Field Torch Cutting Beam Flanges 1

[marinaman]

I've got a project where wide flange columns support wide flange beams.

The girder wide flange members frame to the column web via bolted connections.

The erector calls and says that, in the shop, the flanges of the girders weren't coped back far enough to allow the perpendicular beams to be bolted into place (girder flange is in the way of the bolts for the beams coming into column at the column flanges).

He wants to field torch the girder flanges to give him room to bolt the other beams to the column.

I do not like field torching.....but it may be ok here. I know torching changes the steel properties, leaves an ugly irregular edge, etc....but for the first 4" of a girder flange, this may be ok, as there's no load here.

What do you guys think?

 

[phamENG]

I've always thought the big problem with torch cutting was at bolt holes, since the issues you mentioned could completely negate a bearing bolt design. I'd be inclined to allow it, but be sure to specify tolerances for the cut. And I'd want to inspect the first one before I let them go nuts on an entire project's steel package. I might also consider having them grind it smooth, but that may not be needed.

 

[KootK]

I would also be inclined to allow this. It does change the nearby metallurgical properties. However:

1) It's an acceptable method in the shop where, albeit, mechanical guidance is preferred.

2) Steel's inherent material ductility makes much possible that otherwise would not be.

 

[Dvdt18]

Marinaman, unsure if this is helpful but here's some other threads with similar discussions

https://www.eng-tips.com/viewthread.cfm?qid=198807

https://www.eng-tips.com/viewthread.cfm?qid=321319

https://www.eng-tips.com/viewthread.cfm?qid=210234

Thanks,

 

[wannabeSE]

AISC has some FAQs with information on thermal cutting with oxy-acetylene . See

https://www.aisc.org/steel-solutions-center/engineering-faqs/2.2.-cutting-and-finishing-steel/

 

[ldeem]

It sounds like only one or two bolts are obstructed. If you are the EOR you could look at the connections and maybe get away with one or two fewer bolts in those locations. It may be tempting to substitute stronger bolts for connections that will be missing a bolt but they will require very good quality control. If you had to go this route I would require an inspection of every connection where higher strength bolts are needed.

As for torching I would be concerned about how much flange they will cut out and how close they will get to the web. Of course stress concentrations and fatigue may also be a concern depending on the situation.