Column Ties

[MotorCity]

I am reviewing a shop drawing where the detailer has shown the lateral ties for a square column as four individual pieces of rebar per tie (one bar on each side of the square tie). Each piece has a hook on each end and all of the reinforcement is enclosed by the ties.

This arrangement looked a little unusual to me. Does anyone know of any concerns or ACI requirements that would prohibit this arrangement?

 

[jike]

I would think that the column cage would have more of a tendency to fold over on itself (kind of like a pinned-pinned structure with no x-bracing) because it doesn't have the rigidity of the continuous perimeter tie. Someone would have to add numerous mini-x-bracing in the plane of the ties to keep the cage rigid during handling and pouring. These mini-x-bracing rods or tie wires may cause the concrete to segregate as it is dropped in the form.

I would think that the GC would not be very happy about this situation.

I would require the perimeter tie to be continuous.

 

[JAE]

Rigidly interpreting ACI 7.10.5 what you describe appears to be acceptable - The only thing found in that ACI section is in the commentary where they say that stirrup hooks should be staggered "where possible" - which is not possible in your case.

We have used this kind of tie for interior bars with columns of 8 or 12 bars (with > 6" clear space between bars) where one end hook is a "J" hook and the other end a standard 90 degree hook. The thought is that we try to get as much hook as we can by using the J and this allows installation by hooking the J around the long. bar and then rotating the 90 deg. hook onto the other bar.