Circle slap supported by circle beam

[aun]

The problem is how to design a cylinder water tank supported by slab with circle beam around the slab. I heard that the approach called "ring wall" to design the beam but I am not sure what it is and where I can find more information over internet.

Thank you in advance.

 

[aun]

if some given data is missing, please let me know. I really want your help.

 

[Ingenuity]

aun,

i guess it is a concrete tank. if it is a large capacity tank often they are post-tensioned. likewise the tank base slab and ring beam is post-tensioned. i am not sure if you are going to find out too much on an internet search but there some texts/publications available for specialty organisations.

give a bit more detail/s and i may be able to assist further.

 

[aun]

Dear Ingenuity here is some more detail.
The closed circle beam, rectangular section is supported by piers. Its radius is 30 feet. A number of pier is 10 which roughly gives the spacing between piers equal to 18 feet And it's a cast-in-past beam. I have discussed this beam with my friend and he said that "stretch the beam to a straight beam and use the circular distance for the beam length. The trick is you won't have a real edge condition. So your steel would be over design which is good. One thing you have to watch out is the torsion" Is it correct??

 

[srdboyd]

You may want to refer to a book by Warren Young, "Roark's Formulas for Stress & Strain". This is a very good book you should have for your library. The book has many formulas for determing stesses on rings and a varity of other members based on different loading conditions.

 

[ishvaaag]

In any case, a tall ring foundation, or the incorporation of the wall (if stiff enough, namely, a concrete of wall substantial thickness) gives readily to modelization in FEM on the load-sistributing structure and then find likely efforts for a number of hypotheses. Of course any closed form adequate to your structure can also be used even more confidently along sound engineering principles.

 

[RiBeneke]

The analysis of this type of structure is not efficient if you you use simple beam formulas. As ishvaaag suggests, you require a finite element modelling method to obtain realistic results.
If you are using a simplified method, then you must carefully consider the relative stiffness of the components (floor, ring beam and walls) in bending, hoop or sheet tension, torsion (for the curved ring beam) etc. Then you must distribute the forces according to the relative stiffnesses (stiffer member takes more force) and design accordingly. Each member must be designed for its share of gravity and hydraulic pressure forces, therefore analyse forces in 3 directions.

 

[dlew]

What kind of bottom does the tank have? A flat concrete slab or a steel conical hopper?

If it is a flat concrete slab, before designing the ring beam, you need to design the slab. This slab will support the weight of the liquid inside the tank.
Normally, the slab reinforcing steel is placed in two directions, perpendicular to each other. So, the slab will have to span 60 feet at the center. That's quite a span! You may want to consider intermediate beams to reduce the thickness of the slab. A concrete slab poured monolithically with the ring beam would reduce the torsional stresses in the circular beam.

If the tank bottom is a steel conical hopper, then the weight of tank and content will be supported by the ring beam as a uniform load. The analysis could be done with the help of a commercial computer program, such as STAAD. You could design the ring beam by hand too. Conservatively, you could assume the developed arc between piers as the span of a continuous beam to calculate the longitudinal reinforcement and the shear. But for the shear reinforcement you should add the torsional moment due to the curvature of the beam.
AEF