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Ned Simmons Ned Simmons is offline
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Default Strength of materials question: square tube vs angle iron

On Mon, 14 Apr 2008 14:57:50 +0000 (UTC), (Edward
A. Falk) wrote:

Hi all; about to start building a trailer. The trailer plans I
bought from trailerplans.com call for 2"x3"x1/4" angle iron. I
want to use steel tube instead. Can anybody give me an idea of what
size steel tube would have the same strength? Is there somewhere
this can be looked up?


The strength of a shape (assuming the same material) is proportional
to the section modulus. Stiffness varies with moment of inertia. In
both cases pay attention to the axis the properties are referencing;
i.e., for an non-symmetrical shape, the value will vary depending on
the direction the load is applied.

Machinery's Handbook has the info you need. I'm sure the numbers for
common steel shapes are also online somewhere. Googling - "section
modulus" "moment of inertia" steel - would be a start.

This may be useful:
http://www.engineersedge.com/section...ies_menu.shtml

--
Ned Simmons