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OpenSeesGeotechnical Capabilities and Applications

Ahmed Elgamal Linjun Yan Zhaohui Yang

(U.C. San Diego)

PPEEEERR

2003 OpenSees User Workshop

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Dense sand above water table

Stiff clay below water tableMedium sand below water table

OpenSeesModeling of Bridge-Foundation-Soil Interaction

Mesh generated using GiD

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Soil Materials and Elements in OpenSees• Solid-fluid fully coupled plane-strain element, based on the u-pformulation of Zienkiewitz and Chan.

• Soil material models capable of simulating drained/undrainedcyclic behavior, including liquefaction and liquefaction-induced permanent ground deformation.

• For user convenience, predefined sets of material parameters are available for a wide range of soil types. Some of the parameters have been extensively calibrated based on experiments and field data. We will constantly update these material parameters to incorporate latest research results.

• Detailed explanation and examples are available at: http://opensees.berkeley.edu/ -> Projects -> Geotechnical -> U.C. San Diego or http://cyclic.ucsd.edu/opensees

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Soil Material: Pressure-Dependent Model

• multi-surface, non-associative plasticity model (for sand and silt), incorporating liquefaction effects.

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5

τ

P'

Failure surface

τ

γ

Soil Material: Pressure-Independent Model

• multi-surface, associative plasticity model (for clay and silt).

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Soil Material: Undrained Model

# Soil constitutive model: pressure-dependent materialnDMaterial PressureDependMultiYield 1 2 0.0 6.e4 1.8e5 35. …element quad 1 1 2 3 4 5.5 PlaneStrain 1 …

# Soil constitutive model: pressure-independent elementnDMaterial PressureIndependMultiYield 2 2 0.0 6.e4 2.e5 70. …# Undrained material coupling pressure-independent materialnDMaterial FluidSolidPorous 3 2 2 2.2e6element quad 2 6 7 8 9 5.5 PlaneStrain 3 …

• Coupled with pressure-dependent/independent material to simulate undrained soil response (e.g., soil below ground water table).

Example 1: define dry/drained soil element (e.g., above water table)

Define Soil Element in OpenSees

Example 2: define undrained soil element (e.g., below water table)

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Sample of Predefined Soil Material Parameters

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Soil Element: Solid-Fluid Fully Coupled Plane-Strain Quadrilateral Element

• Allows for pore water pressure generation & dissipation/redistribution.

4o

10 m

Sand(permeability 1.e-4 m/s)

Example:

10m mild infinite-slope sand profile (PressureDependMultiYield material) with 40 inclination, subjected to 0.2g sinusoidal base motion.

# Soil material: pressure-dependent materialnDMaterial PressureDependMultiYield 1 2 0.0 6.e4 1.8e5 35. …# Solid-fluid fully coupled elementelement quadUP 1 1 2 3 4 5.5 PlaneStrain 1 …

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Soil Element: Solid-Fluid Fully Coupled Plane-Strain Quadrilateral Element

• Compared to undrained material, which only allows for pore water pressure generation, but not dissipation/redistribution:

Undrained material + quad Element quadUP Element

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Experimental Stress Path (Kammerer, Pestana, Seed)

-10.0

-5.0

0.0

5.0

10.0

15.0

0.0 10.0 20.0 30.0 40.0

Effective vertical stress (kPa)

Shea

r str

ess

(kPa

)

Effective Stress Path (Simulation)

-10.0

-5.0

0.0

5.0

10.0

15.0

0.0 10.0 20.0 30.0 40.0

Effective vertical stress (kPa)

Shea

r str

ess

(kPa

)

Shear Stress-Strain (Simulation)

-10.0

-5.0

0.0

5.0

10.0

15.0

-0.5% 0.5% 1.5% 2.5%

Shear strain

Shea

r str

ess

(kPa

)

Experimental Shear Stress-Strain (Kammerer, Pestana, Seed)

-10.0

-5.0

0.0

5.0

10.0

15.0

-0.5 0.5 1.5 2.5

Shear strain (%)

Shea

r str

ess

(kPa

)

Sample of Experimental Data and Soil Model Calibration(UC Berkeley Simple Shear Test: Pestana, Seed, and Kammerer)

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PEER Testbed: Humboldt Bay, Middle Channel Bridge

• Humboldt Bay Bridge is located near Eureka in northern California

• 330 meters long, 9-span composite bridge with precast/prestressedconcrete I-girders and cast-in-place concrete slab

• Each pier is supported on a group of 5 to 16 piles

• The foundation soil is composed mainly of dense fine–to-medium sand, organic silt and stiff clay layers

Other Participants in Humboldt Bridge Modeling:Prof. Joel Conte Mr. Yuyi Zhang Mr. Gabriel Acero

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Modeling Structural Components Using Nonlinear Fiber Beam-Column Element

Reinforcing Steel

Unconfined concrete Confined concrete

Reinforcing steel

Unconfined concrete Confined concrete

-0.03 -0.02 -0.01 0 0.01 0.02 0.03-1

0

1

2

3

4

5

6

7

8

Strain

Stre

ss

-0.02 -0.015 -0.01 -0.005 0 0.005 0.01 0.015 0.02-100

-80

-60

-40

-20

0

20

40

60

80

100

Strain

Stre

ss

Concrete Material: uniaxialMaterial Concrete01

Reinforcement: uniaxialMaterial Steel01

Columns Piles

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Monotonic Pushover (Single Column on Fixed Base)

