circular tie details for drilled piers

huangyhg

circular tie details for drilled piers
i have two concerns about the circular ties (#6) for my drilled piers (for river embankment stabilization, under mostly large bending and shear, minimum axial, 36"dia, 24#11 with #6 ties @ 3"-4" spa)
1. the lap length - is 48 db sufficient (36" as lap length)?
2. the lap details - should the lap steel be overlaping with the circular tie or turning into the interior of the cross section(seems to be preferred by fhwa)?  if the lap is 48db (36") there is barely enough room for the lap.  what about the constructibility?
thanks for the help!  
use spiral ties.
ols ca se
is there a reason you need #6 ties?  usually #3 or #4 are used.  
also, if the member is taking mostly bending and shear, it's classified as a tension controlled   
shear (500 kips factored)is too high for spirals - size of spirals are limited to #5 unless you go with special heavy equipment.  i can not size up the shaft either.  it seems the only option is #6 ties.
if the direction of the shear can be predicted, can you use smaller ties and add #6 or #7's spanning across the interior of the piers (parallel to the load direction)?  they'll be tough to install, but there should be room to get the mud in.
also increase f'c?

fc'is 4000psi.  anything above that will have special requirement by aci318.
these shafts are one of the many sections of shafts along the river emankment.  the clients wanted use same diameter shafts (36") and similar details....same strength of concrete...therefore to cut their cost. they claimed that #6 ties have been used in another section. although #6 circular ties may be out of the ordinary but will it be a solution?  i am mostly interested in the details of it......
thanks!
khkw
i'd use #4 circular ties but then add rectangular #5 or #6 per jedclampett's suggestion above if the load is of a known direction.  you could create a rectangular rebar cage within the circular cage to fit together - and perhaps do this only in the top portions of the pier.  
getting the concrete down the shaft might be an issue (as jed suggested above).  one thought would be to fill the pier up to a point and then drop in an internal rectangular cage, tie it off to the cirular cage and then continue with the concrete placement.
but tying it all together at the start is preferred.

i would stick with the circular #6 ties if you can't get #6 made into a spiral.  but as for the laps, that is not the way to go.  you should be able to bend the ends of the ties 135 degrees around alternate bars; that is, one vertical bar space between the bends.  just check with a reinforcing supplier in your area about bending these ties, but i have seen it done where i am.
thanks for all your responses!  jedclampett and jae both have very good points.  but i think introducing #6 or #7's spanning across the interior of the piers might jack up the cost more than they wanted.  hokie66's idea is refreshing but how do you achieve the splice length (36") with 135 degree between bends. also by doing this it will create honey cones in the space between the splice and the ties - an issue for concrete to get thru......
perhaps my post was confusing.  the ties are made continuous by 135 degree hooks at each end rather than by splice length.  these hooks are not around the same vertical bar, but rather around alternate bars, which allows space for the vertical bars and avoids the type of congestion that may cause honeycombing.  also, the location of the tie terminations should be varied around the perimeter of the pier.