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Real-time dynamic hybrid testingfor soil-structure interaction analysis
Wang Qiang & Zhang Chuhan
2009-10-15
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CONTENTS
2
3
4
5
Introduction of soil-structure interaction
RTDHT system in Tsinghua University
Soil-structure interaction model
SSI-RTDHT test setup
SSI-RTDHT test results
1
6 CONCLUSION
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Soil and structure should be considered as a whole system in dynamic analysis.
Introduction of soil-structure interaction1
Direct method Substructure method
the structure and the soil are treatedas two different substructures.
Each substructure can be analyzedusing a best-suited computational
technique.
Combining the force-displacementrelationship of the soil with the
discretized motion equation of the
structure, results in the final systemof equation of the total dynamic
system.
the structure and soil are treatedas a whole system.
The region of the soil adjacent tothe structure-soil interface is also
explicitly modeled.
Artificial boundary must beintroduced so as to cover the
unbounded soil domain.
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Considering SSI in shaking-table tests is still a problematic option.
Introduction of soil-structure interaction1
Model box with finite region of soil Model boundary with damping material
(Chen, et al. 2005) (Li, et al. 2003)
Shaking
table
Finite
region ofSoil
structure
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Combining the numerical calculations of semi-infinite soil together withsuperstructure large scale model testing.
Introduction of soil-structure interaction1
RTDHT
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RTDHT system in Tsinghua University2
Distributed real-time calculation system
Host PC Ordinarycomputer with
Windowsoperating system
Target PC Ordinarycomputer without
Windows operatingsystem (but xPC
kernel)
Software Matlab,Simulink,
Real-time workshop,xPC target
Shared common RAM network
high-speed:16.7 Mb/s
ultra-low-latency:250 ns
SCRAMNet cardSC150
Optical cableShaking table loading system
Area:1.5m 1.5 m
Bearing capacity:2 t
Max acceleration:3.6 g (bare table)1.2 g (full loaded)
Frequency:0~50 Hz
MTS 469D controller:Mathworks Simulink is integratedinto the controller platform
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Soil-structure interaction model3
Lumped parameter model used in this paper
Luan Maotian & Lin Gao 1996
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Soil-structure interaction model3
Lumped parameter model used in this paper
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Soil-structure interaction model3
If the system is excited by harmonic force, the external force and displacement vector can be rewritten as follows:
Dynamic stiffness coefficient
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Soil-structure interaction model3
Dynamic stiffness coefficient
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SSI-RTDHT test setup4
Motion equation
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SSI-RTDHT test setup4
Concretize2
Soil properties: Mass denscity
Soft Soil: Hard Soil:
Cfe=3.016107 Ns/m
Kfe=2.513108 N/m
Mfe=3.619106 kg
Kfe=4.021109 N/m
Cfe=1.2064108 Ns/m
Mfe=3.619106 kg
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SSI-RTDHT test setup4
Substructuring3
1
2
Physical substructure
Numerical substructure
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SSI-RTDHT test setup4
Model and measurements4
AccelerometerFor accelerationmeasurement
Strain gauges bridgeFor shear forcemeasurement
LVDTFor displacementmeasurement
NI DAQFor data acquisition
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SSI-RTDHT test setup4
Procedure of SSI-RTDHT5
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SSI-RTDHT test results5
The mesh boundary is far enough so that the effect of the wave reflection and scattering from boundary on
the structure-soil interface response can be avoided during the calculation duration.
1. Far boundary FEM
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SSI-RTDHT test results5
2. Artificial wave
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SSI-RTDHT test results5
3. Accuracy verification of lumped paremeter model
Peak comparison
LPM: 1.226 gFEM: 1.147 g.
Error: 6.9 %
Peak comparison
LPM: 0.793 gFEM: 0.773 g
Error: 2.6 %
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SSI-RTDHT test results5
3. Accuracy verification of lumped paremeter model
Peak comparison
LPM: 9.751 mmFEM: 9.594 mm
Error: 1.6 %
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SSI-RTDHT test results5
3. Accuracy verification of lumped paremeter model
Peak comparison
LPM: 635.1kNFEM: 597.3 kN
Error: 6.33 %
Peak comparison
LPM: 688.7kNFEM: 689.6 kN
Error: 0.13 %
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SSI-RTDHT test results5
4. Accuracy verification of SSI-RTDHT
Peak comparison
SSI-RTDHT: 1.317 gFEM: 1.147 g
Error: 14.8 %
Peak comparison
SSI-RTDHT: 1.179 gFEM: 0.773 g
Error: 52.5 %
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SSI-RTDHT test results5
4. Accuracy verification of SSI-RTDHT
Peak comparison
SSI-RTDHT: 10.39 mmFEM: 9.594 mm
Error: 8.3 %
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SSI-RTDHT test results5
4. Accuracy verification of SSI-RTDHT
Peak comparison
SSI-RTDHT: 659.7 kNFEM: 597.3 kN
Error: 10.4 %
Peak comparison
SSI-RTDHT: 728.2 kNFEM: 689.6 kN
Error: 5.6 %
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SSI-RTDHT test results5
5. SSI effect of different types of soil
Peak comparison
SOFT 0.40 gRIGID 0.55 g
REDUCT: 27.3 %
Peak comparison
SOFT 0.35 gRIGID 0.27 g
REDUCT: 22.9 %
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SSI-RTDHT test results5
5. SSI effect of different types of soil
Peak comparison
SOFT 245 kNRIGID 399 kN
REDUCT: 38.6 %
Peak comparison
SOFT 196 kNRIGID 260 kN
REDUCT: 24.6 %
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CONCLUSION6
1. The lumped parameter model used in this paper can give a high accuracyapproximation of the infinite half space elastic foundation.
2. Comparing the SSI-RTDHT test results with the FEM results shows that SSI
-RTDHT can produce satisfying results in SSI analysis.3. Comparing the tests results under rigid foundation, hard soil foundation, and
soft soil foundation show that soil-structure interaction can affect the response of
the structure: softer the soil is, more obvious the SSI effect becomes.
Using the idea of RTDHT, the infinite soil foundation model calculation and
superstructure testing are combined together. Radiation damping of the infinitefoundation can be included in shaking-table tests.
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THE END
CONCLUSION