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 (14) Check maximum reinforcement.
ppfps/f'dc = .000290 x 268,167/6250
= 0.0124
0.36K1 = 0.36 x 0.7375
= 0.2655
0.0124 < /= 0.2655
O.K.
(15) Design for rebound.
Reinforcing steel bars are now the
main reinforcement.
From Figure 6-8 of NAVFAC P-397
r -/ru = 1.0
Required negative resistance
r -req = r - - DL >/= ravail/2
= 70.9 - 43.1
= 27.8 lb/in
ravail/2 = 70.9/2
= 35.5 lb/in
27.8 < 35.5, therefore use 35.5 lb/in
Considering a single tee
r -req = 35.5/2
= 17.7 lb/in
d - = 25 - 0.625 - 0.135 - 0.375 -0.5/2
= 23.62 in
M -u = r -L2/8
= 17.7(40 x 12)2/8
= 509,760 in-lb
Concrete capacity available after accounting for
prestressing effects:
0.49f -dc = 0.49(6250)
= 3062.5 psi
Assume a = 2.0 in
A -s = M -u/[fdy(d - - a/2)]
= 509,760/[66,000(23.62 - 1.0)]
= 0.341 in2
2.08-263
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