PEER%202G02%20

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PEER 2G02 Code Usage Exercise
OpenSees Zhaohui Yang UCSD 2/15/2005
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Treasure Island site
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• Total model height 100 m (328 ft)
• Discretized into 106 elements
• Lysmer transmitting boundary with incident
  motion specified as ½ of the outcropping motion
  given

Model base
Elastic half space
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• G/Gmax and damping curves
• Fitted MD/damping curves (blue) were used at
  UCLA
• Measured MR curves (red) were used at UCSD, with
  higher damping

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Rayleigh damping employed Damping ratio 1 at
1 Hz and 6 Hz (as measured damping ratio at low
strain is about 1)
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Computed acceleration Time Histories (UCSD)
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Response Spectrum (5 damping)
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• Comments on response spectrum
• All analyses give similar spectrum shapes.
• Compared to rock outcropping motion, response at
  soil surface is amplified for period gt 0.25 sec
  and de-amplified for period lt 0.25 sec.
• Nonlinear analysis results are much lower than
  that of SHAKE at period 0.6-2 sec, due to strong
  nonlinearity at this soft soil site.
• UCLA response is generally higher than that of
  UCSD, due to lower damping curves used at UCLA.

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• Profile of maximum shear strain (UCSD)
• approximately in proportion to shear wave
  velocity (Gmax) profile, as lower Gmax -gt lower
  backbone curve -gt more nonlinearity -gt higher
  shear strain

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Permanent displacement profile after shaking
(UCSD) (strong correlation with shear wave
velocity (Gmax) profile)
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• Location with strongest shear stress-strain
  response (UCSD)
• Notice permanent shear strain incurred in a
  single pulse

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Shear stress-strain response at base (UCSD)
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Shear stress-strain response near surface (UCSD)
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Gilroy site
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• Total model height 170.7 m (560 ft)
• Discretized into 173 elements
• Lysmer transmitting boundary with incident
  motion specified as ½ of the outcropping motion
  given

Model base
Elastic half space
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• G/Gmax and damping curves
• Fitted MD/damping curves (blue) were used at
  UCLA
• Measured MR curves (red) were used at UCSD, with
  higher damping

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• G/Gmax and damping curves
• Fitted MD/damping curves (blue) were used at
  UCLA
• Measured MR curves (red) were used at UCSD, with
  higher damping

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• Rayleigh damping employed
• UCSD Damping ratio 3 at 1 Hz and 6 Hz (as
  measured damping ratio at low strain is about 3)
• UCLA Damping ratio 1 at 1 Hz and 6 Hz

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Computed Acceleration Time Histories (UCSD)
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Response Spectrum (5 damping) Significant
surface amplification at 0.13-2 second periods
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• Comments on response spectrum
• All analyses give similar spectrum shapes.
• Compared to rock outcropping motion, response at
  soil surface is amplified for period gt 0.13 sec
  and de-amplified for period lt 0.13 sec.
• Nonlinear analysis results are similar to that
  of SHAKE, as this site is more competent (less
  nonlinearity).
• UCLA response is generally higher than that of
  UCSD, due to lower damping curves used at UCLA.

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• Profile of maximum shear strain (UCSD)
• Strong correlation with shear wave velocity
  (Gmax) profile.

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Permanent displacement profile after shaking
(UCSD)
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Location with maximum shear stress-strain
response (UCSD)
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Shear stress-strain response at base (UCSD)
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Shear stress-strain response at surface (UCSD)
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Influence of Rayleigh damping on surface
acceleration