Post Tensioned No P/A

[chillerz69]

I am currently setting up a spreadsheet to calculate strengths, stresses etc of prestressed beams and slabs. I have been instructed to have the option of whether or not to include the P/A component, as sometimes axial deformation cannot occur when the slab is say tied into stiff walls or frames. How should I modify my limit state strength equations and stress equations to allow for this? Anyone know where I can look this up?
Cheers

 

[civilperson]

I can not envision any conditions for post tensioned beam/slab that is restrained enough to prevent elastic shortening of the concrete due to steel stress.

 

[kozidran]

If your axial deformation is limited, then just design the beam as normal RC beam with uplift from tendons. It's conservative but it's safe.
Check that supports can withstand the axial deformation as it will occur anyway (add the tendon forces to get reaction estimation).
The safest way is to put a temporary strip and forget about the defomation.