Does anyone know how to calculate the amount of weight that can be supported by 1x1 14 gauge steel tubing? Or can point me to a calculator that can do that?
Need more information on the dimensions / relations of the tube and the load, for instance do you mean at the end of a cantilever beam or compression along the axis of the tube?
supported at both ends. the general idea is that this will be a platform for a bed (i think a queen size, so the sizes would be 60" and 80" long) that will be hanging from the ceiling from steel cables
Depends on how much steel tube & if there are gussets (which I would put int personally) spacing of said steel tube as well.
Here is a mockup of what I’m planning. The dimensions of the outer square are 60"x80", and the middle support bars are 18.75" apart. I wasn’t planning on doing any gussets, just welding everything together. Though I imagine that some simple gussets wouldn’t be too hard to add in.
Also, I did some math, and the total weight on the frame, supported at the four corners, will be around 500 lbs
- frame 40 lbs
- mattress and box spring 100 lbs
- person 150 lbs
- 200 lbs excess for safety
What and how will you attach to the ceiling.
Your largest bending moments will be on the long dimension, have you considered having the tubes run the length rather than cross-wise? The cross wise pieces aren’t going help much for the two long pieces.
I was planning on using eye bolts through the end pieces where they stick out from the frame and running steel cables up to other eye bolts sunk through the rafter
- https://www.homedepot.com/p/Everbilt-1-2-in-Zinc-Plated-Steel-Flat-Washers-6-Pack-802521/204276454
- https://www.homedepot.com/p/National-Hardware-1-2-in-x-4-in-Zinc-Plated-Eye-Bolt-with-Hex-Nut-2160BC-1-2X4-EYE-BLT-ZN/204588931
- https://www.homedepot.com/p/Crown-Bolt-1-8-in-x-1-ft-Steel-Plain-Wire-Rope-11916/204630455
- https://www.homedepot.com/p/Everbilt-3-32-in-x-1-8-in-Stainless-Steel-Clamp-Set-3-Piece-43074/205883048
and running them lengthwise, do you mean like this?
The question is how much deflection (sag in the middle) you are aiming for
I have never even taken an engineering class, so this could be completly wrong, but from what I can gather with the following that design would sag 7+ inches in the middle if you loaded 500 pounds in the middle of a 1"x1" 14 gauge 80 inch long beam (not crazy if a normal person sits hard on the edge)
https://www.engineeringtoolbox.com/young-modulus-d_417.html
Typical youngs modulus for steel 29,000,000 psi
https://www.engineersedge.com/calculators/section_square_case_4.htm
1" x 0.917"
Moment of inertia, 0.02441
https://skyciv.com/free-beam-calculator/
Typing the above into that beam calculator says 7.5" of deflection in the middle
If you went with 2"x4" 14 gauge tube
https://www.engineersedge.com/calculators/section_square_case_10. the Area moment of inertia would be 1.066, leading to a deflection of 0.172"
I would design for a lot more weight than just 500. Additionally you will need to put angle or something to keep the box spring & mattress on. Don’t forget people do the hibbity dibbity or hibbity jibbity . That will throw other loads into effect. Triangulation is your friend.
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the weight will not be 500 lbs in the middle. There will be a mattress on top of the box spring that will distribute the weight along the entire frame. I was trying to figure out if the cables at the ends would cause any deformation in the frame.
currently the cables and eye bolts should allow it to support around 1,200 lbs. I’m just trying to see if the frame is up to snuff. 500 was my minimum; I’m hoping for closer to 700 or 800. I’m trying to find out how to configure Inventor to show how that would work, but no luck so far. And I can’t figure out which formulas to run (if I’m even using the right ones) to analyze the tubing the old fashioned way.
And a "live load " is very different from a “static load”.
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That could certainly be a lively/dynamic load for some…
(Thanks for that Tim & Zach)
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It had to be said. Lol
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The beam calculator should look more likeFree Online Beam Calculator _ SkyCiv Cloud Structural Analysis Software.pdf (251.4 KB)
The bed frame is going to apply a distributed load, not a point load. It is a function of the section and the bending moment to calculate the strain, and a function of the section area and the load to calculate the strain. You might want to ad an angle iron section on top of it to hold the bed frame in place. I would use relatively small angle section and assume that it provides no structural value and calculate only the box section member. You probably want a safety factor in the range of 5 for something people are going to sleep 
on. If it is suspended I would want eye bolts rated for the load in shear rather than inline.
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Why in shear rather than inline (and is there a place that lists that or will i have to break out my materials textbook)? Even the most enthusiastic “sleeping” won’t move the be more than about 10°-15° (suspended about 8 ft from the ceiling makes that about a foot to a foot and a half lateral movement)
Because it is easier to overbuild than to do figure out what dynamic loading to plan for?
Just do a safety factor of 5 for the inline load. Should be plenty.
I’m curious. You are talking about Deflection and Safety Factors.
You can have unacceptable deflections and still be within a safety factors. Unless the material exceeds the modulus of elasticity (not sure correct term) and the material suffers deformation and takes a “set” it will return to its original state when the load is removed. If you’ve ever flown on a 747 or 777 it’s amazing to see the wings tips move through a range of almost 20 feet but come back to original position.
I would think you should design the structure to the maximum amount of deflection you’re willing to accept. Say 3" for example in the center. Put your static and Tim’s “Hibbity” dynamic load factors in, then keep adjusting material strength until you reach that number.
You will be well within safety factors because you are designing to just a certain amount of deflection, not maximum allowable deflection before deformation yield point.
To save weight and add strength consider adding trusses to inner frames that can’t be seen.
Given that a set of boxsprings is being included in the design I’d argue that there would be roughly zero deflection.
I suspect you could mount the box springs in a brick on each corner of the boxsprings and that the wood in that component would support the remaining weight.
Having a corner strong enough to support the cabling is likely the limiting factor.