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reinforcement forces fall between the active and at-rest bounds in the upper two
thirds (6.5m) of the wall. In the lower third of the wall, however, the maximum
reinforcement forces fall below the lower bound. Although not a focus of the
present study, it is beneficial to explain this behavior. Design guidelines are based
on idea that the horizontal pressures within a certain tributary area are carried by
the corresponding reinforcements. Assumed horizontal stresses are based on
simple earth pressure theories that assume rigid-plastic behavior. The actual
stress deformation pattern within the wall, however, is different and more
complicated. Also, sharing of stresses among the reinforcements is more
complicated than is assumed by the simple tributary area concept. Lower sections
of the wall do not have the same mobility to deform as the upper portions of the
wall. These differences result in a decrease in the forces taken by the lower
elevation reinforcements, and an increase in the reinforcements in the upper
levels (relative to the design values). Other factors that affect the maximum
reinforcement forces include the connection of the reinforcement to the facing
panel, relative movement between the facing panel and the backfill soil, and
passive pressures due to soil retained on the outside of the wall. For instance, the
approximate 1 m of wall embedment (see bottom portion of wall in
Fig. 3)
resulted in a further decrease of reinforcement forces near the bottom of the wall.
6 DYNAMIC ANALYSIS AND RESULTS
A dynamic analysis that stimulated earthquake shaking was carried out following
the static analysis. Stiffness of the backfill and the foundation soil were calculated
from the end-of-construction stress states based on the above-mentioned
relationships. Likewise, the shear strength of the backfill and foundation soil
followed the Mohr-Coulomb criteria described above. For these dynamic
analyses, deformations are assumed linear-elastic below yielding, and plastic
flow is assumed at the yielding stress.
The east-west component of the acceleration time history recorded at the
YPT (Yarimca, Petkim) Station during the Kocaeli earthquake was used in the
analysis. The YPT Station is about 40 km from the Airfiye site and located on
ground conditions similar to those at Arifiye. The acceleration record was
baseline-corrected, and frequencies above 15 Hz were removed by low-pass
filtering. This processing was needed to ensure that the input motion can be
transmitted within the finite-difference grid without being distorted (Kuhlemeyer
and Lysmer, 1973). An additional filtering process was performed to attain a zero
displacement at the end of the record (these corrections are necessary to minimize
errors for displacement-based numerical methods). Acceleration and velocity
time histories of the record after filtering are shown in
Fig. 7.
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