Routing MVHR through universal beams?

[cjard]

the beam and joist layout for my timber frame is effectively (when looking at the top down 2d plans) steel universal beams on the y axis and joists between on the x axis. The house kinda looks like a noughts and crosses grid with the utility room in the middle. If this is where the MVHR unit sits (in square 5) then it probably makes sense to have the MVHR ducting go on the y axis into squares 2 and 8 then branch out into the corner squares.. But to do so it will have to pass through the universal beams that are the "grid lines"

So, my query is, does this happen? Can a steel support such a significant diameter (100mm+) hole in its web? If not what is the method for traversing these beams?

 

[bernardgreen]

Very large holes can be cut in the web of an I beam without significantly weakening the beam.

http://www.optimalbeams.com/tartok_en.html

 

[SimonH2]

More correctly, cutting big holes in the web will weaken the beam. Cutting big holes in a beam can make for a more efficient beam (weight of beam/load supported) provided it's designed that way in the first place.

If you were needing to cut big holes in the web of a beam, then ideally it should be done slap bang in the middle - assuming reasonably uniform loading. In the middle of the span, the stresses are tension/compression of the flanges with the web there basically to hold the flanges in the right place ! The worst place to cut large holes is towards the ends - here the load is taken primarily as shear in the web with the flanges there to keep the web in place.

I would suggest that you shouldn't cut big holes (big enough for meaningful ducting sizes) without getting the structural engineer to confirm (in writing) that it won't compromise the structure.

 

[Paulg31]

As above holes can be formed in the webs of UB's however they will affect the load bearing capacity, especially in areas of high shear eg close to supports. I'd suggest first confiming the size hole you require and getting it checked by a Structiral Engineer. Also as above I'd centre the hole along the centre of the web.

 

[SimonH2]

There's a good diagram about half way down this page :
http://fet.uwe.ac.uk/conweb/commercial/ironandsteel/section1.htm