Steel beam calculation of dimension...HELP!

[JKrister]

Can't do it in my head, but the easiest way is probably to start with above 90x405 GL30c and replace it with an IPE beam. It's deflection that determines so
I*E(wood) = I*E(steel)
(b*h^3/12) *E /E(steel) = I
Then look at the IPE table and see which beam has a larger I than the calculation above.

 

[EliasAphram]

There is something wrong in your calculation that I cannot explain, but if you choose the dimensions you have calculated, at least you haven't under-dimensioned. Otherwise, I would suggest 90x360 for the beam. The columns handle the load excellently, but that is also the minimum dimension.

Yes, exactly, I haven't under-dimensioned, but I would prefer a steel beam instead, as it doesn't protrude as much. Do you know the easiest way I can convert the specified glulam beam to a steel beam?

 

[witten]

It's a bit backwards to first calculate a wooden beam and then translate it into a steel beam since the required moment of inertia is determined based on different conditions related to climate and long-term effects.

 

[justusandersson]

@wittens' observation is important. There isn't a straightforward translation in all situations between a glulam beam and a steel beam. Inserting a steel beam into an environment that only contains wood is not always successful. Various types of attachment problems can arise. It's often better to choose a glulam beam with a slightly different profile to reduce the height. Instead of 90x360, you can choose 140x315. It is always cheaper and simpler. If you insist on steel, an HEA 160 beam might be suitable, but it will be significantly more expensive.

 

[EliasAphram]

@wittens's remark is important. There isn't a straightforward translation in all situations between a glulam beam and a steel beam. Placing a steel beam in an environment that only contains wood is moreover not always successful. Different forms of fastening problems arise. It is often better to choose a glulam beam with a slightly different profile to reduce the height. Instead of 90x360, you can choose 140x315. It is always cheaper and simpler. If you insist on steel, a HEA 160 beam could be suitable, but it will be significantly more expensive.

Thanks for the response Justus!

Is there a beam that is really strong and can bear a lot without deforming, thinking that there are HEA, HEB etc.

The opening will be 4 m, it is an inner wall. The house is 7500 m wide, and the wall is in the middle. Room height is 240. Roof slope 23 degrees. Those were the details I had to enter in the tool here: https://www.byggbeskrivningar.se/dimensionering/oppning-innervagg-2-planshus/

I agree that a 140*315 beam would look nicer than 90*360, but a steel beam might be better, even if it costs more.

Is it possible to calculate a steel beam with this information? Is there a tool I can use?

Thanks for all the answers, really appreciated!

 

[Stefan1972]

Generally speaking, it is probably a misconception that steel beams are stronger than wood just because they are made of steel. A steel beam that is dimensioned not to buckle very slightly is usually quite tall.

 

[EliasAphram]

In general, it is probably a misconception that steel beams would be stronger than wood just because they are made of steel. A steel beam that is designed to not buckle very little often becomes quite high.

It's not about the steel beam being stronger, I've heard and read that this is not the case. Here it's about getting as little sagging as possible.

 

[Stefan1972]

It's not about the steel beam being stronger; I've heard and read that this is not the case. It's about achieving as little deflection as possible.

This wasn't directed solely at you but just as a general comment. Now, I'm not an engineer, but if you look at normal beams and a span of 4m, you might need to use a 200-300mm high beam just considering the beam's own weight if you want to avoid sag. Then there's the load on top of that as well.....

 

[f91jsw]

It wasn't directed only at you but just as a general comment. Now I'm not a designer but looking at normal beams with a span of 4m, you might have to go up to 200-300mm high beams if you just consider the beam's own weight if you want to avoid sag. Then, there's the load to add as well.....

We installed a HEA160 with a span of 480 cm. It supports existing rafters as well as half of the extension's roof via a column placed in the middle of the beam, which in turn supports the extension's ridge beam. The deflection is 13 mm according to the designer. It is not visible to the eye unless you stand on a ladder and look along the beam.

So I don't quite agree that you need high beams.

 

[witten]

The deformation of 13 mm indicated by your designer occurs at 70% of the design snow load, so there must be a significant amount of snow on the roof for you to be able to see it with the naked eye.

 

[Stefan1972]

We installed a HEA160 with a span of 480 cm. It supports existing roof trusses as well as half of the extension's roof via a column that stands in the middle of the beam and in turn supports the extension's ridge beam. The deflection is 13 mm according to the engineer. It is not visible to the eye unless you stand on a ladder and look along the beam.

So I don't quite agree that one must have high beams.

Absolutely, but I got the impression that the OP wanted something that didn't sag at all and thought that a beam would solve the matter compared to a similar wood. You also have a column in the middle of the beam, it sounds like?