Structural Concrete - Hassoun

916 Chapter 22 Prestressed Concrete Bridge Design
BRIDGE DESIGN EXAMPLE
The design example is intended to provide guidance on the application of the AASHTO LRFD
Bridge Design Specifications when applied to a very common type of composite deck superstructure.
Design the simply supported pretension prestressed concrete girder bridge of Fig. 22.12 with a span
length of 100 ft center-to-center bearings of an HL-93 live load.
34’–10”
1’–5”
4’–0” 12’–0”
12’–0”
4’–0” 1’–5”
Shoulder
Shoulder
Concrete barrier
732, Typ
PG
– 2% – 2%
8”
2’–8”
Typ
6”
Typ
¾” Drip
groove, Typ
1’ Min
See Note
6’–0”
Min
8”
Typ
AASHTO – PCI
BT – 63, Typ
C L Girder,
Typ
C L Bridge
3 spacings @ 9’–0” = 27’–0”
Note:
1” minimum hounch at C L abuntment bearing and varies along profile to allow for camber.
3’–11”
Typ
Figure 22.12 Prestress concrete girder bridge design example: cross section of bridge
with AASHTO-PCI bulb tee (BT-63).
The roadway width is 32 ft curb to curb. The bridge is to carry interstate traffic over a highway
with minimum clearance of 16 ′ −6 ′′ .
Follow AASHTO LRFD Bridge Design Specification, 7th edition [1].
BRIDGE GEOMETRY DATA GIVEN
w = 28 ft
L = 100 ft
w bridge = 34.83 ft
w barrier-bottom = 1.417 ft
h barrier-top = 1 ft
h barrier = 2.67 ft
t oh_ext = 8 in.
t oh_ext = 12.5 in.
L oh = 2.17 ft
o g = 4
n b = 2
Roadway width
Bridge span length
Bridge width = bridge width +2(barrier)
Bottom of concrete barrier width
Top of concrete barrier width
Height of barrier
Exterior overhang thickness
Interior overhang thickness
Length of overhang
Number of girder
Number of barrier