Civil Engineering Reference
In-Depth Information
19.16
Using the same allowable stresses permitted and
cable stresses as in Problem 19.15, what total uniform
load, including beam weight, can the beam shown in the
accompanying illustration support for a 15-m simple
span?
c
19.15
The beam shown has a 12-m simple span:
35 MPa,
f
pu
1.725 GPa, and the initial prestress is 1.10
GPa.
(a)
Calculate the concrete stresses in the top and bottom
of the beam at midspan immediately after the tendons
are cut. (
Ans. f
top
1.766 MPa,
f
bott
12,086 (MPa)
(b)
Recalculate the stresses after assumed losses in the
tendons of 18%. (
Ans. f
top
0.618 MPa,
f
bott
9.08
MPa)
(c)
What maximum service uniform live load can the
beam support in addition to its own weight
if
allowable
stresses of
f
c
c
0.45
f
in compression and
0.5
f
in tension
are permitted? (
Ans.
10.095 kN/m)
19.17
Compute the cracking moment and the design
moment capacity of the bonded beam of Problem 19.15
if
f
py
0.8
f
pu
(
Ans.
181.68 kN
m, 438.07 kN
m)
19.18
Compute the stresses in the top and bottom of the
beam of Problem 19.14 if it is picked up at its one-third
points. Assume an impact of 100%.
c
19.19
Compute the design moment capacity of the bonded T beam shown in the accompanying illustration
f
35 MPa,
f
pu
1.725 GPa,
f
py
0.8
f
pu
and the initial stress in the cables is 1.100 GPa. (
Ans.
843.6 kN
m)
19.20
Calculate the deflection at the
L
of the beam of Problem 19.14 immediately after the cables are cut. Use I
g
.
