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 If any compression reinforcement is taken into account when calculating
fps then the distance from the extreme compression fiber to be centroid of
the compression reinforcement must be less than 0.15dp and
[ppfpu/f'dc + (fdy/dpf'dc) (p-p')] >/= 0.17
If there is no compression reinforcement and no non-prestressed tension
reinforcement, Equation (145) becomes:
EQUATION;
fps = fpu [1- ([UPSILON]p/K1)pp (fpu/f'dc)]
(146)
For members with unbonded prestressing tendons and a span-to-depth ratio
less than or equal to 35:
EQUATIONS:
fps = fse + 10,000 + f'dc/(100pp) < /= fpy
(147a)
and
fps < /= fse + 60,000
(147b)
where,
fse = effective stress in prestressed reinforcement after
allowances for all prestress losses, psi
For members with unbonded prestressing tendons and a span-to-depth ratio
greater than 35:
EQUATIONS:
fps = fse + 10,000 + f'dc/(300 pp) < /= fpy
(148a)
and
fps < /= fse + 30,000
(148b)
(b) To insure against sudden compression failure the reinforcement
ratios for a rectangular beam, or for a flanged section where the thickness
of the compression flange is greater than or equal to the depth of the
equivalent rectangular stress block will be such that:
EQUATION:
ppfps/f'dc + (dfdy/dpf'dc)(p-p') < /= 0.36K1
(149)
When the thickness of the compression flange of a flanged section is less
than the depth of the equivalent retangular stress block, the reinforcement
ratios will be such that:
2.08-222
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