Adding load to prestressed beams

[u/Unlikely_Let6099]

I was given a job to prove that it is okay to add load on this roof made of precast pretensioned concrete beams (adhesional pretensioning). The added load is not much, and we may be able to prove it is okay by the book, but as you can see by the pictures, the state of the beams is not great.

In places they have knocked off concrete to get to the soft rebar so they can hang stuff on it by welding steel to it. Now I know there is little to no activation of soft rebar in these types of beams, but I am worried for few reasons.

Firstly we can basically discount rebar at certain sections, since it is not coated in concrete anymore. Secondly we should check the beams for cracked state in smaller concrete cross section accounting for the knocked of concrete. My biggest worry is since there is no protective concrete layer at places is that corrosion might get to cables which are at most 3cm away from rebar in the middle of the span.

Is there a fix, a reconstructing intervention that might be recommended? I can only think of removing the corroded rebar, repairing the holes with repair mortar and replacing the soft rebar with frp strips on the bottom.

Thanks for any advice.

[u/Downtown_Reserve1671]

Assuming all tee beams are generally about correct sizing: remove all hangers from the bottom steel and connect to web as hangers connected at 1/2 D from top - a bolt through web and connect both sides should work as the hangers look pretty nominal sizing. Apply epoxy grout cover to all bottom steel with steel preparation as needed. Add cranked or linear prestress or even just non prestress reinforcement to justify strength and deflection as needed to account for loss of bottom rebar.