SOIL-STRUCTURE-INTERACTION SIMULATION MODELS · 2012. 8. 22. · SOIL-STRUCTURE-INTERACTION...

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SOIL-STRUCTURE-INTERACTION SIMULATION MODELS Juan M. Pestana University of California, Berkeley PEER 2001 Annual Meeting Oakland, California. January 26, 2001 RESEARCH SUPPORTED BY THE PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER IN COLLABORATION WITH THE CALIFORNIA DEPARTMENT OF TRANSPORTATION AND THE NATIONAL SCIENCE FOUNDATION

Transcript of SOIL-STRUCTURE-INTERACTION SIMULATION MODELS · 2012. 8. 22. · SOIL-STRUCTURE-INTERACTION...

  • SOIL-STRUCTURE-INTERACTIONSIMULATION MODELS

    Juan M. Pestana

    University of California, Berkeley

    PEER 2001 Annual Meeting

    Oakland, California. January 26, 2001

    RESEARCH SUPPORTED BY THE PACIFIC EARTHQUAKE ENGINEERING RESEARCH CENTER IN COLLABORATIONWITH THE CALIFORNIA DEPARTMENT OF TRANSPORTATION AND THE NATIONAL SCIENCE FOUNDATION

  • SEISMIC SSI- CONCLUSIONS Key components are: (foundation) soil, foundation system &

    structure.

    Key issue of Performance Based Design is the evaluation(estimation) of performance -> Requirement of robust, efficient &realistic numerical- analytical description of material response &system.

    Development & refinement of laboratory experiments which canaccurately represent the problem are essential to validateindividual constructs (numerical/conceptual blocks). It thereforeprovides an invaluable resource for calibrating numerical Codes->Reduce inherent modeling uncertainty.

    Successful development of coupled site response and Soil-Pile-Superstructure Interaction analyses provides a Comprehensiveframework for Performance Based Design for increasingly highershaking levels

  • Geotechnical EngineersView of the World

    Geotechnical Geotechnical EngineerEngineerssView of the WorldView of the World

    Structural EngineersView of the World

    Structural EngineerStructural EngineerssView of the WorldView of the World

    Courtesy of Dr. Lehman- University of Washington

  • SOIL-STRUCTURE INTERACTION

    Types of structures (buildings, bridges, bunkers)

    Transfer Function: Empirically or analyticaldescription of the behavior of a structure givenresponse at ground level.

    Estimation of performance Shallow foundations- A lot of work still needed (i.e.,

    mat foundation). A lot of interest - effect of structureembedment.

    Deep Foundations- A lot of interest- Highway/retrofit of Bridges and other structures in soft soils-SSI is extremely important.

  • SSI- DEEP FOUNDATIONSSoil-Pile-Superstructure Interaction

    Coupled Model

    Earthquake Motion

    Overall Response

    Modal Mass

    input time history

  • Large Scale Shaking Table Tests

    Seismic Soil- Pile Group-Structure Interaction Test

  • Far field element:radiation damping =f(soil nonlinearity innear and free field)

    Soil Model

    Interface element:gapping = f(plasticsoil deformation)

    Near field element:partitioned dynamic nonlinearp-y/t-z spring = f(strain rate,#cycles, strain reversals)

    Conceptual Soil - Pile Model

    Interface Near field Far field Free field

    Free field element:time domain site responseinputs motions at nodes

    k1 k2 k3

    c1 c2 c3

    Modal Mass

    input time history

    Pilegap

  • NONLINEAR SITE RESPONSEANALYSES- MODEL

    • KEY ELEMENTS:• ABILITY TO MODEL SMALL

    STRAIN NON-LINEARITYAND DAMPINGCHARACTERISTICS

    • FLEXIBILITY TOREALISTICALLY DESCRIBERESPONSE FROM SMALL TOLARGE STRAINS

    • CORRESPONDENCE WITHMEASURED SOIL BEHAVIOR- ESTABLISHED PARAMETERDETERMINATION

    • CHARACTERIZATION OFUNCERTAINTY

    10-4

    10-2

    100

    0

    0.5

    1Modulus Degradation for Clay ( Vucetic & Dobry)

    G/G

    max

    10-4

    10-2

    100

    0

    10

    20

    30Damping for Clay (Vucetic & Dobry)

    Shear Strain (%)

    Dam

    ping

    Rat

    io (

    %)

    model

    model(Vucetic & Dobry)

    (Vucetic & Dobry)

  • TESTSERIES 1.1

    CROSS-SECTION

  • 5%

    Dam

    ped S

    pect

    ral A

    ccele

    ratio

    n (g)

    Elev 0

    Elev -8

    Elev -18

    Elev -30

    Elev -48

    0

    2

    0

    2

    0

    2

    0

    2

    0

    2

    NONLINEAR SITE

    RESPONSE ANALYSIS

    CALIBRATEDwith

    VERTICALARRAY

    INFORMATION

    SPECTRAL ACCELERATION

    5% D

    ampe

    d S

    pect

    ral A

    ccel

    erat

    ion

    (g

    Period (sec)0.01 0.1 1 10

    0

    Modal Mass

    input time history

  • Formulationof nonlinear1-D element

    Nonlinear element

    Gap element

    Friction element

    PileFar field

    =

    +

    +

    y/yc

    p/pul

    t

    p-y element

    gap element nonlinear element

    friction element

    y/yc

    pgap

    /pult

    y/yc

    p/pul

    t

    y/yc

    pfric

    tion

    /pult

    -1.0

    1.0

    1.0-1.0

    -1.0

    1.0

    1.0-1.0

    -1.0

    1.0

    1.0-1.0

    -1.0

    1.0

    1.0-1.0

    ygap

  • NUMERICAL CAPABILITIES -NONLINEAR p-y, t-z springs with Gapping Capabilities

    -1

    -0.5

    0

    0.5

    1

    -8 -6 -4 -2 0 2 4 6 8

    y/yc

    p/p

    u

    p-y curve for clay

    p-y w/ gap (loop 1)

    p-y w/ gap (loop 2)

