Columns supporting vertical cylindrical tank?
Columns supporting vertical cylindrical tank?
(OP)
Does anyone know of any reference material for the design of columns supporting vertical cylindrical tanks (or hopper bottom tanks). I have the reference "Design of steel bins for storage of bulk solids" by Gaylord & Gaylord, but they only discuss the columns briefly and do not deal with any unbraced columns.
I'm looking at at tank/bin with a hopper bottom, and I want to analyze the bin with only using radial bracing from the discharge (ie. no x-bracing or anything along the perimeter of the column circle)...I can do this in RISA but I can't find any way to back up the work with hand caclulation checks...
Anyone have any ideas?
Picture attached:
htt p://files. engineerin g.com/getf ile.aspx?f older=5e35 01fb-2961- 4de3-95f0- 7f87d1db19 83&fil e=risa_hop perbin.png
I'm looking at at tank/bin with a hopper bottom, and I want to analyze the bin with only using radial bracing from the discharge (ie. no x-bracing or anything along the perimeter of the column circle)...I can do this in RISA but I can't find any way to back up the work with hand caclulation checks...
Anyone have any ideas?
Picture attached:
htt






RE: Columns supporting vertical cylindrical tank?
I will say that i'm not sure that, in your sketch, you have accomplished anything. I don't think that you have created an effective diaphragm at the bracing level. Even if you did, I don't think that you decreased the column cantilever length. You may have only assured that all columns deflect equally.
RE: Columns supporting vertical cylindrical tank?
RE: Columns supporting vertical cylindrical tank?
RE: Columns supporting vertical cylindrical tank?
BA
RE: Columns supporting vertical cylindrical tank?
Depending on the code you need to comply, you may have wind, seismic or lateral stability loads (I would add some kind of accidental torsion) to apply onto the bin. I guess you will come to the same conclusion after the analysis.
Regards,
Ibrahim Demir
RE: Columns supporting vertical cylindrical tank?
You could fix the bases and make the columns larger and try doing a cantilever column system. I would probably fix the bases regardless with your condition.
RE: Columns supporting vertical cylindrical tank?
RE: Columns supporting vertical cylindrical tank?
designing it this way, though, for the following reasons:
Column Bracing:
1. Using a common brace point for all the columns would
eliminate any redundency in the design.
2. The cone hopper would certainly be stiff enough to
provide bracing for the columns but I feel that to
activate that stiffeness one may require too much lateral
displacement of the cone and cast doubt on it's
effectiveness as a brace point.(It's not a hard point)
3. Any deflection of the cone from it's own loading would
be transferred to the columns with unintended
consequences.
Lateral Loading:
1. As pointed out by the other comments,it does not provide
a mechanism for transferring lateral loads to grade and
therefore would be unstable.
I have used a ring girder, built into the bottom of the
tank and made a moment conn. of the columns to the girder.
Better still, as was pointed out, run the columns up the side of the tank a certain distance and accomplish the same
thing.
Probably, the simplest and most effective is to use x-bracing.
Still, it is an interesting concept and brings up an
interesting question. Is using a common brace point for all
the columns a wise idea.
RE: Columns supporting vertical cylindrical tank?
If the columns are restrained at the top, bottom or both, the structure can be made stable.
BA
RE: Columns supporting vertical cylindrical tank?
The base plate is anchored to concrete with expansion bolts, but I still have always assumed a pin connection.
RE: Columns supporting vertical cylindrical tank?
RE: Columns supporting vertical cylindrical tank?
What type of foundation do you use? Does this foundation cause large differantial displacement under the base plates? If so how do you overcome that? If you did not consider any of these you must have very thick slab that connection the columns, and under the slab is well prepared for the uniform load and displacement under the column bases by geothechnical and civil engineers.
I had an experience that the tank was leaning one side during the filling for hydrotest due to the lack of geotechnical investigation.
I would still not connect the cone hopper lower end to the columns due to the expected load in the hopper, thermal expansion/stresses between the hopper and columns. Depending on the connectivity of the braces onto columns and the hopper, columns may be under lateral loads as well. Does your model considers all these actions may be required during the operation with environmental loads and at rest?
Hope it helps.
Regards,
Ibrahim Demir
RE: Columns supporting vertical cylindrical tank?
I am sorry, but I did not follow the argument of saplanti. Perhaps he could elucidate. Why would anyone consider large differential vertical displacements between columns? It is normally assumed that the foundation is unyielding. If not, then I would agree that the problem becomes much more complicated.
BA
RE: Columns supporting vertical cylindrical tank?
RE: Columns supporting vertical cylindrical tank?
Although the columns are on the ring foundation with suffient thickness, if the geotechical work is not done properly and the soil sattles unexpectedly you still may have problem by loading the columns unevenly and with the second order effect due to uneven settlement. This can be seen clearly during the test or during the loading the tank. If the settlement continues and does not correct itself under the loading you may really have problem.
You had better get foundation data from the civil/geotechnical department just for the confirmation that you have no problem with the foundation settlement/uneven settlement/differantial settlement.
Hope it clarifies.
Ibrahim Demir
RE: Columns supporting vertical cylindrical tank?
The OP stated:
You cannot do that. With only radial bracing, the structure is a mechanism. A ring beam however, moment connected to the top of each column constitutes circumferential bracing and prevents the structure from being a mechanism.
Whether or not it is advisable is another matter.
BA