pic: Beam Bending Example

[Alan Anderson]

Originally Posted by kramarczyk

Are we getting anything out of this? (i.e. Keep going?)

All I'm getting from this exercise is disoriented.

Don Rotolo's post talked about the stresses being greatest on the top and bottom, which doesn't match how I read the picture it's referring to. The recent images use the words "wide" and "tall", but the pictures associated with those words seem to be swapped. Help?

[kramarczyk]

Originally Posted by Alan Anderson

All I'm getting from this exercise is disoriented.

Don Rotolo's post talked about the stresses being greatest on the top and bottom, which doesn't match how I read the picture it's referring to. The recent images use the words "wide" and "tall", but the pictures associated with those words seem to be swapped. Help?

Nuts... Now that I look back I doubt that you're alone.
Thanks for saying something.

This conversation started from another thread discussing frame rails getting hit from the side which is why I modeled the beam with the load from the side and now we're mixing that convention with the typical beam loaded from top convention. I'll correct the images so that the load is on top since that seems to be the easiest to understand for anybody wandering in to this thread.

*sigh* Once again, I'm making the simple complicated.

[DonRotolo]

Um, sorry about that, I accept the responsibility for confusing the directions. When I wrote I was thinking of deflection force from above, but of course the image shows (showed?) the force from the side.

Just think in 4 dimensions and it'll all make sense.

Don

[ZsHeRm]

Is this what your looking for.....

[kramarczyk]

Originally Posted by ZsHeRm

Is this what your looking for.....

That is similar to the initial picture that started this thread, but the boundary conditions are different. What did you use?

It looks like three smaller loads, 2 up and 1 down, with fixed end faces on a shorter beam.

[ZsHeRm]

i put equal weight in each place but in differing directions....like you said the two going up are equal to the one going down all forces are equal to 200 lbs.

[ZsHeRm]

I also did a different one with the exact same force and placement as you and it still worked out. ( like the one you started off with )

[kramarczyk]

So from looking at the previous images I think we can safely conclude that

1. Taking weight out of the sides of a beam is preferable to taking it out of the top and bottom (where load is applied is top).
2. A taller beam carries a load with lower stress and deflection than a wider beam, so if you need to make 'it' stronger make it taller.

New images, just for squirrel

Originally Posted by squirrel

For the sake of making the discussion even more interesting, how about making several different shapes and sizes of beam, and applying the same (relatively small) load to them and showing them all? For example, you might have rectangular tubing with the load applied to the narrow side, and to the wide side, and round and square tubing, and an I beam, and a channel.

2" x 2" aluminum channel open to bottom
1/8" wall
1000 lbf uniform load
2.674 lbm
20318 psi max stress - Gee, why is that so much higher than the others?
.243 in max deflection