Prestressed Concrete fps vs fse

What is the difference between fps and fse?

fps: stress in prestressed reinforcement at nominal strength

fse: effective stress in prestressed reinforcement after allowance for all prestress losses

My interpretation, which I'm not sure is correct:

fse is an upper bound to fps. Fps = fse when the prestressed reinforcement is the limiting factor. fps can be lower than fse if the concrete crushes first.

edit: now I understand. My misunderstnading was I thought that fse was a stress after external loads are applied.

fse = the effective stressed in the prestressed reinforcement, after prestressing and losses but before external loads. fps is the stress after external loads are applied.

fps: by Arthur Nilson, Design of Prestressed Concrete, "the steel stress when the beam fails. It may be equal to fpu, but is usually somewhat below it depending on the geometry of the beam, steel ratio, material properties and initial prestress in steel." 

fpe:  by ACI, compressive stress in concrete due only to effective prestress forces, after allowance for all prestress losses, at extreme fiber of section if tensile stress is caused by externally applied loads. 

fps: by ACI, stress in prestressing reinforcement at nominal flexural strength. 

very helpful, thank you.

I was getting a little confussed with all of the fs!

Thank you for the useful information.

Ok, i get you guys...

The fittings in the products can be non-stressed and strained. The first type performs the function of passive reinforcement — it does not work until the plate bends from its weight or the impact of a transverse load.
Only at this moment will the lower reinforcing rods resist stretching, but the concrete will already receive its share of stretching and react with a network of small cracks.
I learned all this while remodeling the staircase entrance to the house. Since ice and snow can make it difficult to step on, I added a few elements that would allow you to climb the steps even in winter safely.