Beam strength

[gasmaneddie]

My daughters house has steel beam spanning approximately 5M in the kitchen and presumably supporting the first floor elevation, Cant see at the moment exactly how deep the beam is but thinking it may not be much as there is a pillar in the centre of the span presumably supporting the beam along half its span.
There is already limited head room in the kitchen so increasing the beam depth by even say 2" would not be ideal.
My question is if the beam width was increased would that afford more support strength? or does it not work like that.
Obviously they would need to appoint a builder and structural engineer etc. but just curious

 

[^woody^]

It's mainly depth but also section size (ie thickness) and then width that matters.

But why would this beam randomly need widening?

 

[Notch7]

But why would this beam randomly need widening?

bifolds perhaps?

only a SE will be able to give you a real answer.

sometimes universal columns are used as beams they are more square in section which might reduce the height, same also is true of the steel thickness.

is the existing steel flush with the ceiling or set below

 

[John D v2.0]

Are you wanting to get rid of the column or something? Or some other issue?

 

[gasmaneddie]

The current beam is flush with the ceiling, The reason for removal would be to remove the central pier which at present has been boxed out with plaster board to accommodate mains pipes and soil pipe etc. It therefor is a rather large obstacle in the centre of the kitchen making it very impractical to design around and enjoy the space

 

[^woody^]

I doubt anyone with any sense would lift a 5m beam in and use a central pier. Is it not 2 x 2.5m beams?

 

[^woody^]

bifolds perhaps?

Surely that would be lengthening?

 

[tony1851]

For a 5m clear span, one of the Universal Columns sections would do, as Notch pointed out. A practical size would be one of the 203 x 203 sections - they are available in 5 different weights. Depth is obviously an important factor regarding deflection, as that other guy pointed out,
but the heavier UC sections have thicker flanges which help.
If it is supporting a cavity wall, you would need a 250 wide by 6 thick plate tack-welded on top to provide the width.

 

[Leofric]

I realise you are just making preliminary enquiries but, as you say, you need a structural engineer to design it .They will take into account the loadings and structural details of the situation which nobody on here can really know without visiting the site or a lot more information about the structure of the house.

 

[Notch7]

soil pipe etc

That could a real headache to relocate.

Although your avatar suggests you might already know what to do

 

[Leofric]

That could a real headache to relocate.

Exactly. Start with how you are going to rearrange the above ground drainage before any structural design involved in removing the pier.

 

[gasmaneddie]

No problem for me relocating the services (Probably ), I have no intention whatsoever in the structural work was just curious for information on the physics of beam strengths with re guard to width , size & thickness of steel etc.

 

[John D v2.0]

the physics is really complicated and covers lots of areas, but as our SE explained to me, bascically the deflection is usually the problem for houses, not the strength. For a simple wooden beam if you multiply the width of the beam by the cube of the height, you get the stiffness, and the deflection is something around the cube of the span. So you can help things by making the beam wider, but it would get silly quickly, but in general a rule of thumb is if you double the span you double the depth.

There are also problems to overcome where the beam twists in the middle, so you need to restrain it or make it bigger. For joists in floors the standard practice is to brace with solid blocking but for beams they are often alone so they have to do it by themselves.

For steel it can carry much higher loads than timber, but it's very heavy and expensive, so they shape it into UB shapes which are the most efficient by cost for conventional tasks. They just take out all the steel in the middle that's not providing maximum benefit. However in domestic situations headroom is more important so UC can be used which can be made shallower.

Generally if you can get away with it you want to make things out of timber, but often you have to include some steel in the mix for large openings/lots of masonry above.

That's about the limit of my knowledge, I'm sure we will both learn more from subsequent posters!