max allowable center point load on 14' span

[TinnerDave]

I am trying to support 200lbs on a 14' span. i am a project manager for a mechanical contractor and am not privy to all the math involved. i would prefer to use angle, but am not opposed to channel if it's necessary. My gut tells me 4x4x1/4 is safe, maybe 3x3x1/4. i would like to use beam clamps on the edge of the horizontal leg, but can drill closer to the vertical leg if i gain some capacity by reducing torsion. any help is much appreciated. thank you in advance.

 

[SwinnyGG]

Surely you have an engineer in the building. You need to engage them.

 

[TinnerDave]

I do not have an in house engineer.

 

[SwinnyGG]

My suggestion would be to hire one.

Designing stuff like this is performing engineering. You (or your employer) are open to a lot of liability by doing even simple tasks like this without a qualified person on staff.

I would venture to guess that no one here is going to calculate something like this for you- because we would not be willing to absorb an unknown level of liability should whatever you're building fail and kill somebody.

 

[Tmoose]

This post probably belongs somewhere other than in the "bearing" forum. Maybe structural.

What is the nature of this 200 lb load?
Permanent static?
One time lift?
Man lift?

To prevent the channel rolling from torsion, the load needs to be applied at the "shear center".
Counter to my intuition as a young man, that point is outboard of the channel, like this -

https://www.quora.com/What-are-methods-to-calculate-shear-center.

 

[TinnerDave]

Thanks for the input Tmoose. It is permanent. It is air conditioning duct, so it isn't officially static, but the seismic forces of low velocity duct are pretty minimal.