Cutting small notch out of column

[Thoughtclaw]

I'm a pretty green engineer (got my PE in December) working for a small contractor. Our shop foreman came to me with the attached sketch. He wants to cut a 1.5-by-15-inch notch out of an existing W10x45 column, 23 inches above the bottom plate. I don't have any information handy about what the column is carrying, but I can certainly go out there and take a look at it. I'm inclined to think it's not going to affect the capacity much at all, since it's so close to the end of the column, but I thought I'd ask you folks if you have any thoughts about it before I sign off on it.

 

[Thoughtclaw]

I should add, the notch would only be cut out of one of the flanges.

 

[oldestguy]

Not enough info for a positive answer. Missing: loads, bolts, etc. My GUESS no problem.

 

[SlideRuleEra]

Thoughtclaw - Visit the site, IMHO, always do that if at all possible.

Do what it takes to get at least an idea of what loads the column carries and all connections (e.g. anchor bolt, beams framed into the column, etc.). Hopefully, drawings are available. If not use the site visit to make an estimate of the loads. How much the capacity of the column is reduced by the notch is of limited value if the magnitude of the loads is unknown.

During the site visit, check the condition of the column... pristine? ...corroded? ... bent or deformed (anywhere)?

What you find will determine what to do next.

http://www.SlideRuleEra.net

 

[Ron247]

The actual location of the notch relative to the ends of the column is another factor. The flange width/thickness is sometimes a function of unbraced length. To me, notching 23" from the bottom does not have the same impact as that same notch at the middle of a K=1 column that is say 18' tall.

 

[CANPRO]

Definitely get more info before making a decision - the column could have been undersized to begin with.

Since you're the engineer for the contractor, another thing to consider is who else might have something to say about this? Is there an EOR involved? Will the owner question this? The structural integrity of the column is only part of the consideration - if you approve the notch (even if structurally acceptable) and then the EOR or owner sees it and takes issue, your company might be on the hook for repairs regardless of what your judgment says. My advice - run the numbers to make sure its okay, then get approval from all involved who might have a say.

 

[Thoughtclaw]

Thanks for the prompt responses. I'm going out there early next week, and they're trying to find me a drawing.

They're talking about welding an angle to it just inside the notch, which would probably be adequate. But I still want to run the numbers, obviously.

 

[bridgebuster]

If you do notch it, no sharp corners & grind the cut edges smooth. The notched corner is a stress raiser.

I don’t trust ironworkers with torches and less so when they’re burning notches.

 

[chicopee]

If you do cut out a notch, explore about welding reinforcement plates on the three sides cut out which will mean removing more material than the original requirement. If you look at bridge tub girders constructed within the last 20 years, any opening made in their webs are reinforced.

 

[BUGGAR]

And make sure your weldors' certs are up to date and they have the proper WPS for this work. Might have to cut a bigger piece for a weld qualification test if they can't tell you about the specs on the steel. Might as well go all the way.

 

[Thoughtclaw]

Thank you all. All these comments have been very helpful.

 

[racookpe1978]

Well, the MAIN question you must answer is: "Why do you (the foreman) want to cut a notch out of the building's (owner's!) existing column?"

As above: "Where is the notch? How can you do your job without cutting the notch? Why should we (the contractor) pay extra design and engineering and assume the liability for the notch? Is there a cheaper/safer way to get the (whatever) done without cutting the owner's steel column?"

Can you add a reinforcement or plate over the notch opening after cutting the notch and installing the pipe (or whatever)- if it needs cutting at all? Much stronger than adding a sister plate reinforcement around the notch.

 

[GeorgeTheCivilEngineer]

Additionally, consider the detailing of how they do the notch. E.g., make sure they use rounded corners (suggest by drilling out the corners of the notch) and not going wild with an acetylene torch.

 

[racookpe1978]

Bump.