opensees in practice: soil structure...
TRANSCRIPT
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OpenSees in Practice:Soil Structure Interaction
Arash KhosravifarFugro Consultants, Inc.August 16, 2012
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Examples1.Piles in Liquefied Soils – 2D Approach (UC Davis with Professor Ross Boulanger)
2.Piles in Liquefied Soils – 3D Approach (UC Davis)
3.Soil-Pile-Interaction for a Suspension Bridge (Fugro)
4.Seismic Retrofit of an Immersed Tunnel (Fugro)
5.OpenSees Components and Calibration Process
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Example 1.Piles in Liquefied Soils – 2D Approach
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Piles in Liquefied Soils – 2D Approach
• Large diameter extended pile shafts (2 to 3 m) can be an effective choice in areas of potential lateral spreading.
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FE model• OpenSees FE framework• Soil elements
9-4 Quad UPPDMY02 and PIMY
• Pile elementsDisp-based beam columnFiber section
• Interface elementsPYSimple and PYLiq1
CG
Dense sand(N1)60 = 35
Loose sand(N1)60 = 5
Clay crustSu = 40 KPa
Ground surface
qz
py
tz
0 m
-5 m
-8 m
-20 m
+10 m
2m diam
every0.5 mg
αg
g
Piles in Liquefied Soils – 2D Approach
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Animation
Piles in Liquefied Soils – 2D Approach
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0.01 0.1 1 10
Period (s)
0.01
0.1
1
10
(a) Base ground motions
0.01 0.1 1 10
Period (s)
0.01
0.1
1
10(b) Ground surface - nonliquefied
(Su=40kPa)
0.01 0.1 1 10
Period (s)
0.01
0.1
1
10
(c) Ground surface - liquefied(Su=40kPa)
Piles in Liquefied Soils – 2D Approach
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Example 2. Piles in Liquefied Soils – 3D Approach
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Piles in Liquefied Soils – 3D Approach
• Fully coupled (3D continuum)• Modeled in OpenSeesPL
• No interface element
• Pile occupies a space
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Animation
Piles in Liquefied Soils – 3D Approach
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Example 3. Soil-Pile-Interaction for a Suspension BridgeArash Khosravifar, Thaleia Travasarou, Jose Ugalde and Weiyu Chen, Fugro
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Foundation
Soil-Pile-Interaction for a Suspension Bridge
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Site Investigation
Soil-Pile-Interaction for a Suspension Bridge
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Produce Kinematic Motions• Site Response Analysis• Soil-Pile-Interaction
Modeled in OpenSeesPL
Soil-Pile-Interaction for a Suspension Bridge
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Site Response Analyses Results (no pile)• Comparison with FLAC3D and Deepsoil
20 ft below surface
0
0.1
0.2
0.3
0.4
0.5
0.6
0.01 0.1 1 10
Period (s)
PSA (g)
OpenSees
Deepsoil
FLAC
Soil-Pile-Interaction for a Suspension Bridge
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Soil-Pile-Interaction (single pile pushover)
Soil-Pile-Interaction for a Suspension Bridge
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Soil-Pile-Interaction (single pile pushover)
Clay
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 1 2 3 4 5 6 7
Disp (ft)
P (lb
/ft)
API Clay at 45 ft
FLAC at 40 ft
FLAC at 50 ft
OpenSees at 46 ft
Clay
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
0 1 2 3 4 5 6 7
Disp (ft)
P (lb
/ft)
API Clay at 45 ft
OpenSees at 46 ft
Without using interface springs With using interface springs
