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Youssef Hashash Associate Professor In collaboration with Duhee Park Post-Doctoral Research Assistant University of Ill

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Youssef Hashash Associate Professor In collaboration with Duhee Park Post-Doctoral Research Assistant University of Illinois at Urbana-Champaign PEER 2G02 First Meeting September 21, 2004. DEEPSOIL. 1-D Site response analysis code Nonlinear / Equivalent linear analysis User interface.

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slide1

Youssef Hashash

Associate Professor

In collaboration with Duhee Park

Post-Doctoral Research Assistant

University of Illinois at Urbana-Champaign

PEER 2G02 First Meeting

September 21, 2004

deepsoil
DEEPSOIL
  • 1-D Site response analysis code
  • Nonlinear / Equivalent linear analysis
  • User interface
motivation for development
Motivation for Development
  • Thick soil deposits such as those encountered in the Mississippi Embayment in Mid-America
  • Sponsored in part by Mid-America Earthquake Center
  • References:
    • Park, D. and Y. M. A. Hashash (2004). "Soil damping formulation in nonlinear time domain site response analysis." Journal of Earthquake Engineering 8(2): 249-274.
    • Hashash, Y. M. A., and Park, D. (2002). "Viscous damping formulation and high frequency motion propagation in nonlinear site response analysis." Soil Dynamics and Earthquake Engineering, 22(7), pp. 611-624.
    • Hashash, Y. M. A., and Park, D. (2001). "Non-linear one-dimensional seismic ground motion propagation in the Mississippi embayment." Engineering Geology, 62(1-3), 185-206.
    • Park, D. (2003). ESTIMATION OF NON-LINEAR SEISMIC SITE EFFECTS FOR DEEP DEPOSITS OF THE MISSISSIPPI EMBAYMENT. Department of Civil and Environmental Engineering. Urbana, University of Illinois at Urbana-Champaign: 337 p.
outline
Outline
  • Features of DEEPSOIL
    • Nonlinear
      • Numerical Model
      • User Interface
    • Equivalent Linear
      • Numerical Model
      • User Interface
    • Additional Features of the User Interface
nonlinear nl features
Nonlinear (NL) Features
  • Soil Model
  • Viscous Damping Formulation
  • Dynamic Integration Scheme
  • Increased Numerical Accuracy
  • User Interface
nl feature soil model
NL Feature – Soil Model
  • Extended Modified Hyperbolic Model
    • Based on Modified Hyperbolic Model (Matasovic, 1993)
    • Confining pressure dependent

Modified Hyperbolic Model

nl feature soil model7

Damping

& Confinement

NL Feature – Soil Model

G / Gmax

& Confinement

nl feature viscous damping formulation
NL Feature– Viscous Damping Formulation
  • Viscous damping formulation [C]
  • Simplified Rayleigh damping formulation
  • Full Rayleigh damping formulation

Conventional Selection of Frequencies/Modes (CRF)

Proposed Selection (RF)

  • Extended Rayleigh damping formulation (ERF)
feature 2 viscous damping formulation10

Target Damping Ratio

Feature 2 – Viscous Damping Formulation

Selection of frequencies/modes for Full Rayleigh damping formulation

CRF (Conventional RF) : fm = 1st mode of soil column, fn=dominant period of input motion

RF (Proposed RF) : fm and fn chosen from transfer function of soil column and frequency content of

input motion  An iterative process

numerical implementation
Numerical Implementation

Cyclic soil response model

Input ground motion

Multi-degree of freedom

lumped parameter model

nonlinear nl integration scheme
Nonlinear (NL) Integration Scheme
  • Newmark Beta Method

(Average acceleration method: =1/4, =1/2

    • Implicit Method
    • Unconditionally stable
    • No numerical damping
nl feature viscous damping formulation14
NL Feature – Viscous Damping Formulation
  • RF – Conventional Approach
    • Use first mode of soil column and

a higher mode or predominant

period of ground motion

nl feature viscous damping formulation15
NL Feature – Viscous Damping Formulation
  • RF/ERF

Proposed Guideline

    • Use iterative procedure to obtain best match with frequency domain solution
    • Dependent on soil column
    • Dependent on input motion
    • ERF: Computationally expensive
nl feature viscous damping formulation16
NL Feature – Viscous Damping Formulation
  • Variable [C] Matrix
    • Updates stiffness in the RF formulation
nl feature increased numerical accuracy
NL Feature – Increased Numerical Accuracy

Fixed Sub-incrementation Scheme: Independent of strain level

Flexible Sub-incrementation Scheme: depends on strain level

Input Motion

Station JMA NS Kobe Earthquake, PGA = 0.82g

nl user interface viscous damping formulation
NL User Interface – Viscous Damping Formulation

300 m

ME Profile

M=8,R=32km Motion

equivalent linear eql features
Equivalent linear (EQL) Features
  • 3 Types of Complex shear modulus
    • Frequency independent (Kramer, 1996)
    • Frequency dependent (Udaka, 1975)
    • Simplified (Kramer, 1996)
  • No limitation on
    • number of layers
    • number of materials
    • number of motion data points
eql features
EQL Features

(SHAKE, use with care)

verification of deepsoil
Verification of DEEPSOIL
  • Loma Prieta Earthquake, M = 7.1, October 19, 1989
  • Significance of viscous damping in DEEPSOIL (Strong Motion & non-linear material)
  • Soil column: ~88m
nonlinear soil model parameters
Nonlinear Soil Model Parameters
  • No Fixed Parameter
  • Selected to match various reference dynamic curves (G/Gmax and damping curves)
limitations
Limitations
  • No Pore pressure generation model
    • Currently under development
  • Implementation of a NN based constitutive model