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Hay bale #7770 07/26/01 05:44 PM
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Ken Hume Offline OP
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Can anybody please advise me the size and weight of a standard rectangular type hay bale. I am trying to figure hay mow loading with a full loft.

Regards

Ken Hume

[This message has been edited by K F Hume (edited 07-26-2001).]


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Re: Hay bale #7771 07/26/01 11:04 PM
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I believe it's 40 lbs per bale. But others will probably have more answers. Good luck, Jim

Re: Hay bale #7772 07/29/01 02:49 PM
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According to ASCE 7-98, Minimum Design Loads for Buildings and Other Structures, the minimum live load for hay and grain storage is 300 lb/sq ft (14.4 kN/sq m). This doesn't answer your question regarding the density of a hay bale, but it might be a start.

Re: Hay bale #7773 07/30/01 06:46 AM
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Ken Hume Offline OP
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Dear Dick,

You have actually answered the question that I was getting around to asking but in an indirect sort of way. The magnitude of the code loading takes me by surprise. I wonder if it is realistic to apply such a heavy loading across the entire hay mow floor given that it will carry full height loading only over the central section and less towards the eaves due to the sloping roof ?

Regards

Ken Hume


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Re: Hay bale #7774 07/30/01 02:46 PM
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Ken,

The load is quite high, probably because no one knows a priori the geometry of the structure that will support the load or the exact nature of the load. If you know the density of the hay, then you can account for the limited headroom along the sides and possibly reduce the load. The load standard has a footnote that might tickle you: "Use weight of actual ... stored material when greater." Yea, no kidding! Basically, I think that you are back to weighing and measuring a bale. You might want to soak it with water first!

Dick

Re: Hay bale #7775 07/30/01 07:17 PM
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Ken Hume Offline OP
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Dear Dick,

I used your 300 lbs / sq ft figure today in my model and got really alarming results - 20" deep beams.

I then did a quick check assuming that a hay bale is 2 x 2 x 4 and weighs 50 lbs and I got a remarkably good comparison with your code figure loadings.

This led me to question why the typical 8 x 8 scantlings is so common in North American mid west barn frames.

The answer might be simple. I guess that the hay bale is probably a fairly recent invention and I would surmise that most barns were built to be loaded from the ground floor to the roof and did not necessarily have a fixed mow floor. I have seen many pictures of round poles which are simply laid across the mow beams and this might explain how the old barns did not need to be built to such a demanding standard since most of the weight must have been bearing on the ground floor and of course there would also have been an internal wall pressure as well.

I managed to solve my problem using cleverly positioned bracing and also narrowing the main mow beam span which helped reduce horizontal shear from 120 to 60 psi and also depth of beam from 20" to 12".

Now I know why those Dutch barns have such deep swing beams. It does not appear to be overdesign.

I will weigh a hay bale tomorrow at my friends farm.

Does anybody have any thoughts on these observations.

Regards

Ken Hume


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Re: Hay bale #7776 07/30/01 10:03 PM
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Hey Ken and Dick

I've tried to check hay density figures and have found that results will vary. The heaviest per cubic foot bale offered for sale was a high grade alfalfa bale 15" x 18" x 36" weighing 80 lbs. That is 14.2 lbs. per cubic foot. Hay, as a commodity, is sold by the ton and to grade standards. Farmers engaged in the sell of hay as a commodity should know the bale weight. Lacking input from a supplying farmer, a local farmers co-op should be able to give a good idea concerning your local market. Grain density is much greater, wheat berries weigh about 48 lbs/cubic ft.

The 1842 Penn. style barn I am currently working has floor joist hewn on opposite sides 8 inches deep with a min 10" width on average 36" centers spanning 9' to 10'. Longitudinal beams are 10 x 12 with posts every 10 feet.

The standard of 300 psf min. turns up in a 1958 handbook.

Re: Hay bale #7777 07/30/01 10:23 PM
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Roger Nair Offline
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Sorry, bale size I stated is correct the weight should be 70 lbs or 12.4 lbs/cubic ft.

Re: Hay bale #7778 07/31/01 04:06 PM
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Although I do not consider myself an expert, I have 12 years experience as a structural engineer and 6 years experience designing and building timber framed barns. Based on my experience, I feel a reasonable number to use for typical timber framed hay loft designs is around 60psf. Here is why. Our typical barn is a 24x36 bldg (864 sqft of loft) with a 4ft-knee wall. This building can accommodate approximately 500 bales of hay, which equals 0.58bales per sqft. Or, at 50# per bale, around 30psf. I like to design lofts for around 60psf, but I'm not uncomfortable with 50 or even 40 psf. A building with more overhead or large haymow would require a similar evaluation. In order for a 24x36 building to approach 300psf of loading, it would have to hold 5,184 bales of hay. That's a lot of hay. 300 psf seems excessive for all put the largest commercial hay storage facility. Any thoughts?

Re: Hay bale #7779 08/01/01 01:47 AM
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From what I've read in the last day or so about hay density, it seems that 14 pcf might be a bit high. But let's assume that is a reasonable number. If the stack could be limited to a 4 ft. knee wall height, then a number like 60 psf is appropriate. However, I would not feel comfortable with that value. Hay stacks routinely reach 8-10 ft in height. 300 psf would require a 20 ft stack -- seems a bit unreasonable. Nevertheless, I would be inclined to design for a relatively full loft, assuming that the farmer has mechanical means to fill it.

Interesting question! Thanks Ken. I'll pose it to my structural analysis class next semester and see what they do with it.

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