.
The simple answer is you need small diameter bars (which have a shorter bond length) at close spacing to limit the crack width.
British Standard 8007 for water retaining structures is what we use
The minimum of reinforcement = BxD x fct/fy
Fct = strength of the immature concrete in tension.
Fy = strength of the steel
The crack spacing S= fct/fb x bar dia/2xp
P = ratio of steel area to concrete area
Fct/fb = ratio of tensile strength of the immature concrete/to bond strength (Usually about 2/3).