Geotechnical Seismic Simulation

1
Geotechnical Seismic Simulation
PEER 2002 Annual Meeting

• Ahmed Elgamal
• UCSD

Vision Professor Steven Kramer (PEER
Geotechnical Thrust Area Leader)
2
Humboldt Bay, Middle Channel Bridge
Selected in Collaboration with Caltrans
Recently Pat Hipley Keith Porter (PEER) Cliff
Roblee Tom Shantz Mark Yashinsky

• 330 meters long, 9-span built in 1972 (seismic
  retrofit in 95 00)
• Supported on piles in soft soil vulnerable to
  liquefaction
• Near active seismic zone with reverse faulting
  mechanism
• Instrumented including nearby downhole array

3
Project Goals

• Develop a bridge seismic assessment framework
  based on computational modeling and sound
  probabilistic analysis
• Ultimately, a Decision Making Tool
• Estimate Maintenance/repair expenses
• Estimate down-time/reduced capacity
• Explore Retrofit scenarios
• Predict Emergency shutdown scenarios

4
Maintenance/repair cost
5
Down-time Lane closure.Emergency Shutdown
Professor Joel Conte
(e.g., repair cost or loss of functionality)
6
OpenSees Professor Greg Fenves
Dr. Frank McKenna
Finite Element Model
Water Table

• Mesh generated using GID ( http//gid.cimne.upc.e
  s
• Prof. Pedro Arduino
• http//ce.washington.edu/geotech/opensees/)

Dr. Zhaohui Yang, Prof. Joel Conte
Abutments Structural Joints Liquefaction
SSI
7

• Abutment Joints ZeroLength Element with
  Gap-Hook Material

Prof. Joel Conte
8
Soil Constitutive Model

• Pressure-dependent multi-surface plasticity model
  (for gravel, sand, and silt), incorporating
  liquefaction effects

Dr. Zhaohui Yang
9
UC Berkeley Shear Tests Pestana, Seed, and
Kammerer
10
SSI
Prof. Ross Boulanger
Comparison of Matlocks (1970) test on soft clay
and PySimple1 with the same loading path.
11
Yang, Conte, Zhang
12
Simulation of UC Davis Centrifuge Test
Kutter, Boulanger, Idriss, and Wilson
13
Current Research Seismic Hazard Analysis
Dr. Paul Somerville
Site Specific Eq. motions at 3 Hazard Levels
(50, 10, and 2)
Middle Channel Bridge
J. Conte
14
Current Research Spatial Definition of Input
Excitation
Lateral Boundaries, Base of the Mesh,
Transmitting boundary, Wave propagation
Plastic Bowl Method Prof. Jacobo Bielak/Prof.
Boris Jeremic
SCEC
15
3D 2D Mesh, Piles, and Abutments
4x3 pile model
Plastic zone
Professor Boris Jeremic
16
OpenSees
100 years too late for this Bridge, But just
in time for Humboldt Bay.
UC Berkeley Photo Database