With the right sized pipe (preferably several) and the right pre-bending, you can easily skip that self-supporting roof sheet..
But my initial thought is that you're considering using material dimensions that are far too weak for the span you have over the pool..
The question I really feel I'm missing an answer to, in order to give advice on how to proceed, is how much CAN the structure sag in the middle?
Otherwise, it's of utmost importance to know more exactly what the finished structure will weigh, because then there's no problem specifying how much you need to pre-bend the long pipes in the structure..
I have myself worked with manufacturing machines of similar lengths (but higher load) and am currently designing a machine with a similar unsupported length..
But my initial thought is that you're considering using material dimensions that are far too weak for the span you have over the pool..
The question I really feel I'm missing an answer to, in order to give advice on how to proceed, is how much CAN the structure sag in the middle?
Otherwise, it's of utmost importance to know more exactly what the finished structure will weigh, because then there's no problem specifying how much you need to pre-bend the long pipes in the structure..
I have myself worked with manufacturing machines of similar lengths (but higher load) and am currently designing a machine with a similar unsupported length..
It is certainly possible to solve with either a frame, self-supporting sheet, or a combination (as you seem to be considering). However, I agree with @Violina that you're considering dimensions that are too weak. You have a very challenging span to manage. I’ll see if I have time to calculate your suggestions later. However, I have an immediate objection regarding the sheet metal: You should absolutely not splice sheet lengths lengthwise (join two 420 cm to 840 cm length). If it is to be reasonable with sheet metal, it should be 840 cm lengths.
Absolutely. I thought you could relate deflection to the moment of inertia and give some benchmarks to start from. For example, that the proposed frame causes x mm deflection at 1000 kg distributed load, and so on. But a final dimensioning should be based on "better" figures. Didn't @Huggedugge1 mention 14 mm deflection earlier?Violina said:
The point of self-supporting sheet metal is that its profile height provides such stiffness that it supports both its own weight and the loads it is subjected to without any other supporting structure. It replaces the entire floor framework you have under the decking.Huggedugge1 said:
If it is to make any significant sense, such a sheet should run unbroken over the entire 8.4 m span. It then supports the decking on its own, and no supporting frame should be necessary.
The only dimension I see that might be reasonable is the previously mentioned TP200. It is a standard height and, as mentioned, is on the borderline in height to fit under the terrace.
Here is some data for such a sheet:
https://f.nordiskemedier.dk/2ugltroxhvfidoea.pdf
If you lay such a sheet from short side to short side and cover it with 1000 kg wood (decking and frame), I calculate the deflection with 0.7 mm sheet thickness to 19 mm. Increasing to 1.0 mm sheet reduces the deflection to 15 mm, and with the thickest sheet, 1.5 mm, it becomes 12 mm.
It is no more than 226 mm span between the beams on TP200, so only the thinnest decking is needed.
Insulation probably needs to be solved with some sprayed variant.
You might need to think through where the wheels sit on the sheet and introduce a point load.
I still think the best solution (if you don't want to make a guide that helps lift the deflected point at the end) is to focus on stiffening the load beam. Most attractive, I think, is a welded, pre-cambered profile mounted outside or replacing the existing load beam feels most attractive.
I can only agree. The idea of pre-cambered profiles is not something I've personally dealt with in practice, so it's not so prominent in my "idea bank." But for this case, where deflection is the primary issue, it sounds excellent (especially when the construction already exists).Bernieberg said:
My total height for the terrace that the deck should go under is 23.5 cm.
Then it's about how high the rail wheels are mounted. Today on the existing deck, I have 3 cm between the deck and the patio. Ideally, I would like to lower it to reduce heat loss.
I would rather skip the sheet metal, but then the weight for the existing solution increases by about 350 kg. (Joists 120*45)
Approximately 1450 kg is the total weight today.
Partly it dips in the middle of the deck. Then both long sides dip.
Partly it dips in the middle of the deck. Then both long sides dip.
I think you misunderstood me. What I understand is that it's 5 lengths of about 420 cm being joined together to cover 840 cm.E Erik Lindroos said:
I would like to jump back to the question in post #69 so we can get all issues on the table. My suggestion with a reinforced main beam will not affect how much the roof sags between the long sides.
Yes, that is correctly understood.
When I close the pool cover, it goes 3.5 cm below the pool edge and doesn't come up.
It is also a visual issue that when it is fully closed, the middle hangs down about 3.5 cm. You can see this if you place a plank on its edge between the long sides in the middle.
If you want to fix the sagging in the middle, the beam running from side to side also needs to become stiffer.
Do you have any photos or sketches of what the entire framework looks like without the decking? The more info, the better chance of coming up with good and relevant suggestions.
Will check if I find any cards.
Unfortunately, I don't have a sketch. But I found a video and some photos.