fpo

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gnava
fpo

I see that PGSuper uses .7fpu for fpo in calculating shear capacity. Is there a way to adjust this value to .75fpu as mentioned in AASHTO 5.8.3.4.2 commentary for pretensioned members? It makes a fair difference in calculating theta. I wouldn't really bother for a new design, but I am rating an existing structure.

Rick Brice
fpo

There is not a way to adjust fpo. It is hard coded as 0.7fpu.

I will put an item on our to-do list to compute fpo according to C5.8.3.4.2.

Rick

Richard Brice, PE
Software Application Engineer
WSDOT Bridge and Structures Office

Pickings
fpo

Quoting the commentary: "For pretensioned members, fpo can be taken as the stress in the strands when the concrete is cast around them, i.e., approximately equal to the jacking stress."
PGSuper allows direct input of the jacking force on the Girder Editor - Strands tab. However, this actual jacking stress is not used when computing strain (5.8.3.4.2-4). It seems to me that this might be the problem.
So the question: Would it be better to carry this actual jacking stress into the equation, or provide new input for a parametric factor on Fpu (e.g., 0.7) in the Project Critieria library?

Richard Pickings, P.E.
BridgeSight Inc.

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