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Grain Bin Overpressure Coefficient

Grain Bin Overpressure Coefficient

Grain Bin Overpressure Coefficient

(OP)
I'm designing a 70' tall, 8'x8'square grain bin to hold corn and soybean meal.  I'm having a difficult time determining the overpressure coefficient to use on the bin walls using Janssen formula.  There's some discrepancy between ACI (1991) which tells me to multiply the horizontal pressure by a factor of 3 for H/D>6 and ASAE EP 433 which tell me to multiply it by 1.4 for H/D >2.  Which is the standard design factor? Thanks in advance for your help.

RE: Grain Bin Overpressure Coefficient

Is there a reason the structure can't be round? That just seems like a bad idea to me to try to contain a lot of pressure [e.g. at the bottom of the structure] with a square structure having flat [at least when built] walls. Seems like they would want to bulge out and become round. Therefore, they might as well be made round to begin with, and go with the flow. Silos, grain bins, feed bins and the like are generally tubular.  

RE: Grain Bin Overpressure Coefficient

(OP)
In this case the walls are corregated steel welded to columns to make up the bin.  Basically, I've figured out the section modulus of the bin walls, but I need an appropriate overpressure coefficient to make sure the walls won't buckle under the pressure.   

RE: Grain Bin Overpressure Coefficient

Unless you keep both products moving constantly, you will have problems with bridging, especially with soymeal.

RE: Grain Bin Overpressure Coefficient

We tend to use overpressure factors from ACI 313 as they are more conservative than ASABE yearbook standards values.  We like mass flow bin design for tall small cross section bins, so hopper inclines are steep, etc.

Soybean meal is one of the most difficult materials to for design, construction and operation trouble free bins.  We tend to design square and rectangular bins with corner draw hoppers to help minimize bridging problems...  We also design hoppers with air blast pads to jar materials loose if needed, but then you have to be careful not to aerate the materials.   We do use some vibrators with some materials.

For really basic design information, the Midwest Plan service has some simplified publications. Then go to ACI 313 for more specific design information.

There are tons of books and publications on bin and hopper design but practical experience under an old master designer really helps the most,,,, LOL

r.

RE: Grain Bin Overpressure Coefficient

We are curious about what other engineers use for steel bin roof design loads especially snow uniform and drifted loads.

r

RE: Grain Bin Overpressure Coefficient

Hi there. Try googling carbo steel clad structures.

Colin S
www.hydroponicshop.eu

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