drilled pier ties spacing 3

[DoubleStud]

I was told that maximum spacing of ties shall be minimum of the following:
1. 16 X of the longit. bar dia.
2. 48 X of the tie bar dia.
3. pier dia.

This is what I was told in the past. But I can't seem to find this reference anywhere. Is this shown anywhere on ACI? My initial calculation shows that I dont need shear reinforcement. Vc alone will suffice. I just want to put minimum ties.

 

[JedClampett]

In ACI 318-14, it's in 25.7.2.1.

 

[JedClampett]

In looking at your post, you seem to be talking about column ties, not beam stirrups. Simply, but not always, ties are required for column integrity and stirrups are required for beam shear.

 

[DoubleStud]

It is foundation for an overhead crane in fat clay. The pier will resist moment.

 

[azcats]

JAE taught me years ago that ACI doesn't apply to drilled pier foundations.

But if you're resisting moment and shear near the top I'd treat it like a pedestal or column wrt minimum reinforcement. I'd also add a grid across the top (unless you've already got some sort of reinforced cap) that can resist at a minimum the shear demand.

 

[Aesur]

ACI318-14 says it doesn't apply for caissons embedded in ground expect for the portion that is supported by soil incapable of providing adequate lateral restraint and prevent buckling (1.4.6) or structures in SDC D, E or F. Caisson reinforcing is mentioned in 18.3.4.3 and refers you to 18.7.5.2 (a through e) and 18.7.5.3 and 18.7.5.4. When (not in SDC D-F) you are to use the 2018 IBC for design of the caisson, which basically says "reinforce" the caisson.

 

[BridgeSmith]

For drilled shafts, AKA caissons, AASHTO has a max spacing of spirals or ties of 6", and a minimum spacing of 5 times the maximum aggregate size in the concrete (so that the concrete will flow into the annular space without the aid of vibration).

Rod Smith, P.E., The artist formerly known as HotRod10

 

[DoubleStud]

Thanks Bridgesmith. So since this isn’t a highway project I assume I don’t have to follow that?

 

[BridgeSmith]

I just posted that for informational purposes. If your governing code is silent on the minimum spacing of reinforcing (the 5 times the max aggregate size applies to longitudinal also), it might be something to consider, though.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

I typically use 10M@3'-0 with 3-10M@6 top...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[BridgeSmith]

I typically use 10M@3'-0 with 3-10M@6 top...

For shafts not subjected to large lateral loads, that would work fine. That's rarely the case for bridge foundations. We typically have substantial moments down 20' or more, so we just carry the spiral (#4 or #5) at 6" pitch all the way to the bottom. In high seismic locations, per AASHTO, we specify a continuous spirals, or with welded or mechanical splices.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Concur, Bridgesmith... vert reinf is generally 1-15M and no ties... if 4-10M/15M, add ties as noted. Lateral loaded piles are a whole bunch different.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik