Platform Structure material thickness

[mnray]

I'm building a 6'x12' steel platform that will be 3' elevated from the ground. How can I determine what load bearing weight will be if I use 2" Square Tubing, 1/4" wall thickness and then use 1/4" angle iron for the platform structure? I was going to use 2" Sq tube, 3/8" thick, but most local suppliers in my area only stock 1/4" thickness. There will be approx. 500 lbs of equipment on the platform (stationary) and from time to time 3 adult workers, so I figure approx 1,500 total weight (maximum).
I need to know if 1/4" supports will hold this platform up. Thanks for your help and direction. I have an attachment that shows the basic platform that I will be welding.

 

[Travis_King]

Depending on where you are located, any drawings that are used for the construction/fabrication of platforms which will be occupied by people, or equipment which will be operating near where people work, needs to be stamped by a professional engineer. Please check into your local and federal codes.

That disclaimer at the top means that you can't just use their design because they sell it. You have to stamp your own drawing after having your own PE look at it.

 

[mnray]

Yes, thank you Travis, this is just an example of what will be built. I probably should have used a photo of a platform for general discussion. For example this drawing shows 5" x 3/8" angle as the legs. I'm inquiring about 2" Square tubing 1/8 thick. I had read other post where people suggested adding a photo or drawing (to clarify) what was being asked. When using the general word "platform" you can get discussion on everything from catwalks, to beds... I was just trying to get a formula or any idea if what the load strength of 2" Sq, 1/8" thick material would be. Thanks again.

 

[Travis_King]

Yep, it's always good to include pictures. I was just making sure you knew that if people are going to be on it, you need to have it stamped. Which means you'll need a professional engineer to be a part of the design process, review the calcs, and stamp it. We can't recommend anything else here, as (assuming you're in the US or Canada - and not in an underground mine) doing anything else would be illegal and would open you up to loads of liability.

The load strength of 2" square stock alone is pretty well defined, but it depends on how the bar is loaded. This is based on the yield strength of the steel (multiplied by a safety factor, a lot of times this is like 0.6*yield; standards vary). Look up your applicable building code, they'll tell you what to use. It also depends on the area moment of inertia or section modulus, which you can find easily online, and you'll want to know the modulus of elasticity (young's modulus) for the type of steel you're using; also found online.

The bigger issue for you is that these won't be loaded just axially, they are part of a structure. You'll have to look up some steel design if you'll be doing the preliminary sizing. There's no one formula for the strength of a member in a structure. It depends on the structure and where and how the expected loads are applied.

 

[nvn]

mnray: In a quick check, the minimum bending strength of 127 x 127 x 9.525 mm structural angle appears to be 2.19 times greater than 50.8 x 6.35 mm square tube. And the minimum bending stiffness of 127 x 127 x 9.525 mm structural angle appears to be 3.87 times greater than 50.8 x 6.35 mm square tube. Therefore, 50.8 x 6.35 mm square tube currently appears to be weaker than 127 x 127 x 9.525 mm structural angle.