reinforced concrete column ties

What tie pattern is suggested for round column. I have seen circular tie with 135 degree hooks at each end and have also seen circular ties where the ends overlap one another. Is the style a contractor preference or a code requirement?

 

[whyun]

I'd prefer to use a spiral tie for round columns. If requested as an option, I had used the circular ties with a 135 degree hook. I am not sure if it is allowed in California but I would stay away from lap splices for the ties. just because.

 

[Qshake]

Spiral ties are best for round columns but they have special terminal requirements too. Look in ACI chapter 21 or the reinforcing chapter.

 

[Kramer]

This brings up a question I have. I design a lot of light frame structures in Caliornia (seismic zone 4) with drilled pier foundation due to expansive soils and/or hillside locations. I often give contractors the option of using spirals for cast in place pier reinforcing instead of square ties. Section 1907.10.4.4 of the 1997 UBC calls for one and one-half extra turns at each end of the spiral unit. Section 1921 defines a "hoop" as a closed tie or continuously wound tie. It goes on to say that a continuously wound tie shall have a seismic hook at both ends. Does this apply to spirals used for piers? The seismic hooks get in the way of the hose when the concrete is pumped into the piers.