Calculation help (a very unusual project, 8-sided woodshed with 1 foundation post)

[Ejansson]

Hello everyone,

I am working on an unusual construction project (or rather preparing for it by casting a foundation).

I am going to build an octagonal woodshed (model gazebo), so far nothing strange.

But I will only have a foundation in the middle Ø700mm and then a concrete lid cast on top of this. Ø1600mm, but I would now like to know what the largest diameter is that I can place 2"8 on this (like a star) and then have posts at the outer end.

I work in construction, so I have drawn it all up in CAD and concluded that with a Ø3500 diameter on the woodshed, I can manage with a steel beam that is 120x40x2, BUT I would like a total of 4m, meaning 1.2m without support and replace the steel with 2"8 or alternatively 2"9.

Regarding the attachment in the middle, there is no problem, I have solved that; the question is whether it works with 1.2m in overhang.

I live in snow zone 2.5.

I will attach some images from the 3D CAD as soon as I find the file; feel free to suggest ideas.

Thanks in advance.

 

[PerOF]

Hello Ejansson! Sounds like a spinning windmill. The hardest part is probably the sideways stability. The old windmills had long stays at ground level. Now, of course, a woodshed is much less wind-catching. But it can become unevenly loaded as you fill it up and take out wood. Best regards, PerOF

 

[Ejansson]

Hi PerOF.
Thanks for the tip, however, the wind resistance on this is not particularly large, so I don't see side-to-side stability as a problem at all, actually, the question is just whether I can build without a central post..

 

[Ejansson]

So last night I pulled myself together and sat down to fix the calculation.
90cm overhang resulted (at 2"8) if anyone is interested, calculated conservatively with a safety factor of 1.15, did an FEM calculation on it, so now it's just a matter of seeing if it will be carpentry this year or next year...