Post tensioned slab - tendon coupler

[dadomago75]

Hi All,
I looked everywhere but I couldn't find any specific information, and when I found some info they were kind of contracting each other (or maybe it would be better to say that they did not agree).

1 - do couplers always have to be at slab mid depth? (I don't think so).
2 - do couplers need anti-bursting reinforcement? (I don't think they always need. I think anti-bursting reo is required only when the first pour is stressed before setting the second pour. If a coupler is connected and the tendons are stressed at each end at the same time there should be no need of anti-bursting reo).

thanks
Davide

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[Ingenuity]

Bonded (grouted) or UNbonded PT system?

I think you are talking about a bonded system (monostrands), so the following is based upon such:

1. For a slab - assuming 'normal' proportions (say 6" through 10" thick) - it is most usual to have couplers at mid-depth of slab.

2. At intermediate stressing locations, anchorage reinforcement is required only on the intermediate CJ location where the anchorage is embedded/cast and stressed, and such reinforcement theoretically becomes redundant after full tendon length has been stressed at the far end.
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Depending how your detail the couplers, it is common for BONDED systems in slabs to have bare strand exposed for a few feet (500mm) as the tendons fan-out from the couplers/anchorage to the ducting. Such a detail prohibits the intermediate anchorage/s from being fully 'unloaded' after the far end of the slab tendons have been stressed.