Prestressed/post-tensioned concrete bridges - Computational Analysis and Design of Bridge Structures - page 160

Figure 5.36 Displacements in the beam due to structural weight and prestressing,
US23043 Bridge model 1.
5.5.2 us23043 bridge analysis results
5.5.2.1 Model 1: Slab modeled with beam elements
Model 1 will show the results of creep and shrinkage effects on bridge
US23043. This model will provide the moments and longitudinal forces
of the plate, beam, and prestressing tendon. The cast-in-place slab is stress
free after hardening if no additional loads are applied, whereas the pre-
stressed beam elements carry the structural weight.
The elastic displacements shown in Figure 5.36 reach 13 mm (0.5″) in
one region. The displacements after five years are 148 mm (5.8″) consider-
ing creep and shrinkage with CEB-FIP and 64 mm (2.5″) with AASHTO
specifications. Figure 5.37 shows the displacements due to creep and shrink-
age and the total displacements after five years for both codes. Included in
these results are the creep displacements that took place between the time
the beams were precast and placed. These calculations, of course, depend
upon how the beams were supported in this period of time. In this model,
the structural weight is applied once the beam is placed at the site.
5.6 illustrated exaMPle of a three-sPan
Prestressed Box-girder Bridge
A three-span single-cell haunched prestressed box girder bridge (Ketchum and
Scordelis 1986) is taken as an illustrated example in this section. Figure 5.38
shows its elevation profile, and Figure 5.39 shows its cross-sectional geometry.