Curved concrete bridges - Computational Analysis and Design of Bridge Structures - page 182

In the case of a multilane bridge, a multilane presence factor should be
included.
6.2.4 Modeling of lateral restraint and movement
Bearings in a horizontal curved bridge may be restraint in lateral to prevent
movement due to the centrifugal forces from traffic load, thermal move-
ment, and prestress shortening. The bearing should be so modeled to reflect
its actual movement and restraints in all directions.
6.3 sPine Model illustrated exaMPles
of PengPo interChange, henan,
PeoPle's rePuBliC of China
This illustrated example is a ramp bridge located in Pengpo Interchange, one of
the major transportation hubs in Henan, China. It has a total length of 343.465 m,
with a radius of 130 m for the first 150 m, a left transition curve for the next
50 m, and a radius of 400 m for the rest of the ramp bridge. The bridge is shown
in Figure 6.9. The bridge is designed as cast-in-place prestressed concrete con-
tinuous box girder bridge, with a bridge roadway width of 7.5 m + 2 × 0.5 m.
The span layout of this bridge contains two 6 continuous spans with the first
one 6 × 30 m and the second one 6 × 25.88 m (Figure 6.9). Typical cross section
of the bridge is shown in Figure 6.10. The bridge uses elastomeric bearing pads
with various sizes ranging from 500 × 87 mm 2 to 900 × 115 mm 2 .
The purpose of this analysis is to find the reason of damage to bearings
and substructure pier columns due to lateral movement. Pengpo Bridge sup-
port arrangement plan is shown in Figure 6.11a, and its movement sketch is
shown in Figure 6.11b. During the inspection, it was found that though the
bridge superstructure's performance meets the original design requirement,
large shear deformation and transversal displacement occurred through-
out the bearings in the ramp bridge, ranging from 10 mm at bearing #0 to
90 mm at bearing #6.
To understand the cause of the damage, a 3D model of the first 150-m ramp
bridge was generated by CSIBridge, as shown in Figure 6.12. The elastomeric
bearing pads were modeled by introducing the stiffness values in vertical,
horizontal, and lateral directions provided by bearing pads. A lateral load
of moving vehicle centrifugal force was introduced following the AASHTO
instructions, which is triggered by 20 tons of vehicles traveling at about 60
km/hour. The deflection is shown in Figure 6.13. The CSIBridge model results
show that displacements among the supports are different from 7.25 mm at
bearing #0 to 56.3 mm at bearing #6, which is reasonably close to the field-
inspection results. It is detected from the results that the centrifugal force
from traffic may be the main reason that this example bridge got damaged.