Concrete barrier for storage of granular material
Concrete barrier for storage of granular material
(OP)
We have some concrete barriers at one of our warehouses that were purchased about 8-10 years ago. The concrete barriers are movable and are used to separate the different granular materials in the warehouse. How would one go about doing a calculation to determine whether these barriers are strong enough to hold back a pile of this granular material. The barriers are an upside down T-shape and I know the properties of the granular material (angle of repose, density, etc.)





RE: Concrete barrier for storage of granular material
For a first order approximation, calculate the force exerted by the granular material as an "equivalent fluid pressure". Consider one foot of barrier length. See "US Steel Sheet Piling Design Extracts" on my website for general information on how to make this calc:
SlideRuleEra.net
To determine the force the barrier will resist consider the barrier to have vertical sides (not true, but a ok for a first order calc). Estimate or determine the barrier weight (per ft. of length) and coefficient of friction between the barrier and the (assumed level) floor. Calculate the force that friction can resist.
Compare the two numbers and see what you get. If the material piled higher than the top of barrier, there will be additional considerations.
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RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
Will they withstand the loading? Don't know. Not sure how they are reinforced.
RE: Concrete barrier for storage of granular material
For the friction calculations, add the weight of the material directly above the barrier's "foot" to the weight of the barrier.
Edit: Ron is right, overturning has to be considered, too. Sliding still may be the limiting value... the calcs will tell.
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RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
I'd consider taking one or two and cutting into short segments to be used as bracing. A few bolts through the brace "T" and the vertical of the main unit. Do some calcs to find the spacing.
RE: Concrete barrier for storage of granular material
1 - a structural wall should be like shown on file "wall Fig 1"
2 - theoretically the ratio between dimensions should be like shown on file "wall fig 2"
3 - hopefully your barriers are not like "wall canal" because the steel reinforcement is not structural but only for handling (they are used as lining of water canal/flume)
I am going to prepare a file excel for calculation as per "wall fig 1" (just few days)
PS : since I am Italian, what is the difference canal - flume ? Thanks
RE: Concrete barrier for storage of granular material
I hope it can help
RE: Concrete barrier for storage of granular material
My concern really is that you won't have sufficient factor of safety and hence whilst it might be shown to have enough friction to stop it moving, any changes, water at the base or perhaps a sudden extra surcharge ( some material being dropped on it), will cause it to suddenly shift and if anyone is on the far side you could get a lot of flow of material.
Hence if you do this I would recommend you add some extra supports attached to the floor and walls to prevent this.
Perhaps talk to these guys - they really seem to know how to do it. Note that their inner toe is much longer than yours. also they look thicker at the base than your and taper a bit more. http://www.hansonsilo.com/silage.php
Not sure how or if they connect the concrete sections together.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Concrete barrier for storage of granular material
Interesting whether failure would be from sliding or overturning... so I performed basic hand / semi-graphical calculations based on some modest assumptions about a (hypothetical) 6' tall barrier with a narrow (2' wide) base:
My results indicate he barrier will fail by sliding at a depth of about 4.0 Feet with fill (assumed to be "Dry River Sand" with a unit weight of 106 Lb/Ft3 and Angle of Repose of 33.7 Degrees).
If the barrier is restrained from sliding, failure by overturning would occur at a depth of approximately 4.5 Feet:
A summary of all the calcs is attached.
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RE: Concrete barrier for storage of granular material
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
I assumed Reinforced Concrete = 150 lb/ft3 as per the example above.
Total width of base = 5'
Base thickness = 6"
Height of barrier = 10' 2"
Barrier thickness = 8.5"
Material density = 57 lb/ft3
Angle of repose = 35 deg
Coefficient of Friction = 0.8 as per the example above
Using this information, I calculated that if the height of the product is 8.2 ft above the top of the base, the overturning SF is 2.12 and the Sliding SF is 1.50. (One thing I noticed in SlideRuleEra's example is you didn't include the small area of the inclined portion of the material in the weight calculation. Otherwise, it was great and easy to follow!)
The only unknown to me remaining is whether the barrier would structurally handle the load. The barrier is not anchored to the ground in anyway.
RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
I checked your calcs and get somewhat lower Safety Factors for both sliding and overturning. You mentioned that "...the height of the product is 8.2 ft above the top of the base". If I'm reading this right, then the depth of the assumed Equivalent Fluid is 8.7 ft (8.2 ft + 0.5 ft base thickness). The product is "pushing" horizontally on the 6" high base every bit as much as the 8.2 ft. high wall. This may be the difference in our numbers.
Compositepro - I believe all the contributors are considering the "Tee" to be rigid and are summing moments about the outside toe.
The Rankine-Coulomb approach that I'm presenting considers the granular product to be a fluid... and to perform like one. To be consistent with other hydrostatic calcs, can't take advantage of any product weight that is not directly above the "Tee".
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RE: Concrete barrier for storage of granular material
Would You be so kind to explain ??
RE: Concrete barrier for storage of granular material
The sixth page of the US Steel document that I referenced in an early post shows how to calculate an "Equivalent Liquid Pressure" (ELP) for an inclined bank to make the calculations exactly the same as for a Level Bank (See fifth page of US Steel reference). On my summaries I noted, without explanation, that the ELP = 73.4 lb/ft2.
The ELP is then used for all of the following calculation: 330 lb @ 3' deep, 743 lb @ 4.5' deep, and 1320 lb @ 6' deep.
Here is the info from the sixth page (with my notes added) and fifth page:
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RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
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RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
RE: Concrete barrier for storage of granular material
1. You mentioned that the barriers were purchased 8 to 10 years ago... not too old. Any chance you can find where they came from and the manufacturer's specs?
2. Have a testing lab use a Rebar Locator to see what is inside. Make appropriate calculations based on minimal sized rebar.
3. The product is light (57 lb/ft3). Set up 2 lines of barriers and fill the space between them with a common, heavier material (say sand). See what happens. If the barriers don't fail, you now have an "ultimate strength". Back figure what loading is acceptable.
Not the best answers, but better than doing nothing.
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RE: Concrete barrier for storage of granular material
Thanks : very easy to use for rough calculation. Regards