Lateral Force From Stacked Pipes
Lateral Force From Stacked Pipes
(OP)
I've got an analysis task to evaluate a pipe storage system at a tube mill. The basic rack geometry is two vertical posts extending up from a horizontal wideflange beam at the base. Think of "U" shaped frames spaced regularly with steel pipes stacked directly on top of one another within these frames between the vertical rack members. My question is what is the lateral force produced by a stack of pipes? Pipes stored within a given rack will all be the same diameter and wall thickness but there are multiple pipe sizes that will be stored in different racks. I'm wondering if anybody knows of a resource that solves this general case. Default method may be to calculate the "density" of the stacked pipes and treat them as a fluid which would create a triangular force distribution on the wall but that may be too conservative. Any input is appreciated.






RE: Lateral Force From Stacked Pipes
If the stacks are stacked in such a way that the side vertical walls are resisting them then i would look at it as a vector analysis. Draw a free body diagram of three pipes stacked in a pyramid. and look at how the weight of the top pipe flows through the bottom two to be resisted laterally. This is your thrust. Now increase the weight of the top pipe to match a height of total stack (ie 20 pipes) and see what that thrust is. When you expand the model to 3-levels of pipes it should make complete sense and you can tell how it works with N-levels without any more models. These models can just be mental exercises. There is no friction.
I would not assume that the pipes sit directly on top of each other, not in perfect vertical/horiz rows, but rater each row will be offset 1/2-Diameter. They will stack in a dynamically stable position.
And you may also want to check if blocking is added between rows, I have seen it with 4x4s between every row to increase ease of lifting with forks.
RE: Lateral Force From Stacked Pipes
I'm totally guessing here, but I'd guess the force is opposite of fluid pressure. The lateral loading the top pipe places against the side wall is much higher that the load placed at the bottom. The force at the bottom is very small. I would start by looking at what pipes would fall if you release the side but held the bottom pipe in place. Some sort of triangular shape. I'd directly apply the vertical weight as a horizontal load to the side wall. Than I'd multiply by 3. Or 6. Maybe 10.
There is no extra credit for saving material costs. Assume the operator is lazy and throws pipe against the sidewall. Just thinking out loud-I have no experience with this. I would want to play around with this till I was comfortable.
_________________________
Tony Krempin, PE
TopKnot Engineering
RE: Lateral Force From Stacked Pipes
Mike McCann
MMC Engineering
RE: Lateral Force From Stacked Pipes
RE: Lateral Force From Stacked Pipes
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Lateral Force From Stacked Pipes
The size of pipes being stored ranges from 3" diameter to 12". Each rack will contain pipes of the same size at a given time.
RE: Lateral Force From Stacked Pipes
RE: Lateral Force From Stacked Pipes
RE: Lateral Force From Stacked Pipes
RE: Lateral Force From Stacked Pipes
P=density x 1 - sine of friction angle / 1 + sine of friction angle. For equal spheres that friction angle is near 26 degrees.
Therefore, an equivalence fluid unit weight (P) would be 0.39 times what ever unit density you decide you have. This is a triangular pressure distribution. For impact, the lateral load imposed would be 0.39 times the effective vertical load from the drop. I'd just add that as a horizontal load at the top of the vertical brace.
RE: Lateral Force From Stacked Pipes
RE: Lateral Force From Stacked Pipes
Offhand, I would say it is not a good idea to stack pipe in this way.
BA
RE: Lateral Force From Stacked Pipes
What is a better way to stack pipes? Not only pipes but steel rods, logs, Newspaper rolls, Steel sheet rolls, etc, get this treatment. Very common. One way to answer his question for sure would be to do a trial model with light load measuring scales. The width of the "U" also affects the result. A test easily done at his shop. However, my method has been tested plenty. It needs a few "( )"'s
P= pipe density x (1 - sine of friction angle) / (1 + sine of friction angle). Where P is the density of an equivalent fluid. The higher the stack, the higher the loading.
This formula is for infinite width of stack. Worst case. It assumes a horizontal top of pile. Going higher, without spilling, adds to this "equivalent" density. It can add 12 percent to total loading, for a 26 degree friction angle.
RE: Lateral Force From Stacked Pipes
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RE: Lateral Force From Stacked Pipes
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