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AASHTO Precast Ratings

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I am using the 1996 AASHTO Manual for Condition Rating of Bridges to rate a precast hollow core slab unit.  In Section 6.6.3.3 there are two RF formulas involving fy*.  Fy* for the strands in question is around 211 ksi.  When determining the Fd, Fp, Fs, and Fl stresses for these two equations, aren’t these the section stresses which are typically very small in comparison with fy*?  If the Fd, Fp… are to be the stresses in the prestress strands due to applied loads, I am confused about how to determine them when the section is supposedly uncracked. 

 

Please supply some direction on how to calculate these RF and/or an explanation of these formulas.

 

Rob Schnelle, P.E., S.E.

Zurheide-Herrmann

P: 217.352.1435

F: 217.352.1458

E: RSchnelle(--nospam--at)ZHideas.com