Precast Column Attachment

[JStructsteel]

Have a precast job, working on a entrance way to a building. They are using precast beams and columns to support the entryway.

The question I have is the precaster wants to make the columns in pieces. The top is a 1'-0" piece, then a 6 foot piece on a 2'-0" piece at the bottom. I see why they want to break it up, forming it in 1 piece would be horrendous. They are proposing to join it all together with threaded rods in one piece and grouted to the next.

I have no uplift, and moment is minimal. The beams are concentric at the top, but would consider some accidental eccentricity.

The connections take the shear fine, I am questioning stability. Im worried if someone hits them with a car, etc.

Thoughts?

 

[KootK]

I see why they want to break it up, forming it in 1 piece would be horrendous.

I don't see why that would be horrendous. There must be something missing from your description of the situation?

The connections take the shear fine, I am questioning stability.

These connections can take certainly moment if they are designed with that intent in mind. Certainly, you'd have stiffness discontinuities at each joint that would be tough to assess accurately. I wouldn't sweat it for something with minimal axial load though. Behavior would probably be governed by stiffness in the 6' segment anyhow.

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.

 

[JStructsteel]

KootK
Its a architectural piece too, square pieces and round pieces, all in same column. I will ask why they are doing it.

its well over designed, almost 2'-0" dia for maybe 10-20K load. Its more for the architecural look. Usually its a steel post with cladding, this time all precast.

Thanks

 

[KootK]

square pieces and round pieces, all in same column. I will ask why they are doing it.

Sounds like that's probably our answer. I don't think that there's anything much to be worried about here.

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.

 

[dik]

Will the joints be unobtrusive? Short term and long term? Send a note to the architect saying that there are no engineering exceptions... does he have any?

Dik

 

[TehMightyEngineer]

Why can't they just do it in separate pours? Pour the 6' piece with rebar protruding from the ends then form and pour the ends? Should be easier than putting in conduit and threaded rods and having to assemble everything. Easier to lift and handle as well.

Still, I agree with the above; this should be doable with threaded rod if they want to go that route.

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

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