August 16, 2006 - University of California, Berkeley 1 OPENSEES Soil OPENSEES Soil OPENSEES Soil OPENSEES Soil-Pile Interaction Pile Interaction Pile Interaction Pile Interaction Study under Lateral Spread Loading Study under Lateral Spread Loading Study under Lateral Spread Loading Study under Lateral Spread Loading Po-Lam - EarthMechanics Pedro Arduino UW Peter Mackenzie-Helnwein UW 9/11/2008 Kinematic Analysis of Piles using OpenSees 2 Overview Introduction Background & Common Practice 3D Analysis of Soil-Pile Interaction Beam-Solid Approach Contact Formulation & Implementation Practical Applications Summary and Conclusions
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August 16, 2006 - University of
California, Berkeley 1
OPENSEES SoilOPENSEES SoilOPENSEES SoilOPENSEES Soil----Pile Interaction Pile Interaction Pile Interaction Pile Interaction Study under Lateral Spread LoadingStudy under Lateral Spread LoadingStudy under Lateral Spread LoadingStudy under Lateral Spread Loading
Po-Lam - EarthMechanics
Pedro Arduino UW
Peter Mackenzie-Helnwein UW
9/11/2008 Kinematic Analysis of Piles using OpenSees 2
Overview
� Introduction
� Background & Common Practice
� 3D Analysis of Soil-Pile Interaction
� Beam-Solid Approach
� Contact Formulation & Implementation
� Practical Applications
� Summary and Conclusions
August 16, 2006 - University of
California, Berkeley 2
9/11/2008 Kinematic Analysis of Piles using OpenSees 3
Problem DescriptionProblem DescriptionProblem DescriptionProblem Description
Kinematic loading on the pile from the upper unliquefied soil mass
displacing relative to the underlying stable lower soil mass
Slippage displacement concentrated on a usually thin liquefied soil layer
between the two stiffer soil masses
9/11/2008 Kinematic Analysis of Piles using OpenSees 4
Common Solution strategiesCommon Solution strategiesCommon Solution strategiesCommon Solution strategies
� Fixed-fixed beam
� Uncoupled free-field displacement
� Uncoupled displacement considering pile
pinning
� 2-D FEM analysis
� 3-D FEM analysis
August 16, 2006 - University of
California, Berkeley 3
9/11/2008 Kinematic Analysis of Piles using OpenSees 5
9/11/2008 Kinematic Analysis of Piles using OpenSees 18
GiDGiDGiDGiD post processing post processing post processing post processing Self Weight Self Weight Self Weight Self Weight ---- Vertical and Horizontal stresses due to self Vertical and Horizontal stresses due to self Vertical and Horizontal stresses due to self Vertical and Horizontal stresses due to self weight (notice near isotropic condition in liquefied layer)weight (notice near isotropic condition in liquefied layer)weight (notice near isotropic condition in liquefied layer)weight (notice near isotropic condition in liquefied layer)
Vertical Stress Horizontal Stress
Notice horizontal and vertical stresses are similar (fluid) in the liquefiable layer
August 16, 2006 - University of
California, Berkeley 10
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GiDGiDGiDGiD post processingpost processingpost processingpost processingInitial Conditions OpenSees
Vertical stresses Contact Forces
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9/11/2008 Kinematic Analysis of Piles using OpenSees 21
GiDGiDGiDGiD post processingpost processingpost processingpost processingσxx stresses after displacement
9/11/2008 Kinematic Analysis of Piles using OpenSees 22
GiDGiDGiDGiD post processingpost processingpost processingpost processingContact Forces at the end of displacement
Perspective View XZ Plane View
August 16, 2006 - University of
California, Berkeley 12
9/11/2008 Kinematic Analysis of Piles using OpenSees 23
GiDGiDGiDGiD post processingpost processingpost processingpost processingContours of Contact Forces at the end of Displacement
9/11/2008 Kinematic Analysis of Piles using OpenSees 24
GiDGiDGiDGiD post processingpost processingpost processingpost processingForces in the Beam at the End of Displacement
XZ Plane ViewPerspective View
August 16, 2006 - University of
California, Berkeley 13
9/11/2008 Kinematic Analysis of Piles using OpenSees 25
GiDGiDGiDGiD post processingpost processingpost processingpost processing
(a) Contact forces at soil-pile interface and (b) Horizontal pile forces at the end of loading
9/11/2008 Kinematic Analysis of Piles using OpenSees 26
GiD GiD GiD GiD Diagrams
Shear diagram Bending moment diagram
August 16, 2006 - University of
California, Berkeley 14
9/11/2008 Kinematic Analysis of Piles using OpenSees 27
Parametric StudyParametric StudyParametric StudyParametric Study
� Pile diameters � D1=2.50 m, D2=54in., and D3=24in.
