a Flexure: for factory-produced precast prestressed concrete members, f = 1.0. For posttensioned cast-in-place concrete members, f = 0.95 by AASHTO. b Shear and Torsion: Reduction factor for prestressed members, f = 0.90 by AASHTO.

PHOTO 8.5 Walt Disney World Monorail, Orlando, Florida: a series of hollow prestressed concrete 100-ft box girders individually posttensioned to provide a six-span continuous structure. Design by ABAM Engineers and owned by Walt Disney World Company (courtesy E.G. Nawy).

8.6.7 Limit States in Bonded Members from Decompression to Ultimate Load

The effective prestress fpe at service load due to all loads results in a strain e1 such that

f ps

At decompression, that is, when the compressive stress in the surrounding concrete at the level of the prestressing tendon is neutralized by the tensile stress due to overload, a decompression strain £decomp = e2 results such that

(a) Compression side

0 0

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