Earthquake Design of Retaining Structures Master thesis Dansk Geoteknisk Forening, Aarhus Earthquake...
Transcript of Earthquake Design of Retaining Structures Master thesis Dansk Geoteknisk Forening, Aarhus Earthquake...
Earthquake Design of Retaining StructuresMaster thesis
Antonela-Flavia Achimp
Supervisor: Varvara Zania, Technical University of Denmark
External supervisors: Andrija Krivokapic, Rambøll
Carsten Lyse, Cowi
22/10/2015Earthquake Design of Retaining Structures2 Dansk Geoteknisk Forening, Aarhus
Contents
Introduction
• Problem Statement
• Motivation of the Study
• Investigation Strategy
Literature
• Pseudostatic Analysis
• Dynamic Analysis
• Westergaard Solution
• Eurocode EN 1998-5
Numerical Modelling
• Westergaard Solution
• L-Shaped Retaining Wall
Case Study
• Pseudostatic Analysis
• Dynamic Analysis
Conclusions and Further Research
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Problem Statement
Introduction-Problem Statement
Water Backfill + WaterWall
Static forces Dynamic forces
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Motivation of the Study
Introduction-Motivation of the Study
• Pseudostatic
• Full-Dynamic
When taking a decision:-resources: seismic hazard analysis, time, software, personnel
One parameter to
give the inertia force
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Earthquake Analyses
Literature- Earthquake analyses
• Mononobe-Okabe Theory
• Richard-Elms Theory
• Full-Dynamic Analysis
-performed with use of Finite Element Software
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Westergaard Solution (1931)-Water Pressures on Dams during Earthquake-
Literature- Westergaard solution
• Two causes for added stresses during earthquake:
-accelerations of the mass of the dam-changes of water pressures
• Rigid vertical wall
• Horizontal acceleration
• No shear stresses
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Eurocode EN 1998-5
Literature- Eurocode EN 1998-5
• Hydrodynamic pressure on the outer face of the wall (Westergaard)
• Hydrodynamic pressure: water on both faces of the wall
2 x
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Numerical Modelling
Numerical Modelling- Introduction
• Westergaard Solution-Numerical investigation in Abaqus of Westergaard solution using two different approaches: water as an acoustic medium; water as a continuum.
• L-Shaped Retaining Wall-Check of the failure surface using pseudostatic analysis in Plaxis
2D AE
CAE
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Westergaard Solution
Numerical Modelling- Westergaard solution
20.5 m
4 m
64.5 m
4 m
Acoustic elements Acoustic elements
Infinite elements Infinite elements
- Type of elements- Resonance
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Westergaard Solution
Numerical Modelling- Westergaard solution
• Results
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L-Shaped Retaining Wall
Numerical Modelling- L-Shaped Retaining Wall
• Soil: M-C material
• Concrete: L-E material
• PGA=0.25g
3.7
m0.4
m
2 m
Total horizontal displacements
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L-Shaped Retaining Wall
Numerical Modelling- L-Shaped Retaining Wall
Total deviatoric strains
(a) Braja Das, Principles of Foundation Engineering, 2011
(b) Niels Krebs Ovesen, Lærebog i Geoteknik,, 2007
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Port of Beirut- New Quay Wall
Case Study- Introduction
8.5 m
Quay wall cross section (courtesy of Rambøll)
17 m
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Geometry of the Model and Geotechnical Conditions
Case Study- Introduction
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Pseudostatic Analysis
Case Study- Pseudostatic Analysis
• PGA= 0.25g
- Boundary conditions: standard fixities
- M-C Model for soil
- Static Young’s Modulus (average from the given range)
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Pseudostatic Analysis
Case Study- Pseudostatic Analysis
• Results
Horizontal displacement Deviatoric strain
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Dynamic Analysis
Case Study- Dynamic Analysis
- Boundary conditions: free field ; viscous
- Hardening soil model with small strain stiffness for fill material; - Linear- Elastic soil model for bedrock
- Dynamic Young’s Modulus (3-4 times the static one)
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Dynamic Analysis
Case Study- Dynamic Analysis
• Hardening Soil model with small strain stiffness
- Stress dependent stiffness
- Strain dependent stiffness
m=0
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Dynamic Analysis
Case Study- Dynamic Analysis
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Dynamic Analysis
Case Study- Dynamic Analysis
• Results- Horizontal Displacements
Maximum horizontal displacement [mm]
TH1 TH2 TH3
A 20 11 10
B 4.5 5 1
TH 1
TH 2
TH 3
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Dynamic Analysis
Case Study- Dynamic Analysis
• Results- T-H along the wall
Peak ground acceleration [g]
TH1 TH2 TH3
A 1.9 0.73 1.1
B 2.5 0.9 0.61
TH 1
TH 2
TH 3
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Conclusion and Further Research
Case Study- Dynamic Analysis
• Further research
• Analysis of the quay wall
-interface between the concrete blocks – relative movements-parametric study performed -displacement-based methods
Maximum horizontal displacement [mm]
EC8 Pseudostatic Dynamic
90 60 20
Analysis time [h]
Pseudostatic Dynamic
1 8-43
Thank you for your attention!