Post-Tensioned Slab


One of the major design challenges when we design a Post-Tensioned transfer slab, is to consider the sequence of construction, so it’s required to stress the tendons in stages until reaching its final force.

The question here, which approach is more reliable and can be considered in compatibility with the effective force equation considering friction losses?

1- stressing all the cables for example to 50% of the total force.


2- stressing cables in T1 and T3 to 100% of the force and keep cables in T2 unstressed until later stages.

Here we have two concerns:

1- can we consider a linear relationship between the remaining jacking force and the friction losses? Ex: If I stress 50% of the total force, 50% of the friction losses take place, is it correct to say that if I stress the remaining 50% the resting 50% friction losses will take place with no increase?

2- Strut and tie method should be used to calculate the required reinforcement ( highlighted in red) needed to resist the tension force present due to the prestressing force and check whether the provided mesh reinforcement can take care of this induced tension force.

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