Jack Beam Splices

[PaulBPE]

Is anyone familiar with splices for "Jack Beams" in prefabricated steel frame structures? I am wondering if this was supposed to be a hinge. The beam is experiencing lateral-torsional buckling and I'm curious if these splices are problematic. In the attached pictures there is a W section bolted to the bottom flange of one the beams, but no positive connection to the beam on the left. Is this supposed to be a hinge?

 

[human909]

Buckling, ANY sort of buckling is almost always a problem. Fortunately we don't often see it in vertical members in most under designed structures. LTB is also a big issue but can often have enough redundant load paths to stop collapse.

Regarding this structure. I don't know where to start. It seems to have two splices next to each other which is bizarre. Possibly it wasn't in accordance with design in the first place.

Furthermore there really does seem to be very little restraint to LTB on that beam at all. No wonder it is screaming out in distress.


My advice. If your job is to look at this building. Look at it with FRESH eyes. Assume the original designer knew nothing. So if something is wrong, it probably IS.

PEMB's push the limits. But this seems already beyond the limits presumable with ulitimate limit state loads!

 

[Enable]

Super duper odd. It looks like the bolts in the web on one side of the splice are in slotted holes (hard to tell though). If this is the only location where this occurred I'm wondering if someone tried to use the lowered w-section as a hoisting point. Certainly would add some torsion (if load became uncentered) and add to LTB potential.

 

[lexpatrie]

We had a vaguely similar building here that I never got a good look at, (it got demolished and replaced). The buckling is not a good sign. If this is in a snow region did it "near miss" collapsing and now has permanent deformation, if not, somebody in the near term should make sure all the roof drains are clear and functioning. The splices also seem a bit adventurous.