Design and fabrication chat
- Thread starter mrblaine
- Start date
1, not as slender
2, I wasn't very clear. I don't expect the example stairs to fail as there's a lot of steel there. I'd be surprised if it doesn't hold up just fine. But for how much steel there is, it's relatively weak, and I would expect to see buckling if it did fail.
I didn't post that picture in response to you. I put it up for comparison to the subject steps. Plus if these are used for working on things I'd want them mobile and the subject steps are forklift heavy.
I agree the verticals especially on the upper portion are one of the things I don't like about it as they aren't braced from buckling and even if they were they are unnecessary.
OP
No, my premise was that the angle braces are what you do when you don't fully understand the design. The butted tubes welded on just the first step alone negates the need for the angle braces, much less the subsequent repeats of the same feature. I explained that the butted tubes each act like a gusset and that was confusing somehow, so I built a working example to show what I was describing and a test to show how strong it really is.
OP
I believe it and if you did want to add a brace to do anything more than what is there, some 1/8" x 1" flat bar done like I've drawn would get the rest of it with little effort and added weight.
If someone were to ask how I would build these I would build three matching panels. The boards would act as the spreaders for the the top and couple flat bar Xs take care of any racking. That way it could be shipped flat and easily assembled with a handful of fasteners.
While I understand the why a far larger span is worse, is the top step not doing the exact same thing as your post on the last page hence rendering cross supports less necessary? We could run simulation based on load but I’d guess it’s unnecessary.
OP
Reread. Maybe had one too many tonight. You would be correct in your assessment - at least prior to this comment.
At risk of doubling down on my last error,
I was trying to come up with a case as to how this load scenario isn’t the same as what the step/platform is. Best I can think this is actually worse (not in magnitude, that is obvious, but rather direction).
With this I know you weren’t suggesting eliminating every iteration of this on the step/platform, but let’s say we only did the first iteration and eliminated the rest, would we be worried about buckling (which seems to be the most common concern) or another mode of failure?
Very late into this thread. That platform is a hot mess. It looks like the person who was responsible for the design doesn't regularly work with steel, and likely does things with wood. I say that because those type of people have 2x4s and 4x4s in their head size-wise, and they fail to consider how much stronger and stiffer steel actually is. As a result, they add more steel until, in their head, it looks like the volume used is slightly less than the volume used for a wooden structure.
Steel weldments (assuming competent welding) are significantly stronger and stiffer than wood structures nailed or screwed together, especially at the joints. Unlike wood, the welded corners have strong resistance to moment loads (torques). That's why corner braces on that platform are equivalent to suspenders in a belt and suspenders world.
Regarding buckling, I just calculated the critical Euler load for a 48 inch column made from 1" square tubing with 16 gauge walls. It would take about 2,400 pounds to buckle it. Buckling isn't a concern I would have.
If I was designing that platform solely for my use (where no one else could get hurt by a poor design), I'd use 1" x .062 tubing with minimal bracing and try it. If I was concerned about weakness after the basic frame was done, I'd add bracing as required. However, if I was designing this as an engineer for others to use, I'd do a few more structural calculations to be able to defend my design.
Steel weldments (assuming competent welding) are significantly stronger and stiffer than wood structures nailed or screwed together, especially at the joints. Unlike wood, the welded corners have strong resistance to moment loads (torques). That's why corner braces on that platform are equivalent to suspenders in a belt and suspenders world.
Regarding buckling, I just calculated the critical Euler load for a 48 inch column made from 1" square tubing with 16 gauge walls. It would take about 2,400 pounds to buckle it. Buckling isn't a concern I would have.
If I was designing that platform solely for my use (where no one else could get hurt by a poor design), I'd use 1" x .062 tubing with minimal bracing and try it. If I was concerned about weakness after the basic frame was done, I'd add bracing as required. However, if I was designing this as an engineer for others to use, I'd do a few more structural calculations to be able to defend my design.
I would have made the base frame and the frame for each step and the platform and only used vertical supports on the corners of each. Once the wood is in its frame it shouldn’t flex under weight at those lengths.
OP
A neighbor once asked me to build him a stand for his 100 gallon fish tank. I asked a few questions.
How tall? 36"
Anchored or tied back to a wall for our earthquake crap now and then? Tied back.
Glass or Acrylic? Acrylic
Rough size of the footprint? Show style, about 18" front to back and 48" long.
When I got all of them and figured out the load was about 800 lbs. max, I told him with a shelf to support the equipment and all welded up, the most he would need is 1" square tube in a way overkill wall thickness of .120. The .120 was just to make it easier to weld, nothing more. For aesthetics, we'd use 1" x 2" cross bars to build the frame for the wood top.
He called me a stupid idiot and said the smallest it could possibly use was 2" x .250 wall square tube. I just smiled and asked if he was making a work bench to hold up one end of the space shuttle and politely said it was best if he asked someone else.
Gunnersmate
TJ Enthusiast
OSHA Violations. Hand Rail
OSHA Violation. tread and riser should be 7 and 11
Treated Lumber for the steps
2x12 for the steps
Non Skid for the steps
7 inches from the top of one step to the top of the next step (7 and 11)
And About 1/3 to 1/2 less for as much metal used in construction
some wheels if you plan on moving it
Steps fastened to frame
Also you could have skipped that 2x12s and used 5/4 deck boards and saved a little coin and weight
OSHA Violation. tread and riser should be 7 and 11
Treated Lumber for the steps
2x12 for the steps
Non Skid for the steps
7 inches from the top of one step to the top of the next step (7 and 11)
And About 1/3 to 1/2 less for as much metal used in construction
some wheels if you plan on moving it
Steps fastened to frame
Also you could have skipped that 2x12s and used 5/4 deck boards and saved a little coin and weight
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Yep, I use CREW 1" x .062 tubing for many things because it's cheap, light, strong, and with no mill scale, it's easy to paint.
At my day job I get asked a lot about materials like what is used for driveline construction, what should be used for things like control arms for buggies or what should be used for building ATV trailers. Led to getting into a conversation with an oilfield welder a week ago that told me there is no reason I could not just use some pipe for a driveshaft. He became quite offended when I told him the pipe was for poop. It still boggles my mind when the phrase "I have been a welder for ..." comes out and yet they do not know that pipe is a vessel and tubing is a structural member.
I've got some extra tubing laying around and have been pondering what to build with it