Ties in Round Columns 1

[PEFLWI]

Recently I specified drilled piers (caissons)for foundations. Because the piers are round, I also specified round ties around the vertical bars. See the attached drawing. The round ties varied quite a bit in diameter. This made it difficult for the contractor to get the vertical bars in the corners of the bent bars and keep equal spacing of the vertical bars. This variability in the ties also made it difficult for the contractor to install the anchor rods with adequate spacing from the vertical bars. It seems to me that the fabricator did not fabricate with adequate precision. Does anyone know what the tolerance is for the diameter of round ties?

 

[PEFLWI]

Attachment

 

[jayrod12]

your contractor needs a new reinforcing supplier if they're that off. I've never had that issue.

I would expect however that any sort of tolerances would either be in the applicable ASTM (or CSA or BS etc.) standard for reinforcing steel. CRSI may have some information on this as well.

 

[SlideRuleEra]

From CRSI Construction Technical Note referring to ACI 117 and CRSI Manual of Standard Practice.

http://www.SlideRuleEra.net

 

[hokie66]

Poor fabrication. But for your next drilled pier project, consider spirals. Cages are much easier to build and are more stable for insertion into the holes when made with spirals. Surprised that your contractor did not request a change.

 

[skeletron]

I've had a similar problem before. Usually they can't the vertical bars right in the corner and it's a little bit off. If you are working with a skeleton crew, this can happen occasionally. They always seem to raise a stink about how hard it is to bend the bar 135deg because of the sequence of the bending. Anyways, it sucked.

 

[PEFLWI]

jayrod12, SlideRuleEra, hokie66 & skeletron:
Thanks for your thoughts.

SlideRule Era:

Thanks for the link!

hokie66:
If you use spiral ties, how do meet the ACI requirement for (2) ties in the top 5 inches? Do you use separate ties for those?

 

[hokie66]

No separate ties required. You just use several winds of the spiral. In other words, you reduce the pitch of the spiral at the top. But if you want, you can use separate ties there.

 

[PEFLWI]

hokie66:
Thanks.