Hello everyone, I've seen that there are many skilled individuals helping with the dimensioning of beams. For glulam, there's a nice guide at https://www.byggbeskrivningar.se/dimensionering/ but for steel, I can't find anything similar. Here comes some information.
Summer cottage, 1-story, wooden house.
About 30-degree roof pitch, roof tiles (look heavy)
8 meters "wide" between the long sides, i.e., 4 meters from the ridge.
I wish to insert a window with a width of 2.5m on the long side.
The guide above suggests
Glulam 66×270 GL28cs, deformation 7 mm (L/341), utilization rate 79%
Unfortunately, the construction height of 27 cm is way too much. I wish for minimal (or less) construction height.
Summer cottage, 1-story, wooden house.
About 30-degree roof pitch, roof tiles (look heavy)
8 meters "wide" between the long sides, i.e., 4 meters from the ridge.
I wish to insert a window with a width of 2.5m on the long side.
The guide above suggests
Glulam 66×270 GL28cs, deformation 7 mm (L/341), utilization rate 79%
Unfortunately, the construction height of 27 cm is way too much. I wish for minimal (or less) construction height.
After some tinkering with the roof's own weight, I can get it to show
Limträ 115×180 GL30c, deformation 12 mm (L/210)*, utilization rate 84%
I forgot to mention that the maximum width of the beam is 130mm. I do prefer wooden beams, but the construction height must be reasonable. Maybe you can place two beams next to each other that together are <=130mm
Additionally, there is already a crossbeam, measuring 130x70. The idea is to let this remain in place, perhaps this is a misjudgment?!?
Limträ 115×180 GL30c, deformation 12 mm (L/210)*, utilization rate 84%
I forgot to mention that the maximum width of the beam is 130mm. I do prefer wooden beams, but the construction height must be reasonable. Maybe you can place two beams next to each other that together are <=130mm
Additionally, there is already a crossbeam, measuring 130x70. The idea is to let this remain in place, perhaps this is a misjudgment?!?
115x180 is significantly less stiff than 66x270. If you are going to use a 115 mm wide beam, it should be 225 mm high. The smallest steel beam you can use is an HEA 120 (114 mm high). A square tube, VKR 120x80x8, also works well. The conversion to steel is based on 66x270 glulam, and that it is correctly dimensioned.
Oh my, this information is worth gold.
the same page suggests the following side columns. these work excellently I think, even if you use steel
Limträ 90×90 GL30h
Utilization rate 25%, Support reaction 20,005 kN Minimum support length (outer) 12 mm
@justusandersson, when you mention the square tube you write VKR 120x80x8, just to be on the safe side, the height here is 80, i.e. the beam is "lying"?
the same page suggests the following side columns. these work excellently I think, even if you use steel
Limträ 90×90 GL30h
Utilization rate 25%, Support reaction 20,005 kN Minimum support length (outer) 12 mm
@justusandersson, when you mention the square tube you write VKR 120x80x8, just to be on the safe side, the height here is 80, i.e. the beam is "lying"?
richardtenggren
Ingen-gör
· Norrlandet
· 6 615 posts
richardtenggren
Ingen-gör
- Norrlandet
- 6,615 posts
No, a cross-section should be as high as possible to provide maximum load-bearing capacity, as the formula for the moment of inertia for a rectangular cross-section is I=(b*h^3)/12.
So VKRn should definitely be upright to be interchangeable with HEA120.
So VKRn should definitely be upright to be interchangeable with HEA120.
In the steel tables, it says VKR 120x80x8, which I find a bit backwards. However, rectangular tubes can be used both vertically and horizontally, but with different properties.
Perfect answers, the only thing I would have liked to have confirmed is that there are no issues using glulam as columns, like Limträ 90×90 GL30h. Wood feels convenient as I can easily screw the intended window into the "columns".
Then I feel like it's just a go-ahead
Then I feel like it's just a go-ahead
It is completely OK to use 90x90 laminated wooden posts here.
Since I received great help last time, I'm sneaking in a new question (same building as in the first post). This time it's concerning a width of 165 cm. This means that 1 load-bearing vertical stud will be removed. This time it's less tight so a wooden stud could be an option.
Unfortunately, Justus is no longer with us and it seems there isn't any other structural engineer who significantly helps with dimensioning.H Hoppehare said: