Thermal Cutting in the Field
Thermal Cutting in the Field
(OP)
I have a structural steel project where the contractor is requesting to do some thermal cutting in the field, specifically to make the slot in HSS braces longer and/or wider. Our specs of course say that thermal cutting in the field is not allowed, but due to the quantities of steel and difficult nature of this particular project, they are asking if they can enlarge/ lengthen the slots in the HSS braces with thermal cutting to make erection easier because grinding "is taking too long." My biggest concern about the thermal cutting is the increased risk of stress concentrations, especially at the end of the slot beyond the gusset plate where there is no weld or gusset plate to reinforce the HSS brace. Has anyone allowed thermal cutting of major structural steel members in the field before, and if so, what additional constraints did you put on the practice for the contractor to follow and/or for the inspector to look for/ test? Thanks for any input that anyone may have to share.






RE: Thermal Cutting in the Field
Professional and Structural Engineer (ME, NH)
American Concrete Industries
www.americanconcrete.com
RE: Thermal Cutting in the Field
Some contractors do a pretty good job of it -- tough to distinguish from a shop hole. I don't know all the standards in play here, but certainly if they were able to produce a hole that met the AISC standard practice requirements, not an issue.
However, I've also seen many field and flame cut holes that don't even resemble round. Definite points of stress concentration rather than a smooth surface for the bolt to bear on. We've evaluated those on a case-by-case basis, taking into account connection demand and the magnitude of the irregularity. However, in a permanent design application, I'd suspect you would want to be more cautious.
Sorry I can't be more helpful here. In short, I wouldn't take it off the table, but you're right to put some extra thought into it.
RE: Thermal Cutting in the Field
RE: Thermal Cutting in the Field
The HSS is probably sized for compression buckling at the mid point and probably has lots of extra beef at the connection zones. It will probably look ugly, but if that doesn't matter, don't be unreasonable.