550
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
rat
comparison with the fix-based case, soil-pile-
structure interaction tends to increase the lateral deformation of
the structure.
ional and appropriate for further studies of the soil-pile-
structure interaction effects.
Accordingly, the maximum lateral deflection of the structure
supported by end-bearing pile foundations is increased by 17%
based on the experimental values and 19% based on the 3D
numerical predictions in comparison to the fixed base structure.
Moreover, the maximum lateral deflection of the structure
supported by shallow foundation is increased by 55% based on
the experimental values and 59% based on the 3D numerical
predictions. Thus, pile foundations reduce the lateral drifts in
comparison to the shallow foundation case. This is due to the
presence of stiff pile elements in the soft soil which increase the
stiffness of the ground and influences the dynamic properties of
the whole system such as the natural frequency and damping.
However, in
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
10
20
30
Maximum Lateral Deflection (mm)
Storey Number
Fixed base Numerical Results
Fixed base Exp. Results
Shallow foundation Numerical Results
Shallow foundation Exp. Results
End_bearing piles Numerical Results
End_bearing piles Exp. Results
Fig
n tends to
increase the inter-storey drifts of the superstructure from life
safe zone toward near collapse or even total collapse.
ure 3. Average values of maximum lateral displacements: Shaking
table experimental values versus 3D numerical predictions
The corresponding inter-storey drifts of the average values of
3D numerical model are plotted in Figure 4. Inter-storey drifts
are the most commonly used damage parameters, and based on
FEMA (BSSC 1997) maximum inter-storey drift of 1.5% is the
defined border between life safe and near collapse levels.
According to Figure 4, seismic soil-structure interactio
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
0.5
1
1.5
2
2.5
Inter-storey Drift (%)
Storey Number
Fixed base
Shallow foundation
End_bearing pile foundation
Figure 4. Average experimental inter-storey drifts for: (a) fixed-base
str
tural
period lies in the long period region of the response spectrum
acement response tends to increase.
lling method is rational and is suitable
for
raction are not adequate to
guarantee the structural safety for the moment resisting
oft soils.
Tab
Kra
Piti
olf, J.P. 1985. Dynamic soil-structure interaction. Prentice-Hall,
Englewood Cliffs, New Jersey.
ucture; (b) Structure supported by shallow foundation; (c) structure
supported by end-bearing pile foundation
The natural period of the system increases due to the soil-
structure interaction. Therefore, such increases in the natural
period considerably alter the response of the building frames
under seismic excitation. This is due to the fact that the na
curve. Hence, the displ
5 CONCLUSIONS
In this paper, a three-dimensional finite difference numerical
model on a soil-pile-structure system has been conducted
together with the experimental shaking table tests. By
comparing predicted and observed results, it has been concluded
that the numerical mode
the simulation of the soil-pile-structure interaction under
strong ground motions.
In addition, based on the shaking table results and 3D
numerical investigations it is observed that the lateral
deflections of the structures siting on the end-bearing pile
foundations amplified in comparison to the fixed base model
(approximately 18% in this study). This amplification for the
structure siting on the shallow foundations is more severe
(approximately 57% in this study). Consequently, considering
soil-structure interaction in both cases with and without pile
foundations is vital, and conventional design procedures
excluding soil-structure inte
buildings resting on s
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