CSA A23.3 Spiral tie spacing requirements for piles
CSA A23.3 Spiral tie spacing requirements for piles
(OP)
Is anyone aware of a way to weasel out of the maximum spiral pitch in CSA A23.3? Specifically regarding clause 7.6.4.3 (7.6.4.4 in 2004), giving the max clear of 3". Contractors often want to use spirals for piles (understandable as they hold their shape well), but usually just suggest swapping tie spacing with spiral pitch. I'm thinking there must be a way to weasel out of this, otherwise why are yards even set up to make spirals at an 8"/10"/12" pitch?






RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
If only the tension capacity of the vertical reinforcement, then the spiral is only there as a placeholder and I don't think it needs to meet the confinement requirements.
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
By any chance is this a spirally reinforced column requirement rather than for bored piles? Bored piles are normally lightly loaded, as their size is dependent on the material they bear on at the bottom. So the reinforcement is typically light, and as Dik suggested, often not full length.
canwesteng, as the normal wire/bar used for spirals is relatively flexible, the spirals fold together, so you determine the pitch when you tie them. All the fabricator needs to know is the diameter and the number of turns you want.
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
However, using a continuous helical as tie reinforcing does not require that you design this as a spiral. ACI code (I'm assuming CSA is similar) allows you to use a larger pitch and classify the reinforcement as a circular tie rather than a spiral. (R7.10.5 ACI 318-11)
RE: CSA A23.3 Spiral tie spacing requirements for piles
Is that for columns? I tried to make the distinction above for the difference between columns and bored piles. Unless it has been changed, ACI318 does not apply to bored piles, unless in a high seismic area.
RE: CSA A23.3 Spiral tie spacing requirements for piles
I agree, does not need to apply to drilled piers.
RE: CSA A23.3 Spiral tie spacing requirements for piles
As an aside, if you are working in Canada, CSA A23.3 does apply to piles. It has some onerous requirements there as well, but that's off topic.
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
The tight spiral spacing is for confinement with colunms, not friction piles. I've designed friction piles where the top is unsupported by soil and have used regular column tie spacing.
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
canwesteng's question was about bored piles, not friction piles. Friction is sometimes used in the design of bored piles, but their best use is for end bearing on rock, and for applications where a lot of moment capacity is required.
As to your 50 years experience, I consider that one year, repeated 50 times. Just because you and I are old doesn't mean what we have done is correct.
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
Bored piles in these environs are friction piles; we have 50' of good clay... as for 50 years, I would suggest they have been a good 50 years, not 50x1 year... I've done just about everything except for bridges and nothing fallen down yet. Must be doing something reasonably OK and have done a lot of stuff before it was ever included in building codes... Doesn't matter much about friction or end bearing, the reinforcing stays the same and concrete is treated as plain concrete for bearing...
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik
RE: CSA A23.3 Spiral tie spacing requirements for piles
RE: CSA A23.3 Spiral tie spacing requirements for piles
Dik