Redundancy analysis - Computational Analysis and Design of Bridge Structures - page 477

L Beam

L Beam

1′ 4″

2 1/2″ 2 1/2″

2″ 2″ 2″

Typ.

#4

2 - #4
Continuous

4 1/2″

#5

1″Cl.

1″Cl.

#4

7″

7 1/2″

#4

#4

2 Spa. @ 2″

2″

2″ 9 Spa. @ 2″ 2″ Dimensions and reinf.

same as section A-A
except as shown.

1′ 10″

(a) Section A-A (b) Section B-B

Type III Beam
Scale: 1″ = 1′-0′

Figure 15.8 (a, b) AASHTO type III beam cross sections.

dimensions and prestressing tendon layout are shown in Figure 15.8.
Section A-A corresponds to the end of the bridge, while Section B-B is the
beam cross section at the bridge midspan. The prestressed beam concrete
has a minimum 28-day compressive strength of 5000 psi (34.5 MPa) and a
minimum compressive strength of 4000 psi (27.6 MPa) when jacking. The
prestressing tendons are number 7 wire strand, with 1/2″ (13 mm) diameter
and a cross-sectional area of 0.153 in 2 (98.7 mm 2 ). The capacity of the wire
is 270 ksi (1861.7 MPa).

15.4.1 Bridge model
SAP2000 (2007) is used to create a model of the prestressed concrete beam
bridge. As this example is concerned with the response of the deck as well
as the beams, the deck is also modeled using frame elements. By defin-
ing the deck as frame elements, nonlinear hinges (or plastic hinges) can
be assigned, so the deck will exhibit nonlinear plastic behavior. To prop-
erly model the bridge deck and account for transverse and longitudinal
stiffness, a grid of frame elements is created. The deck frame elements are