Moment Arm & Metal Banding Material

[ReverseEntropy]

It's been awhile, so can someone confirm my thinking? It is common to strap auxillary items (like an antenna mount) to a pole. As such, the moment arm would be the sum of (a) the distance the mount is offset from the pole + (b) the pole diameter? ...or pole radius?

My instict says to use the pole diameter. Is that correct?
Thanks in advance!

 

[EngineerTex]

Is the pole round? If I understand your question, then it is the offset plus the radius.

That is the specific case.

The general case is that you calculate the moment transferred into a member by:

M=F*d

Where:

M=Moment
F=Force
d=distance from line of action of force to the c.g. of the section.

If your force isn't acting perfectly parallel to the axis of your beam, you split up the forces into their components where the parallel component contributes to bending and axial loading while the perpendicular component contributes to shear.

-T

Engineering is not the science behind building. It is the science behind not building.

 

[ReverseEntropy]

MechTools, thanks for the reply. I recognize that is rather basic, so I had to rethink what is puzzling me. So, let me re-phrase the question: Is the following correct?

For something banded to a pole, there will be a reaction force equal and opposite to the load it is supporting. So, when summing the moments, this reaction force acting upward at the banding will create a moment with a moment arm equal to the radius of the pole (assuming the banding is flush against the pole).

It's been awhile, but when running through such academic exercises on eccentric loading, my notes (and text examples) show no discussion of reaction forces. Typically, these problems have the eccentric load's supporting member (i.e., a board) nailed to the center of a post thereby aligning the reaction force with the z-axis. Perhaps, this oversimplified the problem.

Your feedback on this is appreciated.