Torch Cut Bolt HOles

[bigmig]

Is there a code provision outlining procedure (or disallowing) bolt holes that are field fabricated by torch.....
Basically just blasting a horrible hole through steel for purposes of bolting.

Thanks.

 

[jittles]

Thermally cut holes are technically allowed, but with a bunch of limitations. If it's a "horrible hole" then it certainly would not be permitted. Surface roughness of the hole is one of the limitations.

The RCSC in the back of the AISC steel manual has the details.

 

[oldestguy]

One of my Cornell U. structural engineering professors (from Germany) demonstrated to us that the so called grip of a bolt or rivet between two steel plates comes about due to the friction grip between the two plates that is greater than the shear resistance of the bolt or rivet. Meaning the condition of the hole means little.

 

[dauwerda]

oldestguy, it sounds like you are describing a slip-critical connection (which does allow for the use of oversized holes), however a more typical bearing type connection absolutely depends on the interface between the hole and the bolt.

Section 3.3 of the RCSC addresses thermally cut holes, keep in mind they would still have to meet the size requirements listed as well.

 

[canwesteng]

If it's tension only, you can use some oversize plate washers. Otherwise you probably need to plug weld the holes and redrill. With a mag drill, like a real contractor and not someone messing around in their garage.

 

[EZBuilding]

If you can't trust the contractor to know not to cut a hole with a torch in the field, you should not trust him to produce a slip critical connection.

 

[Ron]

Flame cut holes are acceptable if reamed afterward.


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[Lomarandil]

I've known some ironworkers able to produce really nice and clean bolt holes with a torch. (A little out of round, but not enough to affect ultimate load distribution in my judgement).

For a tension bolt, my personal judgement is to allow it in almost all cases. Allow for washers or grinding the edges flat if needed.

For a shear bolt, I'd allow it in most temporary, low demand situations (given some level of contractor competence). If you're more concerned, underburn and ream to size like Ron suggests.

If your situation is aesthetically exposed, very thick base metal (over 3/4"), fracture critical, questionable inspections, or high-liability, then require a bolt hole that meets RCSC (however the contractor chooses to get there).

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just call me Lo.