Buckling Load Problem

Barn-Unit

Hi, I am currently studying for my Masters Degree in Mechanical Engineering at the University of Strathclyde (Glasgow, Scotland) and as part of my final project I have to design a 'rig' with which to conduct experiments on climbing belays.
The problem I am having is in designing the 'rig'. I need to determine whether it would be better made from Steel or Wood but I cannot determine this without first calculating the buckling load. Here in lies the problem.

This is a quick sketch of the part of the rig I am struggling with:

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What I am trying to figure out is whether it would be better to make it thicker but out of wood, or thinner and out of steel. The forces it will be under are not going to be anywhere near the yeild levels of either material.

ALL help appreciated. Thanks!

Barn-Unit

Ok, not too sure if the picture is loading correctly...

it is basically an upright rectangular section of length around 4 times it's width, standing on it's short side (width) with a triangular 'web' on one side in the opposing direction forming a 90 degree corner. The web is as tall as the rectangular section and as long along the bottom edge (right angle triangle with 2 equal sides). Hope that helps...

Studiot

You better have another go at the drawing mate.

Why wood or steel, why not a composite?

Difficult to comment further without a proper picture, but might not the fixing characteristics into wood yield false results? The internal response of wood is quite different from rock or steel.

If I read you description correctly the support is four times as tall as it is wide, but no information about depth was given. This is unlikely to have a buckling problem at realistic depths. However it could easily be strengthened with a mid-brace.

Barn-Unit

Got the picture working, thanks for the comment.

I chose wood (ply wood) or steel because these are the materials that the lab have to hand. the fabrication time would be far too long if i were to ask them to build it out of anything else.

Studiot

By a composite I meant both wood and steel.

I do not know how many times you will need to change/adjust the belaying points. If this happens a lot, as I suspect, then wood is the easier material. However the anchor points will be 'softer' (=possess resilience) and have a tendency to twist.
I suggest making the main panel of ply, but reinforce the anchor positions with sheet steel (builder's merchant straps) to maintain rigidity. That's the best of both worlds.