Post Tensioned Floor Slabs

[hannis]

I'm currently carrying out a code compliance check of a multistorey building that has 9" PT floor slabs. Unfortunately I only have an academic understanding of PT slabs. Are there practical issues in terms of the drawing design details etc that I should be aware of. I have already read with interest Y3392 problems with hairline cracking on a former thread.

Many thanks

Hannis

 

[AUCE98]

Hannis,

I would recommend looking at “Design Fundamentals of Post-Tensioned Concrete Floors” published by PTI. It has a wealth of information on design practice and detailing which may be helpful in you quest. It was written by Bijan O. Aalami, an authority on PT design.

Regards,

AUCE98

 

[lutein]

Hannis was right on the point -
other than reading "Design Fundamentals of Post-Tensioned Concrete Floors"
you could also look at "Design, Construction and Maintanance of Cast-In-Place Post-Tensioned Concrete PArking Structures"

Some tips -
1. Always check the deflection of Selfweight+PT combo, to ensure you do not get excessive camber.
2. Dont over post tension your slab. But, at the same time, also try to minimize use of bottom mild reinforcement (conventional rebar) by increasing the tendons profile or increase number of tendons.
3. Always show required anchorage reinforcement, if not shown, at least call out or mention to refer to PT supplier's dwgs. they are very important.
4. Check tendon spacing at middle and at anchorage. Sometimes, you may end up putting the number of tendons that is not constructable simply because you dont have anough space for anchorage.
5. If you are using comp. software, like ADAPT or FLOOR to do your design, aways check your model with the real situation, i.e. boundary conditions, extension of columns, walls, anchorage height,etc.

 

[hannis]

Lutein/AUCE98

Thanks very much, the advice and tips are helpful.

Regards

Colin