Bolting a steel beam to another steel beam.

[vincentianpinner]

I'm talking about applying a modest pressure to the nuts without spraining the beam and then fully tighten them afterwards. What do you think might happen, lol?

When you did tighten them up did you do it to a particular torque? My fabricator reckons that's all a lot of s***e.

 

[noseall]

When you did tighten them up did you do it to a particular torque? My fabricator reckons that's all a lot of ****e.

Not especially. The bolts were quite snug and 'pinned' the beam securely without the nuts - i.e. there was very little movement once all four bolts were through. Make sure you have wiggle room as you offer the two beams together, as you need that bit of play to feed the bolts through. Get all four bolts through and nuts started and then crank them up.

 

[stevie888]

When you did tighten them up did you do it to a particular torque? My fabricator reckons that's all a lot of s***e.

All that's normally required with bolted joints is sensibly tight: no 6foot scaffold poles!

However there are occassions where bolts do have to be tightened very precisely. This is where HSFG bolts are specified: these are very strong bolts (which usually have a reduced diameter shank) and they work by pulling the mating surfaces together so tightly that high frictional forces develop.

They are common in steel frame structures but I have come across them once in a domestic environment. This one didn't end too well as the builder didn't understand what he was supposed to do and the steel sagged when unpropped and a lot of reworking was needed.

So your fabricator is right in your case but not neccessarily in general.

 

[noseall]

once in a domestic environment. This one didn't end too well as the builder didn't understand what he was supposed to do and the steel sagged when unpropped and a lot of reworking was needed.

You mean the steel was under sized? Our beam simply could not move at the joint, whether the nuts were cranked up really tight or not. Their was zero play. The holes in your scenario would need to be incredibly baggy, and the nuts actually loose? Sounds like a poor job all round.

 

[stevie888]

You mean the steel was under sized? Our beam simply could not move at the joint, whether the nuts were cranked up really tight or not. Their was zero play. The holes in your scenario would need to be incredibly baggy, and the nuts actually loose? Sounds like a poor job all round.

What happens with these joints is that the mating surfaces are supposed to be perfectly clean steel to allow maximum frictional forces to build up. The fabricator had simply slobbered red oxide over everything and the builder didn't appreciate that this would have to be carefully cleaned off to enable the joint to work properly as its presence provides a lubricant. It was a splice plate design in the middle of a long span and even a fraction of a mm play in the bolt holes would, and did, allow noticeable deflection

The main failure in my view here was the SE failing to apply the KISS principle to design by specifying a detail that whilst normal for experienced steel erectors was completely alien to a normal builder (this was a good builder, not a cowboy)