Depends on how the tube is loaded.  Like a post or like a floor joist?

Brian

You need to provide much more information, or find a copy of this.  

Quoted: Depends on how the tube is loaded.  Like a post or like a floor joist? Brian

+1. There's a big difference in how the load is taken by the tube. Axially? Laterally?

Try here if you have the data.

Quoted: Where would I find the colapse rating on mild steel square tubing.

It says right in the description.....

Sex Swing Stand Sex Swing Stand Free standing steel sex swing stand supports up to 400 lbs and works with any single support swing. The wide support stance provides total stability and freedom of movement with built in steel loops for added restraints.  Assembles in less than 10 minutes, weighs 40 lbs and can be easily stored or transported when not in use.

Dolly will be ok.

Structural steel is not load/span rated like lumber. There is a mathematical equation used to find "moment of inertia". Needless to say you don't want to find moment of inertia through trial and error.

Box tubing is fairly rigid stuff even in light gauge. Box tubing also is avaiable in rectangular configuration for reduced deflection.

What are you building and how long are the spans, how much load?

Quoted: Quoted: Where would I find the colapse rating on mild steel square tubing. It says right in the description..... Sex Swing Stand Sex Swing Stand Free standing steel sex swing stand supports up to 400 lbs and works with any single support swing. The wide support stance provides total stability and freedom of movement with built in steel loops for added restraints.  Assembles in less than 10 minutes, weighs 40 lbs and can be easily stored or transported when not in use. nawtythings.com/a_graphics/furniture/f13.jpg Dolly will be ok.

Wont it need to be upgraded and reinforced for use with a horse?

Quoted: Sorry, I posted that in a hurry and was not able to get back. I am dealing with 2"x6"x.125 and 2"x6"x.188.  Rec. tubing.  It lays on edge with the 6" being vertical.  I am trying to find the distortion and or colsapse #'s. Will look at the link. thanks.

What's the span? These tubes will have a pretty good bending capacity, but not much shear capacity because the walls are so thin.

I will run a couple numbers and get back with you shortly. In the meantime, if you can tell us the span, we can estimate the load rating.

The 2.0x6.0x0.188" tube has a shear capacity of about 5,400 lbs, and a moment capacity of about 85,000 ft-lbs. With the maximum load of 5,400 lbs in the center of the span, the maximum span is 15.7'.

The 2.0x6.0x0.125" tube has a shear capacity of about 3,600 lbs, and a moment capacity of about 59,000 ft-lbs. With the maximum load of 3,600 lbs in the center of the span, the maximum span is 16.4'.

These figures are the maximum condition, and do not account for buckling of the beams, bi-axial bending, bending-axial interaction or other effects.

Quoted: Sorry, I posted that in a hurry and was not able to get back. I am dealing with 2"x6"x.125 and 2"x6"x.188.  Rec. tubing.  It lays on edge with the 6" being vertical.  I am trying to find the distortion and or colsapse #'s. Will look at the link. thanks.

It's a start. You have to define the supports and load too. What kind of supports, how many, and how far away are they? What kind of load, and where is it? Will the load be static, just hanging there, or will it be swinging and moving around? Are there any impacts involved? Will the supports be moving around?

Quoted: Quoted: Where would I find the colapse rating on mild steel square tubing. It says right in the description..... Sex Swing Stand Sex Swing Stand Free standing steel sex swing stand supports up to 400 lbs and works with any single support swing. The wide support stance provides total stability and freedom of movement with built in steel loops for added restraints.  Assembles in less than 10 minutes, weighs 40 lbs and can be easily stored or transported when not in use. nawtythings.com/a_graphics/furniture/f13.jpg Dolly will be ok.

WTF Cav?

Quoted: No span.  Sits flush on ground.

In that case, just use the maximum shear capacities I estimated above, 5,400 lb for the .188 wall and 3,600 lb for the .125 wall.

Further description of the nature of this structure would be most useful.

Fill them with concrete and cap the ends if you're worried about it...

You're just worried about them squashing ? Correct ?

You want to run wires across a parking lot  or driveway ? There are better solutions to that...
I've seen special mats with provisions for wires, tubing, etc...
I think it was McMaster Carr or Grainger....

Will edit later after work.

Quoted: Well picture it sitting on the ground with ramps on both sides and a semi truck driving over it.  So if two tires were on it...How much weight would it support before it would beging to distort?

Well, we typically assume 20,000 lb/axle for a highway truck. Divide that by 4 tires/axle = 5,000/tire. The 0.188" wall tube is right there.

Dragracer_Art's got the right idea!

Quoted: Ok will not try and lighten it up...And you guys want to add concrete. sigh.

You want it to work don't you ?

Exactly what are you trying to do ? A little more detail and maybe we can steer you in a better direction...

Use DzlBenz' 5000 lbf per tire, assume a tire is 10 inches wide (WTF, I have no idea how wide the truck tire is, but it doesn't matter as you will see) -

As the tire creeps up the ramp, it will load one web of the beam before the other, so the compression stress in that web is 5000/(10*0.188) = 2.7 ksi.

If that beam is A36 or similar mild steel, and I needed an answer right now and didn't have time to  calculate the compression buckling allowable because there are terrorists that needed to be killed right now, I would drive the truck over without a second thought.  If the ramps are an inverted U-channel, the stress is siginificantly higher.  If the ramps are flat bottom boards, the area served is larger than the tire footprint and the actual stress is lower.  Since this is a beam on an elastic foundation, unless there is something unusual in the configuration, that will also reduce the effective stress even further.  If I had a manual handy, I would calculate the buckling stress, but I don't, so I ain't.  Even with a factor of safety of 5, the stress is just over 13 ksi.  Unless these tubes are manufactured from peanut butter, they will easily support 5000 pounds at a tire.

You are more likely to have a stability problem with the tubes rolling over due to a lack of lateral restraint.

Quoted: Use DzlBenz' 5000 lbf per tire, assume a tire is 10 inches wide (WTF, I have no idea how wide the truck tire is, but it doesn't matter as you will see) - As the tire creeps up the ramp, it will load one web of the beam before the other, so the compression stress in that web is 5000/(10*0.188) = 2.7 ksi. If that beam is A36 or similar mild steel, and I needed an answer right now and didn't have time to  calculate the compression buckling allowable because there are terrorists that needed to be killed right now, I would drive the truck over without a second thought.  If the ramps are an inverted U-channel, the stress is siginificantly higher.  If the ramps are flat bottom boards, the area served is larger than the tire footprint and the actual stress is lower.  Since this is a beam on an elastic foundation, unless there is something unusual in the configuration, that will also reduce the effective stress even further.  If I had a manual handy, I would calculate the buckling stress, but I don't, so I ain't.  Even with a factor of safety of 5, the stress is just over 13 ksi.  Unless these tubes are manufactured from peanut butter, they will easily support 5000 pounds at a tire. You are more likely to have a stability problem with the tubes rolling over due to a lack of lateral restraint.

You're *probably* not at work this week, (neither am I ) which means you can do this stuff at home.

Therefore, 1GR, I'd say this is about right.

Merlin