0 1 2 3 4 5x 10-3

0

2

4

6

8

10

12 x 104

Curvature (/in)

Mom

ent (

kips

-in)

0 1 2 3 4 5x 10-3

0

2

4

6

8

10

12 x 104

Curvature (/in)

Mom

ent (

kips

-in)

Cyclic Pushover (Single Column on Fixed Base)

-1 -0.5 0 0.5 1x 10

-3

-1

-0.5

0

0.5

1 x 105

Curvature (/in)M

omen

t (ki

ps-in

)

-1 -0.5 0 0.5 1x 10

-3

-1

-0.5

0

0.5

1 x 105

Curvature (/in)M

omen

t (ki

ps-in

)

Modeling Structural Components Using Nonlinear Fiber Beam-Column Element

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0 2 4 6 8 10 12 14 16 18 20

-0.2

0.0

0.2

0.4

-0.2

0.0

0.2

0.4

-0.2

0.0

0.2

0.4

y-direction (vertical)

Time (second)

z-direction (transversal)

Acce

lere

tion

(g)

x-direction (longitudinal)

rock outcropping motion (total) incident wave at model base (by deconvolution)

3D Incident Base Excitation

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y-displacement (m)

x-displacement (m)

Lateral and Vertical Displacement Results

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excess porepressure ratio

Excess Pore Pressure Results

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Original position Position after deformation

P1 P2 P3 P4 P5 P6 P7 P8

(Deformations are amplified)

Deformed Shape of Bridge-Foundation System

0 5 10 15 20-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 5 10 15 20-0.15

-0.12

-0.09

-0.06

-0.03

0.00

0.03

0.06

excess pore pressure ratio of support soil

settlement of abutment top soil

Excess Pore Pressure R

atio

Settl

emen

t (m

)

Time (second)

Correlation between Soil Settlement and

Excess Pore Pressure

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0

1000

2000

3000

4000

5000

0

1000

2000

3000

4000

5000

0 5 10 15 20-15000

-10000

-5000

0

5000

10000

15000

-0.0010 -0.0005 0.0000 0.0005 0.0010 0.0015-15000

-10000

-5000

0

5000

10000

15000

(a)

moment in xy plane

(b)

moment in yz plane

(c)

mom

ent (

KN

-m)

time (second)

(d)

curvature

Moment-Curvature Response in Columns

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2D Bridge Model in OpenSees(Conte/Zhang/Acero)

• Generated by Mr. Yuyi Zhang, using GID mesh generator (http://gid.cimne.upc.es)

Water Table

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Eigen Analysis to Obtain Natural Periods and Mode Shapes (Conte/Zhang/Acero)

• Mode 1: T1 = 1.23 sec

• Mode 2: T2 = 1.17 sec

#Compute the first 2 eigenvalues and eigenvectorseigen 2# Print mode shapes (eigenvectors) to fileprint eigenVectFile -node $all_nodes

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Transient Analysis: System Response

• Permanent deformation at the end of the shaking: earthquake-induced soil lateral spreading mechanism

(Conte/Zhang/Acero)

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2D Transient Analysis: Soil Response (Conte/Zhang/Acero)

• Soil: Time histories of excess pore water pressure

0 5 10 15 20-100

-50

0

50

100

150

200

250Soil Element 2450

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)

0 5 10 15 20-100

-50

0

50

100

150

200

250Soil Element 2450

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)Po

re P

ress

ure

[kPa

]

0 2 4 6 8 10 12 14 16 18 20-50

0

50

100

150

200

250

300

350Soil Element 1276

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)

0 2 4 6 8 10 12 14 16 18 20-50

0

50

100

150

200

250

300

350Soil Element 1276

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)Po

re P

ress

ure

[kPa

]

0 5 10 15 20-50

0

50

100

150

200

250

300

350

400

450

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)

Soil Element 315

0 5 10 15 20-50

0

50

100

150

200

250

300

350

400

450

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)

Soil Element 315

Pore

Pre

ssur

e [k

Pa]

0 5 10 15 20-50

0

50

100

150

200Soil Element 191

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)

0 5 10 15 20-50

0

50

100

150

200Soil Element 191

Time (sec)

Exc

ess

Por

e P

ress

ure

(KP

a)Po

re P

ress

ure

[kPa

]

A B CD

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2D Transient Analysis: Soil Response (Conte/Zhang/Acero)

• Soil: Shear stress vs. shear strain response

-0.01 -0.005 0 0.005 0.01 0.015 0.02-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 2450

-0.01 -0.005 0 0.005 0.01 0.015 0.02-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 2450

She

ar S

tress

[kP

a]

-5 0 5 10 15x 10

-3

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 1276

-5 0 5 10 15x 10

-3

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 1276

She

ar S

tress

[kP

a]

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02-150

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 315

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02-150

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 315

She

ar S

tress

[kP

a]

-0.01 -0.005 0 0.005 0.01-150

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 191

-0.01 -0.005 0 0.005 0.01-150

-100

-50

0

50

100

150

Shear Strain

She

ar S

tress

(KP

a)

Soil Element 191

She

ar S

tress

[kP

a]

A B CD

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Contact Information

• Detailed explanation and examples for soil materials/elements are available at: http://opensees.berkeley.edu/ -> Projects -> Geotechnical -> U.C. San Diegoor http://cyclic.ucsd.edu/opensees

• For more information, please contact: Zhaohui Yangzhyang@ucsd.eduTel: (858) 822-0058