7 meter (23 feet) beam - simply supported - split in half and then welded on site - Any Concerns?

[dacdacdac]

Hello, I'm looking at a construct-ability problem.

We need a structural beam that spans 23 feet at a residential home, its fairly heavy beam for a home, w10x10 or W250x73. The problem is that we want to work indoors, and to do that we would have to cut the beam in half, jack it and do a full moment weld connection midspan.

I'm curious if there are any alternatives or concerns with this approach?

Thanks in advance!

 

[dacdacdac]

I realized that the welding does not need to occur until after we have cut the back of the house open. That being said, I'm not against bolting, I just keep hearing we wont get reliable cut outs from the fabricator for something like this... might be my contractor is not trying hard enough.

Your vision of what i'm doing is close, but its a bigger addition than that, we are adding 14". I wrongly typed it was a 100sqft addition, meant to say 1000sqft or 330 sqft per floor (including basement), I've attached a plan and section drawing.

This last one is a picture of the house right now.

 

[dacdacdac]

Drawings1
Drawings2
Drawings3
Photos4

The dimensions are there. Loads are residential and roof loads (snow loads).
- FIRST, SECOND AND THIRD FLOORS
OCCUPANCY: LL = 1.9 KPa
- FLOOR LOADS: DL = 0.75 KPa
- ROOF/DECK SNOW: SL = 1.00 KPa
- ROOF DECK: LL = 4.8 KPa

 

[Triangled]

great info. a lot bigger project than i envisioned, that's for sure.......

so, your proposed beam is at the top floor level, supporting the bedroom floor joists, balcony joists, exterior wall and roof?
and the photo is from the inside of the living room looking up?

 

[a2mfk]

As much attention as you are paying to this steel beam, pay more attention to that open deck that you have over enclosed space. I've made some good money looking at water damage to those types of structures, and a coworker just discovered they have about $20k worth of water rot damage to their relatively new home with an open deck over a lanai very similar to your detail.

Manage the water drainage or it will manage to drive you crazy...

Have you run some calcs on multiple plys of engineered wood as others have suggested? What kind of numbers are you getting?

 

[AELLC]

I am getting 1 KPa = 48 psf, so there must be something wrong with my conversion.

Also, you say Roof Deck LL = 4.8 KPa, and Floor LL = 1.9 KPa, therefore the ratio is 2.5 which translates the same as if I used 100 psf for roof deck LL and 40 psf for floor LL in English units.

However I believe 100 psf live for a large residential deck is conservative - it should be residential floor LL x 1.5 = 60 psf.

 

[AELLC]

Also, if this is Canada, why is the snow load so small?

 

[AELLC]

See detail.

 

[dacdacdac]

a2mfk: I'm definitely going to give some thought on the deck details. I'm still not sure if we are going to go with a floating deck structure or duradek style roofing.

AELLC: You are right that snow load is wrong, it should be 1.12kPa (23psf), which is Toronto's minimal snow loading, at the accumulation points i believe it reaches 50psf (2.4kpa)

All: Thanks for all the advise, the more i'm looking at it the more I feel I should go with a wood framing option with a column in the middle. Probably leaving the wood post exposed. Spanning the full 7m with wood while possible would require a beam depth of 19in, a PSL 19"x5", which might also work exposed but due to the roof deck above I'm not sure that is a great idea.

Triangled: Yes to all your questions. The beam is at the top floor level, supporting the bedroom floor joists, deck joists, exterior wall and roof. Noted near item 23 on this drawings: Link

 

[AELLC]

Still, 1.12 KPa for snow looks way too small. The snow will drift against the wall.

 

[AELLC]

dac-

You REALLY need to hire a local struct engr. When I saw the words "beam bearing on brick wall..." that raised all kinds of red flag.

If you don't want to pay mega-dollars for a regular firm, try finding a one-person operation maybe by going online to to your Provincial Board of Registration for Engineers.

 

[dacdacdac]

Thanks for the concern. I am planning on doing a 3rd party review of everything

​

with a colleague.

"Beam bearing on brick wall..." was an over simplification. I meant to express my concerns with the brick wall the support post are bearing on. The bearing connections will be with steel plates and proper anchorage, or a concrete bearing pocket.

 

[AELLC]

Even so, is this proper load bearing brick?
Also, with a proper brg plate the brick overall may buckle with compression load.

Overall, looking at your dwgs and pic, I still say you should invest a bit in a licensed PE or SE

 

[A4North]

Snow load (unmodified and unfactored) for toronto is actually 0.9kPa, special consideration would have to be taken here for snow build up on the balcony. Lateral bracing requirements would probably be minimal since it's an upper storey.

Have you considered hanging the existing joists from a new timber beam (most likely a couple of LVLS)? This would greatly reduce your bulkhead and in-fact since you will have a 'step' directly above (for the balcony door) you can use that additional space to your advantage. You'd have to jack the existing floor and reduce the length of the existing joists. A timber beam would not require any machinery for placement.

Cutting up a steel beam will still leave you with extremely heavy lengths so you are going to require a machine to place it regardless.

I can size the beam for you according to the OBC, i'm in the GTA.

 

[dik]

Your beam will only be as good as the weld... and welding it in the middle will be near the location of maximum stress.

If you can get half the beam in place, you may want to consider cutting the one half length into half again. This gives you twice as much weld as two pieces and the welds are located at quarter points... likely in a region of lesser stress... you may not need full penetration welds.

Dik

 

[XR250]

You could also do a bolted moment splice if you can afford the extra depth for the plates and bolts.