Earthquake Design of Retaining Structures Master thesis
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Transcript of Earthquake Design of Retaining Structures Master thesis
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
22/10/2015Earthquake Design of Retaining Structures3 Dansk Geoteknisk Forening, Aarhus
Problem Statement
Introduction-Problem Statement
Water Backfill + WaterWall
Static forces Dynamic forces
22/10/2015Earthquake Design of Retaining Structures4 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures5 Dansk Geoteknisk Forening, Aarhus
Earthquake Analyses
Literature- Earthquake analyses
• Mononobe-Okabe Theory
• Richard-Elms Theory
• Full-Dynamic Analysis
-performed with use of Finite Element Software
22/10/2015Earthquake Design of Retaining Structures6 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures7 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures8 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures9 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures10 Dansk Geoteknisk Forening, Aarhus
Westergaard Solution
Numerical Modelling- Westergaard solution
• Results
22/10/2015Earthquake Design of Retaining Structures11 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures12 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures13 Dansk Geoteknisk Forening, Aarhus
Port of Beirut- New Quay Wall
Case Study- Introduction
8.5 m
Quay wall cross section (courtesy of Rambøll)
17 m
22/10/2015Earthquake Design of Retaining Structures14 Dansk Geoteknisk Forening, Aarhus
Geometry of the Model and Geotechnical Conditions
Case Study- Introduction
22/10/2015Earthquake Design of Retaining Structures15 Dansk Geoteknisk Forening, Aarhus
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)
22/10/2015Earthquake Design of Retaining Structures16 Dansk Geoteknisk Forening, Aarhus
Pseudostatic Analysis
Case Study- Pseudostatic Analysis
• Results
Horizontal displacement Deviatoric strain
22/10/2015Earthquake Design of Retaining Structures17 Dansk Geoteknisk Forening, Aarhus
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)
22/10/2015Earthquake Design of Retaining Structures18 Dansk Geoteknisk Forening, Aarhus
Dynamic Analysis
Case Study- Dynamic Analysis
• Hardening Soil model with small strain stiffness
- Stress dependent stiffness
- Strain dependent stiffness
m=0
22/10/2015Earthquake Design of Retaining Structures19 Dansk Geoteknisk Forening, Aarhus
Dynamic Analysis
Case Study- Dynamic Analysis
22/10/2015Earthquake Design of Retaining Structures20 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures21 Dansk Geoteknisk Forening, Aarhus
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
22/10/2015Earthquake Design of Retaining Structures22 Dansk Geoteknisk Forening, Aarhus
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