endons in 2 way slabs - flat bundles only

huangyhg

tendons in 2 way slabs - flat bundles only?
just a quick question, is it absolutely required to have flat bundles in a pt 2 way slab?  or can you have stacked bundles to ease congestion over a column (such as two on top and two beneath).  this would be in a 12" thick slab.
thanks,
don't understand your terminology.  what is a "flat bundle"?  usual practice is to use ducts which are about 70mm wide x 19 mm deep, and you can fit 4 or 5 strands in each duct.  so why would you want to have two layers in the same direction?  
do you mean laying out the tendons side-by-side to maximize the cgs? if the strands are all stacked together then it could be a cgs change from anticipated.
it will be hard enough to get the tendons high enough at the column anyway.  stacking them on top of each other won't make that any easier.
i know the column is very congested, but placing tendons in layers reduced your eccentricity and hence, load balance. i think the fact that you are using cables lower than their usual high points at columns should be accounted for.
also, during the ultimate time, the tendons near the top will contribute very less in the moment carrying capacity. more over, to maintain a minimum amount of precompression, you will have to increase the number of tendons. this will happen due to the reduced eccentricity of the tendons.