� Soft Layer Thicknesses� T1=1D, T2 = 2D, and T4=4D.
� Piles stiffness, EI� (scale factors for base EI values
� “E-3”=0.125, “E-2”=0.25, “E-1”=0.50, “E0”=1.0, “E1”=2.0, “E2”=4.0, and “E3”=8.0.
� Total cases = 84 cases
9/11/2008 Kinematic Analysis of Piles using OpenSees 28
Final OpenSees MeshesFinal OpenSees MeshesFinal OpenSees MeshesFinal OpenSees Meshes
Finite element meshes for different soft layer thickness. (a)T=1D, (b)T=2D, and (c)T=4D
August 16, 2006 - University of
California, Berkeley 15
9/11/2008 Kinematic Analysis of Piles using OpenSees 29
Characteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyEffect of soil displacementEffect of soil displacementEffect of soil displacementEffect of soil displacement
9/11/2008 Kinematic Analysis of Piles using OpenSees 30
Characteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyEffect of pile stiffness EIEffect of pile stiffness EIEffect of pile stiffness EIEffect of pile stiffness EI
−2 −1.5 −1 −0.5 0 0.5 1 1.5 2
x 104
0
5
10
15
20
25
Moment in (kNm)
He
igh
t a
bo
ve
ba
se
in
(m
)
Moment distribution M for EI= 1195.00 MNm2
−4 −3 −2 −1 0 1 2 3 4
x 104
0
5
10
15
20
25
Moment in (kNm)
He
igh
t a
bo
ve
ba
se
in
(m
)
Moment distribution M for EI= 4780.00 MNm2
−12000 −10000 −8000 −6000 −4000 −2000 0 20000
5
10
15
20
25
Shear force in (kN)
Heig
ht above b
ase in (
m)
Shear force distribution V for EI= 1195.00 MNm2
−20000 −15000 −10000 −5000 00
5
10
15
20
25
Shear force in (kN)
He
igh
t a
bo
ve
ba
se
in
(m
)
Shear force distribution V for EI= 4780.00 MNm2
Location and value of maxV and maxM
varies for different EI
EI1less stiff
EI2stiffer
August 16, 2006 - University of
California, Berkeley 16
9/11/2008 Kinematic Analysis of Piles using OpenSees 31
Characteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyBasic definitionsBasic definitionsBasic definitionsBasic definitions
T
10D
10D
Leff/D
D
(Leff-T)/2D
9/11/2008 Kinematic Analysis of Piles using OpenSees 32
Characteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studymaxM and locationmaxM and locationmaxM and locationmaxM and location
11 12 13 14 15 16 17 18 19 20
−2
−1
0
1
2
3
x 104
pseudo time
Mom
ent M
in (
kN
m)
extreme values for moment M for EI= 2390.00 MNm2
abs(max M) in top layerabs(max M) in bottom layer
10 11 12 13 14 15 16 17 18 19 206
8
10
12
14
16
18
20
pseudo time
He
igh
t a
bo
ve
ba
se
in
(m
)
Location of extreme moments M for EI= 2390.00 MNm2
position of maxM in top layerposition of maxM in bottom layerL
effective
Leff
August 16, 2006 - University of
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Characteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyCharacteristic Results of Parametric studyPile deformationPile deformationPile deformationPile deformation
0 0.2 0.4 0.6 0.8 1 1.2 1.40
5
10
15
20
25
pile displacement (m)
de
pth
(m
)
9/11/2008 Kinematic Analysis of Piles using OpenSees 34
Non-dimensional characteristic parameter
� Es modulus o elasticity of stiff soil layer
� EI stiffness of pile
� T thickness of liquefiable layer
� D outer diameter of pile
2 2
sET D
EIβ =
August 16, 2006 - University of
