Dimensioning of steel beam

[Vempan]

Hello!

I'm considering using a UPE steel beam to support an opening in a 1+2/3 story residential house.

The opening is 3.0 m, and we have calculated a continuous load of 16.7 kN/m (total 50 kN) and a point load in the middle of 7 kN.

Is it possible to get advice on the choice of steel beam and information on how this calculation is done? I assume that deflection will be the critical factor, and I want it minimized.
Thankful for a response!
Thomas

 

[Enk Projektet]

Hello and welcome to Byggahus

I believe it is more common to use HEA/HEB beams when replacing load-bearing walls if you cannot use laminated timber.

 

[Vempan]

I agree that HEA/HEB beams are more common, but in this case, I want to change without having the beam under the joists. The idea is to recess the joists into the UPE beam to avoid a visible beam. On the other side of the beam, a pitched roof begins, and therefore UPE fits better than HEA/HEB!

 

[mdab]

You need a UPE 180.
What you need to consider is directing the forces towards the center of mass. With an HEA or IPE, it is simple because the center of mass is in the middle. If the forces do not act at the center of mass, you have an eccentric load and the beam can twist.
Cy in the attached image shows the distance to the center of mass. For a UPE 180, that distance is 24.7mm.

View attachment Ny bitmappsbild.bmp

 

[hempularen]

Now I'm not an engineer, but I don't quite understand why it would be better to recess the beams into a UPE beam than into a HEA?

 

[Vempan]

Thanks mdab! What deflection would a UPE 180 have? Since the beams are 195mm, I was thinking of possibly oversizing the beam to UPE 220 since the beams would then fit "within" the U-beam. Then I considered screwing them at the back through the beam's web, which should prevent the beam from twisting, do you agree?

hempularen: The beams won't be easier to fit in, but I don't want to have the flanges "out in" the new room section (which is only one-story and therefore doesn't have an intermediate floor) since I'm going to have a vaulted ceiling there, and I would then need to "thicken" the wall further in that direction to cover the flanges!

 

[Granngubben]

If the forces do not act in the center of mass, you have an eccentric load and the beam can twist.
[attached file]

I would assert that the force should act at the shear center (SC) to prevent twisting. The shear center and the center of mass coincide in many cross-section types, but not in U-beams.

Securing the beams in the web, as TS wants to do, prevents twisting.

 

[peternicklas]

I would probably choose a square or rectangular tube instead. For a UPE beam, it is the SC that applies for twisting. It is outside the geometry of the beam and is therefore more difficult to work with.

 

[mdab]

My mistake. It is SC and not MC that the force should act through. I apologize for that.
But if you tighten at the back, you minimize the twisting. If you also go up to upe 220, you don't need to worry. But sure, generally, it is always preferable to use symmetrical cross-sections.