Joining UB

[Domdom]

Quick question to those in the know. Fabricating the steel frame for the new workshop/garage and I’ve hit a small challenge.

The original plan was to have it 5.3 metres wide as the longest length of steel I have is 4880 (add the 10mm plates each end and the uprights at 203mm each. But that was going to waste almost a metre of potential width space which seems a shame.

So, rather than buy more of this UB (203x133x25.1kg) I was thinking about welding a bit on to the 3 horizontal beams to get them from 4880 to 5574mm. The plan was to butt weld the ends together and them weld a 8mm long plate in the web/gusset on both sides, but how long would that plate need to be?

These 3 beams will be holding the weight of a timber and felt roof which will sit on timber trusses so not a massive load. I just can’t find anything which will help me calculate this, probably cos it’s, ahem, less than desirable. Technically I think one is supposed to weld joining plates on the ends and then bolt them together.

 

[Rrobson]

Sounds like a recipe for disaster to me. Don't get me wrong, beams have been joins together for years, look at any large overhead crane that's more than 50 years old, it will be sections riveted together but can you guarantee a structural weld? Beams load should also be calculated, so will the addition compromise the carrying capacity of the beam? You might better with a bolted joint using suitable fish plates? That way your not potentially altering the metal structure adjacent to the weld? Provided the beam is up to the job in its extended state? Lots of ifs buts and maybes.

Personally I'd buy the correct length and flog the steel you've got. You'll probably recoup most of the cost anyway. But chances are there's someone on here who'll know either way!

 

[mtt.tr]

Not something that can be answered without an engineer, we've have them done before and we are supplied full details of weld spec

 

[Matchless]

remember I am a bodger but still have all my fingers and toes, I would weld it together provided you have a decent welder, then bolt a plate top and bottom for a mechanical joint, 8mm in shear sounds good to me, say 10 inches long to get say 10 bolts each side, hard for me to visualise but I usually say if it looks right it is probably over engineered,
35 years ago when building a side extension to my first house, end of terrace triangular plot, garage on the ground floor, two rooms above, I ponced an RSJ or UB for the front over the garage door from a shop demolition locally, maybe 9 foot long, massive, web was an inch thick, 12" tall, 10" wide from memory, the bit I cut off made a good anvil, I had to buy a NEW ub for the rear to support the upper 9" blockwork and roof above, that one was something like 16 foot long and came out 1/4" thick and 6" by 7" , I got the guy to recalculate it as I would have never used something that flimsy, one day someone will demolish it and find that two ton beam ………….

 

[Pete.]

Our guys are installing a beam at work that was made in two pieces to go in the goods lift and bolted together in situ. It's designed to carry a 100 tonne point load near one end.

 

[Welderpaul]

Butting it together end to end and welding is a bit of a no no really. Putting a splice in there is common practice and you'll probably find a standard splice detail for a 203*133*25UB without too much searching.
It will have a plate top and bottom on the flanges and plates either side of the web.

 

[Domdom]

Got it sussed now. Good pointer from @Welderpaul as I found an example of a proper splice joint with a calculator as well. That’s what I’ll be doing. It does help that it will be close to one of the ends so the moment is coming out at 38% rather than 100% if it was in the middle and, since this steel was almost free I didn’t get to choose the size. Architect reckons it would have been 152 x 89 x 16kg so I’m well over that with 203 x 133 x 25kg.

Quite interesting to see a bolted plate is stronger than a welded one. The bolts create a friction joint across the whole surface of the plate but a weld round the edges doesn’t. Of course, the “over-engineer everything” in me says bolt it up and then weld round the edges