Hello! It has worked out well that I have acquired a farm for some time now, and on the farm, there are various outbuildings, including a completely empty barn of about 140 sqm (certainly an old "machine hall").
The building is solid and robustly dimensioned in walls and trusses, so when it became time for a proper garage, we quickly realized that the best option must be to build inside the barn.
The garage dimensions will be about 6000x12000, ceiling height about 3400.
There will be a car lift in the middle of the garage quite far in.
Now to the point: I want to mount an H-beam in the roof in the longitudinal direction. Partly to be able to have lighter "trusses" on the roof since they only have to support their own weight, the insulation, and a bit of plaster, but above all to be able to hang a hoist on the beam instead of various "engine cranes" and other junk.
I realized quite quickly that you can't have such a beam entirely unsupported over 12 meters, so I thought of having two support beams that run across the workshop inside the roof framework that the long beam will be welded to.
The question is whether a 180mm HEB beam is sufficient for the job, considering the hoist should be able to take about 200kg.
The transverse beams would also be 180mm HEB in that case.
I might be able to get such a beam second-hand at scrap price 5 SEK/kg + VAT. Is it worth pursuing, considering I will still have to weld the beam here at home as I can’t possibly get a whole 12-meter delivered at a reasonable cost.
My ambition is of course to be completely sure that the construction will support what I intend to lift and double that amount. I've now contacted a friend of mine who created an Excel document with the right algorithms during his time at university, apparently I just need to input the size of the web and flange as well as the steel grade. I'll get back to you when I know more.
Without having calculated it and with the reservation that I may have misunderstood your solution, I think it will work if you are only going to lift 200kg.
Please attach a sketch/drawing of how you plan to construct the beams.
I interpret the post as suggesting that the beam should somehow be part of the roof structure, but I don't quite understand how.
The beam should easily handle a 200 kg hoist. If the span is at most about 4m (evenly distributed supports).
But if it is also to function as a ridge beam for the roof?? Then you need to have a structural engineer who can calculate it. If you just make some rough assumptions about snow load, the roof's own weight, etc., it could be that the beam could have to bear about 20 tons.
Even the posts that will support the beam can be at least as critical to dimension, depending on the height the beam should be at, you might need to dimension for buckling. And also the foundation under the posts may need to be constructed carefully, with the rough assumptions I made above, you could end up with about 7 tons on a post, then it won't do to just place a beam on a thin concrete slab, it will sink right through.
Now my assumption is probably a bit exaggerated, you need someone who can calculate it more accurately.
I may have been a bit unclear, but the building is supposed to be constructed inside an existing building. Therefore, there won't be roof trusses in the traditional sense.
The roof will consist of an insulated framework that only functions as a lid on the "box." In this framework, two steel structures will be built to support the longitudinal beam from above. The transverse beams will stand on legs of steel beams (probably HEB there as well) that go down to the concrete slab.
When you want to be on the safe side, you can always test-pull your finished construction under controlled conditions with a weight that is perhaps twice as heavy as you plan to lift at maximum.
Okay, if I understand correctly, the beam only needs to support the load from the lifting device and the dead weight of the roof structure? The dead weight shouldn't be more than 30 - 50 kg per sqm. Which, however, still amounts to a few tons on such a large area.
How certain can you be that this "indoor roof" won't become, for example, a storage area?
If you want to be on the safe side, you can always test your finished construction under safe conditions with a weight that is perhaps twice as heavy as you intend to lift at most.
Twice as heavy? What safety margins are used for buildings?
I thought it was 1:5 or 1:10 that applies. It should also withstand dynamic forces during the start and stop of the hoist, not just the static load.
Ok if I understand correctly, the beam only needs to support the load from the lifting equipment, and the weight of the roof structure? The weight shouldn't be more than 30 - 50 kg per sqm. Which, however, still becomes a few tons on such a large area.
How sure can you be that this "indoor roof" won't become, for example, a storage area?
Very true! This should be avoided to ensure that no accident occurs. It will, however, be quite cramped on top of the roof since the barn’s roof is quite close by.
It is very interesting with projects like these, where you build a new house inside an old one. It kind of turns all thoughts about house construction upside down.
I think I have only read about it in fiction before. I have a faint memory of some story by Aksel Sandemose (Yes, that's spelled correctly), you know, the guy with the Jante Law.
How much does the force increase during a sudden stop or, even worse, a load that, for example, tips over and "free falls" a little bit before the wire tightens again? It might be interesting to know when doing load testing.
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