Civil Engineering Reference
In-Depth Information
19.9
Compute the design moment capacity of the preten-
sioned beam of Problem 19.2 if
5000 psi,
f
py
200,000 psi, and
f
pu
225 ksi. Assume
19.8
Calculate the design moment capacity of a 12-in.
20-in. pretensioned beam that is prestressed with 1.2 in.
2
of steel tendons stressed to an initial stress of 160 ksi. The
center of gravity of the tendons is 3 in. above the bottom
of the beam;
c
f
f
py
f
pu
0.85. (
Ans.
293.1 ft-k)
c
f
5000 psi,
f
py
200,000 psi, and
f
pu
250,000 psi.
c
19.10
Compute the design moment capacity of the bonded T beam shown in the accompanying illustration if
f
5000
psi,
f
pu
250,000 psi, and the initial stress in the cables is 160,000 psi. Also
f
py
200,000 psi.
19.11
Calculate the deflection at the
L
of the beam in
Problem 19.3 immediately after the cables are cut, assum-
ing cable stress
160,000 psi. (
Ans.
0.225 in.
a
)
ing
P
initial
240 k and
P
after losses
190 k. Repeat
the calculation after losses if 20-k concentrated live loads
are located at the one-third points of the beam and
5000 psi. Assume that cables are straight and that no loads
are present other than the beam weight and the two 20-k
loads. Use
I
g
for all calculations.
c
f
19.12
Calculate the deflection at the
L
of the beam in
Problem 19.1 immediately after the cables are cut, assum-
