Understanding Steel Tubing Strength: Calculating Buckling and Maximum Load

[feiner]

I was wondering if anyone knows where I could find charts with the weights that steel tubing, both square and round, buckles at or provide me with equations to calculate it myself as well as the amount of downward force that can be applied to a vertical piece of tubing before it bends. I'm sure my wording is horrible so if you don't understand just let me know and I'll try to explain better.

 

[FredGarvin]

So, basically, you want a quick rundown on an entire course of mechanics of materials? Honestly, you need to do a little more leg work of your own. It is very difficult to answer general questions like these. If you do some research into the theory and have specific questions, it is much easier to help.

Buckling depends on the end conditions of the column in question as well as the cross section geometry. The compressive force allowable is a function of the material. Any book on mechanics will have those allowables.

 

[structural_guy]

Hmmmmmmm...

I was wondering if anyone knows where I could find charts with the weights that steel tubing, both square and round, buckles at or provide me with equations to calculate it myself as well as the amount of downward force that can be applied to a vertical piece of tubing before it bends. I'm sure my wording is horrible so if you don't understand just let me know and I'll try to explain better.

The official guide to the subject (assuming the most commonly used material: steel) would the AISC Steel Construction Manual. In it you will find the current code adopted specifications for designing structural tubes or steel pipe sections under axial load, lateral load, or a combination of the two. The tricky thing in what you're asking is the effect of Euler buckling based on your incidental eccentricity, meaning the inability to perfectly balance load applied to an axial member. Your end conditions are vital in determining the "K" factor, which basically is a function of the deflected shape. The height or length of your section will also greatly influence its allowable loads before buckling. The shorter and stouter the column, the more load it can take. Length as compared to section slenderness (called the slenderness ratio) directly influences a sections likelihood of buckling. Other materials use slightly different codes. All design codes give a stress limit that has a built in safety factor and empirical (determined experimentally rather than derived from first principals) constants embedded in the formulation. There is no true cure-all formulation for buckling phenomenon and it is an area still being researched.