Design of Steel Bins Gaylord and Gaylord 1

[CardsFan1]

I am trying to determine the stresses in a bin wall. I have a copy of Gaylord and Gaylord "Design of Steel Bins for Storage of Bulk Solids". I am hoping that there is an expert out there that can answer a question for me. In example 5-3 the pv = density x depth, which is what I expect. But in example 5-1, there are tabulated values of pv that equates to about half of the density x depth.
Question 1, What is pv in Ex 5-1?
Question 2, How do you use Table 5-1 to determine f(u'Ky/R)?

 

[SlideRuleEra]

CardsFan1 - Agree with you, this section is confusing. Appears the discrepancy may be caused by using different sets of equations for each of the examples. The reason different equations were selected may have to do with the geometric proportions of the bins.

Bin in Example 5-3 is "tall" (18' +) compared to it's diameter (3' +), a height to diameter ratio of about 6:1

Bin for Example 5-1 is more shallow, 57' + high compared to 16' + diameter. Ratio of about 3.6:1

Reread Chapter 5 with this in mind to see if that makes a difference. Also, can't rule out the materials filling bins in the examples having very different properties... see if that influences which set of equations is selected.

http://www.SlideRuleEra.net

 

[CardsFan1]

SlidRuleEra,
Thank you for the response. After I spent a couple of hours with this and posted the questions, I remembered that I downloaded a standard from ASABE, "Loads Exerted by Free-Flowing Grains on Bins". I think this is a more straight forward procedure. I will let you know how it all works out!

 

[JStephen]

First off, I don't have the book available, have used it in the past.
Your pv = density x depth is only true if you're neglecting friction on the sidewalls.
There's one section in that book where they use one set of coefficients to derive the pressures. Then they turn right around and say "But so-and-so recommends THESE coefficients" and if you check, that gives you completely different numbers. So be very wary of trying to get that to three decimal places like you would with a liquid.
Some years back, I took the ASME short course in flow in bins. The first lesson learned there is that if you don't have actual test data for your particular product, you don't necessarily know what's going on in there.
An observation from experience: Juggling those factors around gives you more friction, more shell compression, but correspondingly less hoop stress. For a large silo, you need to look into that for an economical design. For a small silo, you can check compression assuming all the product sticks to the shell, check hoop force assuming the product acts like a liquid, and reality should be somewhere in between those extremes. If that gets you close enough, though, it's a quick and simple way to check the shell design.

 

[dhengr]

CardsFan1:
I don’t have that Gaylord and Gaylord book, so I can’t see the problems, formulas or verbiage around them. But, I’ll bet the 18’ high by 3’ dia. tank will experience bridging or arching of the bulk solids loading. Which leads to the bottom 3,4-5’ being removed in a fairly normal fashion, but the material above there hangs up, on the tank sides, in a conical arched shape, on the underside.

 

[Agent666]

Also the deeper the material is its is more likely in a small tank/silo to get 'silo' pressures (Janssen's equation) whereby the horizontal pressures reach a steady state pressure and no longer increase with depth (similar to what dhengr is discussing).