California, Berkeley 18
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Embedment length in stiff soil layer (approximated as average of top and bottom layer)
9/11/2008 Kinematic Analysis of Piles using OpenSees 36
Dimensionless shear force demandshear force demandshear force demandshear force demand. Maximum shear occurs within the liquefied layer
0.0001
0.001
0.01
0.1
1
0.001 0.01 0.1 1 10 100
Es D^2 T^2 / EI
ma
xV
T^
2 D
/ E
I D
elt
a
Data Fit Es=5000 (54")
T=1D (2.50m) T=2D (2.50m)
T=4D (2.50m) T=1D (54")
T=2D (54") t=4D (54")
T=1D (24") T=2D (24")
T=4D (24") Es=5000 (54")
Es=12500 (54") Es=75000 (54")
Es=250000 (54")
August 16, 2006 - University of
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9/11/2008 Kinematic Analysis of Piles using OpenSees 37
Dimensionless bending momentbending momentbending momentbending moment (or curvature demand). Max M occurs at from the layer interface within the stiff layer
0.0001
0.001
0.01
0.1
1
0.001 0.01 0.1 1 10 100
Es D^2 T^2 / EI
ma
xM
T D
/ E
I D
elt
a
Data Fit Es=5000 (54")
T=1D (2.50m) T=2D (2.50m)
T=4D (2.50m) T=1D (54")
T=2D (54") t=4D (54")
T=1D (24") T=2D (24")
T=4D (24") Es=5000 (54")
Es=12500 (54") Es=75000 (54")
Es=250000 (54")
9/11/2008 Kinematic Analysis of Piles using OpenSees 38
9/11/2008 Kinematic Analysis of Piles using OpenSees 39
Dimensionless shear force demand. Maximum shear Dimensionless shear force demand. Maximum shear Dimensionless shear force demand. Maximum shear Dimensionless shear force demand. Maximum shear occurs within the liquefied layer.occurs within the liquefied layer.occurs within the liquefied layer.occurs within the liquefied layer.
0
0.05
0.1
0.15
0.2
0.25
0.001 0.01 0.1 1 10
Es D^2 T^2 / EI
ma
xV
T^
2 D
/ E
I D
elt
a
Data Fit T=1D (2.50m)
T=2D (2.50m) T=4D (2.50m)
T=1D (54") T=2D (54")
t=4D (54") T=1D (24")
T=2D (24") T=4D (24")
Es=5000 (54") Es=12500 (54")
Es=75000 (54") Es=250000 (54")
9/11/2008 Kinematic Analysis of Piles using OpenSees 40
Dimensionless bending moment (or curvature demand). Dimensionless bending moment (or curvature demand). Dimensionless bending moment (or curvature demand). Dimensionless bending moment (or curvature demand). Max M occurs at LMax M occurs at LMax M occurs at LMax M occurs at Lembedembedembedembed from the layer interface within the from the layer interface within the from the layer interface within the from the layer interface within the stiff layer.stiff layer.stiff layer.stiff layer.
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0.001 0.01 0.1 1 10
Es D^2 T^2 / EI
ma
xM
T D
/ E
I D
elt
a
Data Fit T=1D (2.50m)
T=2D (2.50m) T=4D (2.50m)
T=1D (54") T=2D (54")
t=4D (54") T=1D (24")
T=2D (24") T=4D (24")
Es=5000 (54") Es=12500 (54")
Es=75000 (54") Es=250000 (54")
August 16, 2006 - University of
California, Berkeley 21
9/11/2008 Kinematic Analysis of Piles using OpenSees 41
Comparison of fixed-fixed vs. OpenSees
Moment relative to Fixed-Fixed Beam
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.01 0.1 1 10
Es D^2 T^2/EI
Ca
l. M
om
en
t to
Fix
ed
-Fix
ed
Mo
men
t
9/11/2008 Kinematic Analysis of Piles using OpenSees 42