Estimation of tensil force on a ring beam

[saad73joss]

Hello everybody
My question is quite simple but I want to be sure. Thanks in advance
i have a ring beam supporting a circular equipment. The equipment is connected to the beam by bolts.
a horizontal force on the equipment vessel generates a moment.
i want to know what is the linear force distribution (of course compression and tension) on this beam due to the moment.
Many many thanks

 

[ishvaaag]

You need to also ascertain how is the ring beam support, the other is just a matter of making a model that shows the vertical loads, the outwards force P at the center of the beam under the outwards force applied at the upper flange and its P·h/2 moment, and the supports.

If your question is about finding a closed form solution for moment and outwards force at some point of a ring, there may be for your kind of support in the mechanical handbooks. A sketch would help us to find it if we try.

 

[saad73joss]

Hi
I want to know the distribution of forces on a ring beam .
I know there is a formula but I m not sure and I do not want an approximative methode.
Let s call:
M : Moment applied on the beam
D : Diameter
R : Radius ( D/2)

So what is the linear forces applied on the ring beam regardless the material .

i attached a sketch to make it clear

Many thanks

 

[rb1957]

so you're applying a moment to the ring (F*H). if the moment was carried at two points then the couple applied to the ring would be F*H/D, yes?

if the ring is very stiff (well supported to the rest of the world, egbolted down to a contrete base, big bolts, close pitched) and if the circular equipment in also stiff then the moment will be distributed around the perimeter, yes?. a reasonable assumption would be "plane sections remain plane", so that the individual foces would be proportional to the distance from the diameter they're bending about.

clear as mud ?

 

[ishvaaag]

If we don't find (I think we will, since a circular arrangement of bolts under moment and shear), for the tensile/compressive part in bolts you may proceed as rb1957 says, it is a matter of expressing all the forces in the bolts relative to the one in one bolt, say the one sustaining the highest tensile force and then setting the equilibrium with the moment.

 

[ishvaaag]

Say look p.7 of this document

http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_STR/FDOT_BC354_4_rpt.PDF

That should be enough (codes permitting) but there's much info about bolt connections with bolts in circular arrangements out there and you can search it in the internet to suit even more the case.

 

[saad73joss]

Dear ishvaag
Actually, the formula I was looking for is in page 7 of your document
So perfect
Thank you so much thanks everybody

 

[charliealphabravo]

How/where is the ring beam supported?

 

[charliealphabravo]

I don't mean to muddy the water but i don't think the solution is that easy.

Since the system is apparently indeterminate, the stresses in the ring beam are a function of the relative stiffnesses of the equipment, beam, fasteners, and support. If the formula you are using doesn't consider this then you still have only an "approximate" solution.

just sayin...

 

[saad73joss]

My question was just the distribution so just ignore the purpose
Many thanks for all

 

[TLHS]

To be pedantic, all engineering solutions are approximations in some form.

 

[JStephen]

In the tank world, the normal assumption is that the distribution is the same as beam bending, in other words, rb1957's answer above.

Everyone knows this is approximate. If you want "exact", then you're forced to account for soil stiffness, foundation stiffness, and a lot of other factors, all of which are approximate at best, so you don't necessarily gain anything but complexity.

 

[SAIL3]

as mentioned by others your analysis will be approx wheather you analize it by building a model and input assumptions on boundary conditions, stiffeness etc that are at best approx......
the problem you are dealing with has been addressed in "Pressure Vessel Design Manual" By Dennis R Moss

 

[saad73joss]

I agree with you all guys
Many many thanks