Geotechnical and SSI Simulations

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Geotechnical and SSI Simulations

Ahmed Elgamal

Jinchi Lu

Zhaohui Yang

1A. Elgamal Sept 2008

Yuyi Zhang, Joel P. Conte, Zhaohui Yang, Ahmed Elgamal, Jacobo Bielak, and Gabriel Acero, Two-

Dimensional Nonlinear Earthquake Response Analysis of a Bridge-Foundation-Ground System,

Earthquake Spectra, Volume 24, No. 2, pages 343–386, May 2008, Earthquake Engineering Research

Institute


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2-D Finite Element Model in OpenSeesProf. Joel Conte, Joint Research

• Plane strain condition

• 11,000 nodes and 10,900 elements; 20,000 DOF’s

• 370 beam-column elements

• 9,900 quadrilateral “soil” elements

• 590 zero-length elements3A. Elgamal Sept 2008

ZeroLength Element ZeroLength Element

Column

Beam

Gap & Hook

Beam

Gap & Hook

• Expansion joints: Zero-length elements with gap-hook material

Superstructure Joints

1/2” Expanded Joint

Filler All Around

Shear Key

5 #4 Rebars

per Key

Cap Beam

Superstructure

• Abutment joints: Zero-length elements with gap-hook material

ZeroLength Element ZeroLength Element

Column

Beam

Gap & Hook

Beam

Gap & Hook

1/2” Expanded Joint

Filler All Around

Shear Key

5 #4 Rebars

per Key

Cap Beam

Superstructure


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OpenSees 3D FE Model • 30,237 nodes

• 1,140/280 linear/nonlinear beam-column elements

• 81 linear shell elements

• 23,556 solid brick elements

• 1,806 zero-length elements

Transverse and Longitudinal Response

3D Spatial Configuration

Abutments

Pile Foundations

Ground

Three-Dimensional Seismic Response of Humboldt Bay

Bridge-Foundation-Ground System, A. Elgamal,

L. Yan, Z. Yang, and J. P. Conte, Journal of

Structural Engineering, Vol. 134, No. 7, July 1, 2008.

A. Elgamal Sept 2008 5

Piers and Pile Groups (Fiber Discretization of Pier and Pile Cross-Sections)

(Prof. P. Fillippou)

Bilinear

Kent-Scott-Park model


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(1) Rock outcrop motion

Deconvolu

tion

Usin

g S

hake91

(2) Incident motion at the top of bedrock (2)

Pro

pagation

Usin

g S

hake91

(3) Incident motion at FE model base

Soil profile

Shear Wave Velocity (m/s)

Depth

(m

)

0 200 400 600 800 10000

40

80

120

160

200

240

Rock

profile

Measured

Model

Idealization

Definition of Seismic Excitation (Engineering Seismology)

Stage I

Stiff spring

Stage II

Equivalent

supporting force

Equivalent

earthquake forceDashpot

1σ ′

2σ ′

3σ ′

321 σσσ ′=′=′

Note: Tied node condition on lateral boundaries (shear beam concept) 7A. Elgamal Sept 2008

1 2 3

4

Elevation and Plan View

of Residual Deformation

(Scaling Factor = 50)


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Three-Dimensional Seismic Response of Humboldt Bay

Bridge-Foundation-Ground System, A. Elgamal,

L. Yan, Z. Yang, and J. P. Conte, Journal of Structural

Engineering, Vol. 134, No. 7, July 1, 2008.

A. Elgamal Sept 2008 9

Numerical Analysis

Permanent Deformation of Bridge, Foundations, and Abutments

Original position Final position with residual deformation

#1 Pier

& pile

group

#2 Pier

& pile

group

#3 Pier

& pile

group

#4 Pier

& pile

group

#5 Pier

& pile

group

#6 Pier

& pile

group

#7 Pier

& pile

group

#8 Pier

& pile

groupLeft

abutment

Right

abutment

Original position

Final position with residual deformation

(a) Elevation view (exaggerated scale by a factor of 50)

(b) Plan view (exaggerated scale by a factor of 150)


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Shallow Foundation Settlement due to Liquefaction

(Scale factor for deformed meshes: 10)

Untreated case

Treated by compaction and high permeability

Treated by stone columns

0 20 40 60 80 100 120 140 160 180

−0.25

−0.2

−0.15

−0.1

−0.05

0

Time (sec)

Ver

tical

dis

plac

emen

t (m

) Medium Sand (LMS) Dense Gravel (LDG)Stone Column (LSC)

Foundation settlement time histories

0 10 20 30 40 50 60 70 80 90 100−0.2

−0.15

−0.1

−0.05

0

0.05

0.1

0.15

0.2

Time (sec)

Accele

ration (

g)


US-Japan Cooperative Research (2003-2005)


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1.8m high, UCSD Shake table tests (Prof. Dobry, RPI Test Setup

Laminar container provided by Prof. Scott Ashford, UCSD


Experiment Preparation


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UCSD Shake table test


Shaking Table Tests: US-Japan Research (NSF, NIED, PEER, CALTRANS)

5m height: Liquefaction-Induced lateral Spreading Effects on Piles (NIED, Tsukuba)

Professor Kohji Tokimatsu, Dr. Masayoshi Sato, and Dr. Akio Abe

NIED, Tsukuba, Japan


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Before After

1m of Lateral Spreading ( > 3 pile diameters)

NIED, Tsukuba, Japan17A. Elgamal Sept 2008


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Gravel Drain/Stone column Ground Modification

a) Isometric view

b) Pile head close-up

Finite element mesh for the 3x3 pile group. 26A. Elgamal Sept 2008

User Interface for Pile-ground systems

http://cyclic.ucsd.edu/openseespl

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0

0.05

0.1

0.15

0.2

0.25

0.3

2 3 4 5 6 7 8

Spacing (xD)

Pile h

ead

defl

ecti

on

(in

) 3x3 pile group

Single pile

Pile group displacement of the 3x3 pile group (for

different spacing) and the single pile under lateral

loading.


OpenSees Computations through Graphical Interface OpenSeesPL

Spacing = 2D

Spacing = 3D28A. Elgamal Sept 2008


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Spacing = 4D



Spacing = 6D



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Spacing = 8D



Chapter 6 Examples

6.1 Example 1: Linear Pile in Rigid Ground

6.2 Example 2: Linear Pile in Loose Sand

6.3 Example 3: Linear Pile in Medium Sand

6.4 Example 4: Nonlinear Pile in Linear Soil

6.5 Example 5: Saturated Medium Sand

6.6 Example 6: Stone Columns

6.7 Example 7: Pile in Sloping Ground

Appendix A Benchmark Linear Finite Element Analysis of Laterally Loaded Single Pile

Using OpenSees & Comparison with Analytical Solution

Appendix B Finite Element Analysis of Arkansas Test Series Pile #2 Using Opensees

(with LPILE Comparison)

Appendix C Finite Element Analysis of Standard CalTrans 16" CIDH Pile Using

Opensees for General Comparison with LPILE (with Default P-Y Multiplier = 1.0)

Appendix D Finite Element Analysis of Caltrans 42" CIDH Pile Using OpenSees for

General Comparison with LPILE (with Default P-Y Multiplier = 1.0)

Appendix E Finite Element Analysis of Standard CalTrans 16" CIDH Pile Subjected to

Axial Load

Appendix F Moment-Curvature Analysis of Circular Nonlinear RC Beam (Fiber

Section)


OpenSeesPL Manual Examples

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OpenSeesPL: http://cyclic.ucsd.edu/openseespl




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Documents

Geotechnical and SSI Simulations