Cutting and splicing a column during construction

[canwesteng]

For constructability, I would like to chop a column in half, move a large piece of equipment into the building, and splice the column back together. Surely this has been done before, but the one problem I can't get my head around is that the column will be a little shorter due to material removed when cutting it. Should the contractor be able to make a clean cut such that this is minimal or is this a legit concern?

 

[TehMightyEngineer]

You'll lose material. Welded splice plates would be the way to go.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[canwesteng]

I think the buy-in for welded splice plates will be hard to get, cost and construction time wise. I might propose chopping ~2' of column out and splicing in a new 2' column section. It's an interior column in a braced frame, so no moment to speak of just axial.

 

[KootK]

Is there an opportunity to make up the length with extra grout at the base? Or a shim plate at the top?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[canwesteng]

My concern is that the intermediate members (column is braced for its entire height) won't re-connect properly with a shim. That was my first thought though, and the easiest solution.

 

[KootK]

Designed properly, you could use bolted (or welded) splice plates with an intentional gap to compensate for the lost material. I'd do this near a braced point rather than midway between braced points.

I don't love the 2' removal proposal unless I'm misunderstanding it, or it would be full pen welded back into place. In these situations, I always have some concern for not just the strength of the splice but the flexural stiffness of it as well (buckling). Installing two bolted plate splices in close proximity doesn't appeal to me on that basis.


I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

What size column are we talking about here?

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[slickdeals]

What is holding up the floor or roof while you chop this column?

 

[dik]

Slickdeals has it... time to shore up the existing roof/floor, cut as much of the column away as you need using a grinding saw. Replace the column as needed and reinforce using prepared welds and/or plates. KootK's idea of increasing the grout thickness to compensate for material removed is not to shabby if you have sufficient anchor rod projection.

Dik

 

[canwesteng]

TME - it's a W18 column...

slickdeals - Good intentions and fortune will hold up the roof during construction (joking aside the shoring is accounted for)

 

[KootK]

Peculiar column size, particularly for interior with no moments.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[SLTA]

Not so peculiar if it's industrial, and prone to getting run into.

Please remember: we're not all guys!

 

[canwesteng]

To satisfy curiosity, the columns are large in order to support a bin. We are chopping the columns to replace the bin.

 

[TehMightyEngineer]

That is a weird one. I still vote welded splice plates, I doubt you'll get much cheaper and easier than a couple of plates and fillet welds and then you save time by allowing the contractor to just torch out the column without worrying about the material loss and resulting surface profile.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[slickdeals]

If the column is in the way for the mechanical equipment, won't the shoring to hold up the floor be in the way as well?
I may be asking a stupid question totally different from your original questions.

 

[canwesteng]

The columns are real beefy, so no issue with bolt bearing, so mag drilling some holes for 1" bolts (could go bigger even) is probably better than elevated welding. Aerial platform welding on site involves a crew of 3, plus 2 hour fire watch, plus permitting, plus grinding and painting, and then weld inspection.

 

[TehMightyEngineer]

Welded-bolted splice plate then, weld to the cut part in a fab shop and field bolt to the existing. The millwrongs I worked with hated field drilling for splice plates as a welded plate will always fit whereas the bolted plate needs to have accurate field drilling to ensure no issue.

What weld inspection? Bigger the gob, better the job.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/