Distributed tendon layout

[strguy11]

I had posted this in the pt forum but had no responses...

I have a couple of questions regarding how to show the layout of Distributed tendons in my 2-way slab.

1. How many strands can be "bundled" for the distributed together. I have read (4) but i have seen drawings that show 5 strands at a 5'-0" oc spacing. I am thinking 5 would be the max.

2. Are most people showing all of the tendons across the slab, or say only showing (1) within an area and just giving an effective force per foot of this area of similar tendons?

3. I have an area where i laid out most of the tendons at a 5' o.c. spacing, and for the most part, 5 tendons at 5 feet on center work for the distributed tendons. I do have one area that based on the span, i need to increase some of these to like 8 tendons at 5' on center. Is it ok just to show these as 8 tendons at 5' o.c. or should i show them as (4) tendons at 2'-6" o.c. or just show the effective force per linear foot? What are most people doing?

4. Is there a maximum precompression limit? I have never seen one posted, but i have read that for a podium type of structure 300 to 350 psi seems to be practical. More than that a thicker slab might need to be considered. Correct?

My thought is to just use the layout i got to work in my software (ADAPT) (the 8 tendons at 5' o.c as described aobve) and have the PT supplier show the layout that works for them. What is everyone doing?

 

[dik]

Does this thread help? An excellent set of drawings that shows the GA.

thread507-425138

Dik

 

[KootK]

Are most people showing all of the tendons across the slab, or say only showing (1) within an area and just giving an effective force per foot of this area of similar tendons?

I typically see it done on a kip/ft basis just as you're suggesting.

how many strands can be "bundled" for the distributed together.

This article recommends a maximum of four strands bundled on order to discourage delamination and blowout issues.

Is there a maximum precompression limit? I have never seen one posted, but i have read that for a podium type of structure 300 to 350 psi seems to be practical. More than that a thicker slab might need to be considered. Correct?

About that. I've heard things like:

1) Slabs 250 - 300 psi
2) Transfer plate 300 - 350 psi
3) Beams 350 - 400 psi.

I believe that the limits are largely to do with economy and restraint effects. If careful consideration if given to restraint effects, I believe that you can go a good deal higher than these numbers wrt precoompression.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.