Overall Conceptual Seismic Design and Local Seismic Capacity Design for Components of Bridges - Structural Seismic Design Optimization and Earthquake Engineering - page 297

Figure 25. Pile group foundation system

Table 16. Design parameters of the pile group foundation models

Model Scale Diameter

(cm)

Height
(cm)

Free
Segment
height(cm)

Pile
space(cm)

Main
reinforcement
ratio

Hoop
reinforcement
ratio

Vertical
Force at
the pier
top (kN)

1-8 1:20 9.0 72.0 49.0 44.5 0.871 0.379 75.0

Low Cycle Loading Experiments

amplitude of the cycles was variable from 2 mm
to 80 mm and the frequency of the applied signal
was equal to 0.02 Hz (Zhou, 2008).
Considering the modified Park-Ang damage
index (Park & Ang, 1985; Park, Ang, & Wen,
1985), the fiber beam element finite element
model (Figure 30) was established for these mod-
els and the low cycle loading experiments were
simulated by the finite element method.
After the experiments and finite element
analyses, the numerical and experimental hyster-
etic curves between the lateral force and the pier
top displacement are shown in Figure 31. It can
be shown that the strength of the models strength-
ened with SPPs is about 1.77 times and the ultimate
displacement is about 1.66 times of the ones of
the RC models. Additionally, the hysteretic en-
ergy dissipation capabilities of the models
strengthened with SPPs are more than 2.15 times
of the RC models, while the equivalent viscous

From the above analyses results, it can be con-
cluded that the pile group foundation strengthened
with SPPs has better seismic capacities than the
foundation without the SPP. So it is necessary to
further study the energy dissipation and hyster-
etic performance under earthquakes in order to
promote the application of the pile group foun-
dation strengthened with SPPs. Then another
four scale-models, Model 5 to 8, are established,
whose design parameters are listed in Table 16
too. Model 5 and 6 are normal reinforced concrete
(RC) pile group foundations and Model 7 and 8
are foundations strengthened with SPPs, whose
pipe wall thickness is 0.1cm and length is 40cm
beginning from the pile top. Moreover, the low
cycle loading experiments (Figure 29) were con-
ducted for these models in the electro-hydraulic
servo loading system in Tongji University. The