    Pilegap

  • -8

    0

    8

    -8

    0

    8

    -0.5 0 0.5Deflection Y (in)

    -8

    0

    8

    -0.5 0 0.5Deflection Y (in)

    depth = 4d depth = 5d

    depth = 6d depth = 7d

    depth = 8d depth = 9d

    Soi

    l Res

    ista

    nce

    P (l

    b/in

    )

    Calculated

    Test Data

    NEAR FIELD RESPONSE

    Modal Mass

    input time history

  • FOUNDATION RESPONSE- BENDING MOMENTS

    D

    6543210

    Depth

    (ft)

    S3

    0 0.5 1Bending Moment (k-in)

    6543210

    Depth

    (ft)

    S4

    6543210

    Depth

    (ft)

    S1

    6543210

    Depth

    (ft)

    S2

    ft)

    S3

    Modal Mass

    input time history

  • PREDICTION OF STRUCTURAL RESPONSE

    Modal Mass

    input time history

    PS

    A (g

    )

    0

    1

    2

    3

    4

    5

    PS

    A (g

    )

    S3

    0.01 0.1 1 10Period (sec)

    0

    1

    2

    3

    4

    5

    PS

    A (g

    )

    S4

    0

    1

    2

    3

    4

    5

    PSA

    (g)

    S1

    0

    1

    2

    3

    4

    5

    PSA

    (g)

    S2

    PSA

    (g)

    PSA

    (g)

    PSA (g)PSA (g)PSA (g)PSA (g)

  • STRUCTURALRESPONSE

    Compute

    d Tp (sec

    )

    5

    Compute

    d Max. Sa

    (g)

    0 0.4 0.8 1.2 1.6 2Recorded amax (g)

    0

    0.4

    0.8

    1.2

    1.6

    2

    Compute

    d amax (g

    )

    S1S2

    S3

    S4

    (a)

    0 0.1 0.2 0.3Recorded Tp (sec)

    0

    0.1

    0.2

    0.3

    Comp

    uted T

    p (se

    c)

    S1

    S3

    0 1 2 3 4 5Recorded Max. Sa (g)

    0

    1

    2

    3

    4

    5

    Comp

    uted M

    ax. S

    a (g)

    S1

    S2

    S3S4

    (b)

    (c)

    S2

    S4

  • Performanceof Pile GroupsEquivalent Pier

    Approach

    0.0

    1.0

    2.0

    3.0S

    pect

    ral A

    ccel

    erat

    ion

    (g) Recorded

    e=1.0

    e=0.8

    e=0.6

    e=0.4

    e=0.2

    0.01 0.1 1 1 0Period (sec.)

    0.0

    1.0

    2.0

    3.0

    Spec

    tral

    Acc

    eler

    atio

    n (g

    ) Recordede=1.0

    e=0.8

    e=0.6

    e=0.4

    e=0.2

    Response of Structure

    Response of Pile Cap

    Damping=5%

    Damping=5%

    0

    0.2

    0.4

    0.6

    0.8

    1

    0 0.2 0.4 0.6 0.8 1

    Input MHA

    p-y

    eff

    icie

    ncy

    2x2 pile gr

    3x3 pile gr

  • Multidirectional Shaking2-D & 3-D Site Response Analyses

    -0.06

    -0.04

    -0.02

    0.00

    0.02

    0.04

    0.06

    0.08

    -0.06 -0.04 -0.02 0.00 0.02 0.04 0.06 0.08

    Fault Parallel Sur

    Fault Normal Surface Motion (m)

    Pacoima Dam recorda

    max = 0.05g

    50 m Soil Profile

  • -10.0

    -5.0

    0.0

    5.0

    10.0

    -0.4 -0.2 0 0.2 0.4

    5 %10 %

    20 %50 %API

    Normalized For

    u.d.L)

    Symbol A/d

    Test B1D3L/D= 2

    w (Hz) 3.0

    Normalized Deflection, y/d

    -10.0

    -5.0

    0.0

    5.0

    10.0

    -0.4 -0.2 0 0.2 0.4

    5 %10 %

    20 %50 %API

    Normalized Force , P/(s

    u.d.L)

    Symbol A/d

    Test B3D4L/D= 8

    w (Hz) 3.0

    Normalized Deflection, y/d

  • MULTIDIRECTIONAL P-Y ELEMENTS

  • Numerical Tool

    OpenSees

    Platform

    * Nonlinear Site

    Response (2-D)

    * Near Field, p-y

    Near Field, t-z andQ-z Capabilities

    New Elements

  • CONCLUSIONS- DEJA VU Key components are: (foundation) soil, foundation system &

    structure.

    Key issue of Performance Based Design is the evaluation(estimation) of performance -> Requirement of robust, efficient &realistic numerical- analytical description of material response &system.

    Development & refinement of laboratory experiments which canaccurately represent the problem are essential to validateindividual constructs (numerical/conceptual blocks). It thereforeprovides an invaluable resource for calibrating numerical Codes->Reduce inherent modeling uncertainty.

    Successful development of coupled site response and Soil-Pile-Superstructure Interaction analyses provides a Comprehensiveframework for Performance Based Design for increasingly highershaking levels