Soil-Pile-Interaction for a Suspension Bridge
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Example 4. Seismic Retrofit of an Immersed TunnelLanka Ilankatharan and Thaleia Travasarou, Fugro
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Seismic Retrofit of An Immersed TunnelLanka Ilankatharan and Thaleia Travasarou, Fugro
OpenSees FE mesh PressureDependMultiYield (PDMY01)
PressureIndependMultiYield (PIMY)
Representative X-Section
4-node quadUP
Potentially liquefiable
Franciscan
Stiff ClayStiff Clay
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Total displacement contours
units: feet
Horizontal disp. contours & Total disp. vectors
units: feet
Seismic Retrofit of An Immersed TunnelLanka Ilankatharan and Thaleia Travasarou, Fugro
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Horizontal displacement contours (OpenSees)
Horizontal displacement contours (FLAC-2D)
X-displacement contours -4.00E+00 -2.00E+00 0.00E+00 2.00E+00 4.00E+00 6.00E+00 8.00E+00 1.00E+01 1.20E+01 1.40E+01
Contour interval= 2.00E+00
11-16 ft
10-14 ft ~3 ft
~3 ft
Seismic Retrofit of An Immersed TunnelLanka Ilankatharan and Thaleia Travasarou, Fugro
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Example 5. OpenSees Components and Calibration
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OpenSees Components and Calibration
• Soil models 9-4 Quad UP, Quad UP, Brick UP elementsPDMY02 and PIMY
• Pile elementsDisp-based beam column, Flexibility-based beam columnFiber section
• Interface elementsPYSimple1, TZSimple1, QZSimple1PYLiq1, TZLiq1 (for liquefaction)
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0 0.01 0.02 0.03 0.04
Shear strain γ12
0
100
200
300
400
Shea
r str
ess
τ 12 (
KPa
)
(N1)60 = 5
σ′vc = 100 KPa
σ′vc = 800 KPa
0 200 400 600 800 1000
Vertical effective stress (KPa)
0
100
200
300
400
Shea
r str
ess
τ 12 (
KPa
)
(N1)60 = 5
σ′vc = 100 KPa
σ′vc = 800 KPaφ'DSS = 30º
0 0.02 0.04 0.06 0.08 0.1
γ12 and γoct
0
20
40
60
τ 12 a
nd τ
oct (
KPa
)
(N1)60 = 5τ12 vs. γ12
τoct vs. γoct
0 40 80 120
σ′v and p′ (KPa)
0
20
40
60
τ 12 a
nd τ
oct (
KPa
)
(N1)60 = 5τ12 vs. σ′vτoct vs. p′
φ'DSS = 30º
φ'oct = 25.4º
Undrained Monotonic Direct-Simple-Shear Test (DSS)
Drained Monotonic DSS
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Drained Cyclic DSS
1E-006 1E-005 0.0001 0.001 0.01 0.1
Shear strain, γ12
0
0.2
0.4
0.6
0.8
1
Gse
c/Gm
ax
EPRI (1993)for depth 0-6 mand 36-76 m
σ′vo = 100 KPaσ′vo = 800 KPa
1E-006 1E-005 0.0001 0.001 0.01 0.1
Shear strain, γ12
0
20
40
60
Equi
v. d
ampi
ng ra
tio (%
)
EPRI (1993)for depth 0-6 mand 36-76 m
σ′vo = 100 KPaσ′vo = 800 KPa
-0.04 -0.02 0 0.02 0.04
Shear strain, γ12
-0.8
-0.4
0
0.4
0.8
Shea
r str
ess
ratio
(τ/σ
′ vc)
(N1)60 = 5σ′vc = 100 KPa
-0.04 -0.02 0 0.02 0.04
Shear strain, γ12
-0.8
-0.4
0
0.4
0.8
Shea
r str
ess
ratio
(τ/σ
′ vc)
(N1)60 = 5σ′vc = 800 KPa
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Undrained cyclic behavior• Calibrated for Cyclic Resistance Ratio (CRR)
1 10 100
Number of uniform cycles
0
0.2
0.4
0.6
(N1)60 = 25
(N1)60 = 15
(N1)60 = 5
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Structural Elements
2 m
Steel rebars63 #11
Unconfined concreteConfined concrete
0 0.02 0.04 0.06 0.08
Curvature (1/m)
0
20000
40000
60000
Mom
ent (
KN
-m) (a)
(b) (c) (d)
(a) First rebar yield(b) Unconfined concrete (cover) crush(c) Confined concrete (core) crush(d) Rebar snap
• Fiber sections
• Displacement-based nonlinear beam column elements
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Soil Springs
• Update properties based on PWP
• Allow gap formation
