Old Metal Building KL/r >300
Old Metal Building KL/r >300
(OP)
I looked at an old metal building today where the owner wants to remove one of the gable end columns. The gable end wall paneling was removed and a new metal building was added next to the existing metal building. We discussed adding a new structural member and posting down with some new columns/footings.
I can come up with something that will work, but my question is about the existing construction. The end wall columns have a kl/r of over 300. I looked at the column capacity and the girder capacity and they both can handle about 19-20 psf of TOTAL gravity load for the roof. IBC Roof Live load reduction is 18.5psf. So that leaves the building with about 1 psf for all of the dead load.
I also noticed that the new metal building next to the old one had much larger member sizes for columns/beams that had fairly similar bay spacings.
I'm concerned about the liability and thinking about telling him to look elsewhere for advice. Thoughts?
Thanks!
I can come up with something that will work, but my question is about the existing construction. The end wall columns have a kl/r of over 300. I looked at the column capacity and the girder capacity and they both can handle about 19-20 psf of TOTAL gravity load for the roof. IBC Roof Live load reduction is 18.5psf. So that leaves the building with about 1 psf for all of the dead load.
I also noticed that the new metal building next to the old one had much larger member sizes for columns/beams that had fairly similar bay spacings.
I'm concerned about the liability and thinking about telling him to look elsewhere for advice. Thoughts?
Thanks!






RE: Old Metal Building KL/r >300
Owners need to be educated that metal buildings are fine until you need to change them. As long as there's never any chance that they'll be remodeled, they're the way to go.
I just attended a webinar by Alexander Newman of ASCE on Remodeling Metal Buildings. I advise you check it out.
RE: Old Metal Building KL/r >300
Telling him to find another engineer does not relieve you of your responsibility to report a condition which you know to be unsafe.
BA
RE: Old Metal Building KL/r >300
Garth Dreger PE
AZ Phoenix area
RE: Old Metal Building KL/r >300
Where's the "l" ends? At the connection? At the top?
Could the girts be assumed as column bracing?
Might the top be considered fixed as far as axial spans?
How about the base plate? Could it be assumed fixed or partially fixed?
Just because you or I wouldn't stretch things that far doesn't mean it hasn't been done. Just don't go to the owner unless you're sure there's an issue. You don't want to cry wolf. If you're sure, than BAretired is right, you need to tell them.
RE: Old Metal Building KL/r >300
I'm going to refer the owner to an engineer experienced in metal buildings...
Thanks!
RE: Old Metal Building KL/r >300
1) Yes, there were probably diagonal brace rods or cables in the old endwall prior to the expansion. There is some possibility that the endwall sheeting was being considered as a diaphragm in lieu of rods, but since that is no longer there either, it doesn't make much difference either way. While this omission affects the lateral stability of the frame, it doesn't really resolve your original concern with l/r > 300 other than in the determination of an appropriate K.
2)The combination of girts and paneling is almost always used to provide lateral support points for the weak axis of the columns, particularly on light endwalls. Note that it is the combination that does the job, not just the girts. It is not unusual for someone to remove the paneling in a case like this and leave the girts and think they still have the same resistance that they did when the building was complete.
RE: Old Metal Building KL/r >300
RE: Old Metal Building KL/r >300
Did the owner load the existing end wall roof framing with new roof purlins?