Hi, I hope there's someone knowledgeable about load-bearing capacities here.....
I've been struck by the flat roof problem on the garage, meaning flat roof and Sweden = disaster....
I now have to tear down the existing roof and lay a new one, and naturally, I was thinking of changing it to a pitched roof but to complicate things a bit, I want a cathedral ceiling to get a proper interior ceiling height.
Now that I've been calculating this and also checked Moelven's website, I've come to the conclusion that it must (in wood) be a beam of 115x630mm that is supported at each end down to the concrete floor. However, I think the beam becomes both large and expensive, and therefore I'm considering whether it can be replaced with a steel beam to reduce both dimension and cost.
Specifications.
Snow zone 2 gives a load = 50kN/sqm
Length = 8.9 m (beam length)
Width = 7.2 m
Height outside will be 4.5 m
I therefore need information about the dimension of the load-bearing steel beam and the supports (2 pieces).
Please help me with this........
Anders
I've been struck by the flat roof problem on the garage, meaning flat roof and Sweden = disaster....
I now have to tear down the existing roof and lay a new one, and naturally, I was thinking of changing it to a pitched roof but to complicate things a bit, I want a cathedral ceiling to get a proper interior ceiling height.
Now that I've been calculating this and also checked Moelven's website, I've come to the conclusion that it must (in wood) be a beam of 115x630mm that is supported at each end down to the concrete floor. However, I think the beam becomes both large and expensive, and therefore I'm considering whether it can be replaced with a steel beam to reduce both dimension and cost.
Specifications.
Snow zone 2 gives a load = 50kN/sqm
Length = 8.9 m (beam length)
Width = 7.2 m
Height outside will be 4.5 m
I therefore need information about the dimension of the load-bearing steel beam and the supports (2 pieces).
Please help me with this........
Anders
Snow load of 50 kN/m2 seems a bit much??
Did you write that correctly?
My memory says that Snow Zone 2 provides a load of 2 kN/m2. Then the dead weight of the roof itself is added....
How did you come up with the 50 kN/m2??
Did you write that correctly?
My memory says that Snow Zone 2 provides a load of 2 kN/m2. Then the dead weight of the roof itself is added....
How did you come up with the 50 kN/m2??
Map strength goes it with
(haven’t calculated deflection!)
IPE 300 weighing 42kg/m
or
HE240A weighing 60kg/m
The weight reflects the price!
These will be heavy beams.
Isn't it smarter with traditional trusses?
Probably significantly cheaper.
(haven’t calculated deflection!)
IPE 300 weighing 42kg/m
or
HE240A weighing 60kg/m
The weight reflects the price!
These will be heavy beams.
Isn't it smarter with traditional trusses?
Probably significantly cheaper.
anaitis:
Out of sheer curiosity, I'm wondering how you've calculated it.
Deflection and strength of the beams I'm familiar with, but how have you calculated the load?
Snow zone 2 = 2kN/m²?
Self-weight = 0.5kN/m²?
How much of the roof do you assume loads the beam, should logically be half the area, right?
The roof angle should also matter when it comes to how many m² the roof is?
As you can see, I would appreciate some explanations in your calculation.
Out of sheer curiosity, I'm wondering how you've calculated it.
Deflection and strength of the beams I'm familiar with, but how have you calculated the load?
Snow zone 2 = 2kN/m²?
Self-weight = 0.5kN/m²?
How much of the roof do you assume loads the beam, should logically be half the area, right?
The roof angle should also matter when it comes to how many m² the roof is?
As you can see, I would appreciate some explanations in your calculation.
The beam takes the load from half the width of the roof.Gabbe1 said:
This gives me the line load q= 2.5 * 3.6 = 9 kN/m. I completely disregard the roof angle, it's only about 30 degrees (I don't really know the geometry of the house).
Considering the angle would give a slightly lower load since more load would go directly to the walls, but at the same time, the beam might be slightly heavier. It probably evens out. Otherwise, the snow load is calculated on the horizontal surface, so that checks out.
I did the calculation on a small notepad when I had a moment during lunch.
You can't expect great precision in 5-6 minutes!
But the calculation is on the safe side!
Ok, then I understand.
But if I now calculate in this simplified way, I get the distributed load Q to be 80100N (3.6x2.5x8.9).
The maximum moment in a simply supported beam subjected to a uniformly distributed load is: Mmax = -QL/8
A standard beam today generally has a yield strength of 355Nmm2.
I then get that the desired section modulus W becomes 251cm3.
This means that an IPE220 or an HE 180A can do the job if one can live with the deflection and disregard safety margins.
However, it's not wrong to include a safety factor, and in that case, the beams that anaitis mentioned earlier are more suitable.
But if I now calculate in this simplified way, I get the distributed load Q to be 80100N (3.6x2.5x8.9).
The maximum moment in a simply supported beam subjected to a uniformly distributed load is: Mmax = -QL/8
A standard beam today generally has a yield strength of 355Nmm2.
I then get that the desired section modulus W becomes 251cm3.
This means that an IPE220 or an HE 180A can do the job if one can live with the deflection and disregard safety margins.
However, it's not wrong to include a safety factor, and in that case, the beams that anaitis mentioned earlier are more suitable.
You should not design directly to the yield strength!Gabbe1 said:
For instance, steel 1411 and 1412 have a design value of (at worst) 205 MPa,
and steel 1311 and 1312 have 182 MPa.
Now I don't remember, but I think I used 180 MPa for the calculation.
It seems like you are an engineer?
Calculations in construction generally use the same formulas,
but in construction, there are a number of laws and regulations one must follow!
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