# Formula to compare the strength of pipe versus C channel

1. May 31, 2010

### wroughtn_harv

What I'm trying to do is compare pipe to channel as far as lateral strength.

I have just received a patent, 7,707,794. It's for a building system of walls, fences, and buildings using steel channels and pipe posts.

The current way to build a high security fence using expanded metal panels depends upon old chain link fence brackets and framework. I believe my system provides not only a simpler and easier to build framework, it's stronger.

Here's my logic. Pipe is strong three hundred and sixty degrees. That is a good thing when building a framework for chain link fence. Chain link is a woven fabric and needs to be supported not only laterally but vertically so pipe works best.

Expanded metal on the other hand doesn't require vertical support. In fact it can provide vertical support for the framework, a sheet of expanded metal is stronger than it's parent shape as a sheet.

My system uses C channel or purlin oriented horizontally. I get the benefits of the purlin or channel's greatest strength where its needed the most for expanded metal support.

What I need is a comparison reflecting that advantage over the use of pipe in chain link fence framework. 2" X 4" fourteen gauge channel versus 1 1/4 schedule forty pipe.

I'm attaching some photos to give you an idea what I'm talking about.

I appreciate any help possible. I can make things but then I need help explaining it, darn.

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2. Jun 3, 2010

### Hologram0110

What type of strength are you talking about here? In engineering it can mean a fair number of things. Are you talking about stiffness (resistance to bending?), elastic limit (how much to bend it so that it stays bent) or yield strength (total load before it will fail)?

I'm not a civil engineer, but I believe you want to look at a beam model for whatever material the fence is made of. With a beam model you can essentially explain the force required to bend various cross-sections (Eg, why we use I beams so often). Take a look at this Wikipedia article: http://en.wikipedia.org/wiki/Eulerâ€“Bernoulli_beam_equation

3. Jun 4, 2010

### sardonicus

Harv, Interesting system. A 4" x 2" 14 ga C will be much stiffer and stronger than a 1 1/4" sch 40 pipe. For stiffness compare the moment of inertia (I in in^4), for strength compare the section modulus (S in in^3). The pipe is easy google section properties of schedule 40 pipe.

But as Hologram mentions it's hard to quantify, your expananded metal grating may pick up more wind load than a standard chain link because the air can't pass through as easily. In a way you are simultaneously comparing 4 items, the pipe, c, exp mtl, and chain link, that complicates it.

You would need to be more specific about the loading (wind load) usually you'd start with a wind speed, mph, and calculate the load in psf, and that would be different for the porosity of the screen (% open).

Hope that helps. S