# Bending Moment Maximum Force

1. Apr 22, 2010

### Tolale

Hi
For a project im doing i need to know the maximum load an "I" Beam made out of balsa wood can take. Looking through the internet I found the "Euler Buckling Formula"

F = $$\frac{E I pi^2}{l^2}$$

When I use this formula I get a load which is too big, and I think this mght not be the formula or im doing something wrong.

I = 87499.99 mm^4
L = 400 mm

I find loads of different values of E for Balsa wood, so Im not sure if thats what im doing wrong.

Thanks

2. Apr 22, 2010

### Studiot

How do you know this load is too big?

Euler's formula has little to do with a beam in bending. So if you are really talking about the bending of beams you need to talk to your teacher.

You should not just pull formula out of a book or website.

3. Apr 23, 2010

### Tolale

Ok, if it's not that equation, then which is it.
THe beam is a boom in a crane made out of balsa wood, it's hinged on one side and the other side will support the load.
What I'd want to find out is the maximum load the boom would withstand in bending like that, I thought it was the Euler equation, But using Young's modulus I found for balsa wood, it gives me a ridiculous answer.
Id appreciate any kind of help, thank you

4. Apr 23, 2010

### Andy Resnick

IIRC, your equation is relevant for buckling loads- that is, the load is axial along the beam. That's different than loading a cantilevered beam, where the load is perpendicular to the beam axis.

The detailed formulas depend on the geometry of the beam, the way the beam is held in place, and the distribution of the load, but for most applications, you should be able to find a better formula here:

http://structsource.com/analysis/types/beam.htm [Broken]

Roark's book has a bizillion different cases worked out. The maximum load to failure is described in terms of the yield stress of the material (which is different than Young's modulus), but some useful information is in the bottom half of this page:

http://www.engineersedge.com/strength_of_materials.htm

Does this help?

Last edited by a moderator: May 4, 2017