Youssef Hashash In collaboration with Duhee Park 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

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 Features of DEEPSOIL Nonlinear Numerical Model User Interface Equivalent Linear Additional Features of the User Interface

Nonlinear (NL) Features Soil Model Viscous Damping Formulation Dynamic Integration Scheme Increased Numerical Accuracy User Interface

NL Feature – Soil Model Extended Modified Hyperbolic Model Based on Modified Hyperbolic Model (Matasovic, 1993) Confining pressure dependent Modified Hyperbolic Model

NL Feature – Soil Model G / Gmax & Confinement Damping & Confinement

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 Formulation Target Damping Ratio Fig 3-1 Page 68

Feature 2 – Viscous Damping Formulation Target Damping Ratio 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

NL Feature– Viscous Damping Formulation Target Damping Ratio

Numerical Implementation Cyclic soil response model Input ground motion Multi-degree of freedom lumped parameter model

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 Formulation RF – Conventional Approach Use first mode of soil column and a higher mode or predominant period of ground motion

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 Formulation Variable [C] Matrix Updates stiffness in the RF formulation

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 – Input Soil Profile

NL User Interface – Input Soil Profile

NL User Interface – Soil Model Parameter Selection

NL User Interface – Viscous Damping Formulation ME Profile M=8,R=32km Motion

NL User Interface – Viscous Damping Formulation

NL User Interface – Viscous Damping Formulation

NL User Interface – Viscous Damping Formulation

NL User Interface – Numerical Accuracy Control

NL User Interface – Output

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 (SHAKE, use with care)

Additional Features

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: ~88 m

Verification of DEEPSOIL E-W N-S

Nonlinear Soil Model Parameters No Fixed Parameter Selected to match various reference dynamic curves (G/Gmax and damping curves)

NL Soil Model Parameters – Mississippi Embayment (ME) ME study ME EPRI  1.4 0.85 s 0.8 0.9 (a) Reference strain @ ’ref 0.163 0.07 ’ref 0.18 b 0.63 0.4 c Varies with depth d

NL Soil Model Parameters - EPRI ME study ME EPRI  1.4 0.85 s 0.8 0.9 (a) Reference strain @ ’ref 0.163 0.07 ’ref 0.18 b 0.63 0.4 c Varies with depth d

NL Soil Model Parameters-Treasure Island Young Bay Mud Old Bay Mud  0.8 0.9 s 0.7 (a) Reference strain @ ’ref 0.17 0.065 ’ref N/A b 0.0 c 1.5 d

NL Soil Model Parameters-Anchorage Bootlegger clay  0.7 s Reference strain 0.05 ’ref N/A b 0.0 c 1.0 d

Limitations No Pore pressure generation model Currently under development Implementation of a NN based constitutive model

Questions?

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