I beam vs tube

[scottsowers]

Witch can carry the largest load an I beam or a tube of the same steel,size, and thickness?

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[GRoberts]

In general, if loaded as a beam, the one with the largest section modulus (or moment of inertia) will be the strongest. If a tube has the same wall thickness and width as a beam flange, it will have a higher section modulus, but it will weigh more since it essentially has two webs. However, beams and tubes are never the same wall thickness or width. Beams generally have thicker flanges and thinner webs, so pound for pound, beams generally make better beams than tubes do. If loaded as a column, the one with the largest cross section will be the strongest as long as you don't get into buckling. If you are loading in torsion, generally the tube will be stronger.

 

[desertfox]

HI scottsowers

I beams are specifically designed to take vertical bending loads using the most econominal shape, they are not reccomended for torsional loads and are weaker also in the horizontal plane. As stated in the previous post the section with the greatest "2nd moment of area" sometimes mistakenly called (moment of inertia)in lots of text books
will have the greatest resistance to bending.
Circular tube however will have the same resistance to bending in all planes and is reccomended fot torsional loadings as well. Square tubing will also have equal bending resistance in both the x-y planes and again can be used for torsional loading.If you can post the sizes and application for the tube and I beam that your thinking of we can help you further.


regards desertfox

 

[civeng]

Hi Scott,
One important point in choosing your beam is also the cost of connections. The cost for connections for tubes is alot more than for I beams. Also the cost of the tubes are alot higher than I beams (especially these days!)
Hope this helps your choice.
Have a good one.

 

[3dboy]

Hss sections have much longer "unbraced" lengths than I-beams do, however, if bracing is not an issue, (say with a continuously fastened metal deck) then pound for pound the I-beam is the way to go.

 

[Michael996]

You have stability issues to address, too. Where and how the load is applied. Tubing as a slight advantage is you are applying the load off center of the beam.

 

[desertfox]

http://www.engineersedge.com/beam_bending/beam_bending2.htm

regards desertfox

 

[scottsowers]

desertfox

Thats what I was looking for!
Thanks