Loading Due to Liquefaction Induced Lateral Spreading Tom Shantz Caltrans 2010 PEER Annual Meeting PEER Guidelines Scott Ashford OSU Ross Boulanger UCD Scott Brandenberg UCLA ID: 807500
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Slide1
Caltrans Guidelines on Foundation
Loading Due to Liquefaction Induced Lateral Spreading
Tom Shantz, Caltrans
2010 PEER
Annual Meeting
Slide2PEER
Guidelines
Scott Ashford (OSU)
Ross Boulanger (UCD)
Scott
Brandenberg
(UCLA)
PEER TEAM
CALTRANS TEAM
Tom
Shantz
Internal Review Team
Caltrans
Guidelines
Project Participants and Organization
Slide3Showa Bridge, Niigata (1964)
Lessons from history….
Source: ce.washington.edu
Slide4N
ishinomiya-ko bridge, Kobe (1995)
Slide5Puente
Tubul, Chile (2010)
Photo by Yashinsky
Slide6Shukugawa
Bridge, Kobe (1995)
Better performance…
Slide7Heisei Bridge,
Sabaichi
River, Niigata (2007)
Better performance…
Photos by
Yashinsky
Slide8Kaiun Bridge,
Sabaichi
River, Niigata (2007)
Better performance…
Photos by
Yashinsky
Slide9Rinko
Yasaka Bridge, Ugawa River, Niigata (2007)
Better performance…
Photos by
Yashinsky
Slide10Caltrans’ current practice per Memo to Designer 20-15.
0.67 P
ULT
Liquefied
Dense
Crust
liquefied soil modeled as factored p-y curves (0.10 p-multiplier)
67% of the ultimate passive crust load is applied to the cap
no inertial loads are considered
performance criteria:
piles remain elastic
Slide11Liquefiable Soil
Fill
Dense Soil
Issues the Guidelines Team sought to address…
Crust load–deformation behavior. How much deformation to reach ultimate passive pressure? Adjustments for non-plane strain behavior.
Prediction of crust displacement.
Potential restraining effect of the foundation.
Potential restraining effect of the superstructure.
Contribution of inertial loads to the foundation displacement demand.
More specific performance criteria
Slide12Static vs. dynamic loading
Estimation of crust
displacement
Residual strength
Kinematic and inertial
load combinationCrust – pile cap interactionPile pinning effect
The team must confront challenging issues…
Slide13NIED Shake Table:
Elgamal (2003)
Strategy: Where possible, rely on test results.
UC Davis centrifuge: Boulanger, Chang,
Brandenberg
, Armstrong, and Kutter (2006)
Slide14Port of
Takachi
Tests by Ashford (2002)
Field testing…
Slide15Extend test results with
numerical modeling…
Fill in gaps with judgment…
+
+
Slide16Caltrans Guidelines
Software Options
Limitations
“Since every project has unique aspects, these guidelines should not be used to constrain or replace engineering judgment.”
Nonlinear moment-stiffness behavior: xSECTION, XTRACT, LPILE 5, others… Soil-foundation interaction: LPILE 5, wFRAME, SAP2000
Slope stability: most commercial codes – no special requirements
Slide17Liquefiable Soil
Fill
Dense Soil
Two design cases considered…
Unrestrained
ground displacement
Foundation restrained
ground displacement
Caltrans Guidelines
Slide18Equivalent Nonlinear Static Analysis Approach
LPILE 5 is limited to a single pile analysis
Crust loads applied through imposed soil displacement profile
Caltrans Guidelines
Unrestrained ground displacement case:
F
ult
based on log-spiral solution
Adjustment for wedge effect by
Ovensen
(1964).
K
w
~ 1.3
1
0
0
3
f
depth
(
Z
c
–D)/T
f
width
1
0
0
14
W
T
/T
p
group
=(
p
single
)(
N
piles
)(GRF)
p
group
=(
p
single
)(
N
piles
)(m
p
) or
p
group
=(
p
soft
clay
)(
N
piles
)
m
p
= 0.0031N + 0.00034N
2
Matlock
Matlock (74) soft clay p-y model with S
u
=
S
res
and
e
50
= 0.05
Slide19Equivalent Nonlinear Static Analysis Approach
LPILE 5 is limited to a single pile analysis
Crust loads applied through imposed soil displacement profile
Caltrans Guidelines
Unrestrained ground displacement case:
Pile stiffness
Linear case:
EI
group
=(
EI
single
)(
N
piles
)
Nonlinear case:(See plot…)
fa
fy
M
max
(
f
a
,M
a
)
M
a
= 1.1
M
max
f
a
= 12
f
y
Curvature
Moment
Moment
Stiffness (EI)
Slide20Equivalent Nonlinear Static Analysis Approach
LPILE 5 is limited to a single pile analysis
Crust loads applied through imposed soil displacement profile
Caltrans Guidelines
Unrestrained ground displacement case:
K
ax
,
n
i
x
i
Class 100 pile:
K
ax
= 0.75 (400 kips) / 0.25 in = 1200 kips/in
Slide21Equivalent Nonlinear Static Analysis Approach
LPILE 5 is limited to a single pile analysis
Crust loads applied through imposed soil displacement profile
Caltrans Guidelines
Unrestrained ground displacement case:
H
V
M
o
V
i
=
M
o
H
Inertial Loads
M
i
=
M
o
(LPILE 5: M
i
Abutment Case:
assume inertial loads
are zero
F
cap
i
=0.65 PGA
m
cap
0 )
Slide22Equivalent Nonlinear Static Analysis Approach
LPILE 5 is limited to a single pile analysis
Crust loads applied through imposed soil displacement profile
Caltrans Guidelines
Unrestrained ground displacement case:
Combination of kinematic and inertial loading
Combination of kinematic and inertial loading
Slide23Cap Displacement
Pile Moment
Pile Shear
Well confined pilings
H/20
M
a
SDC 3.6
Well confined abutment pilings
12 inches
M
a
SDC 3.6
Poorly confined pilings
2 inches
-
-
*H = column height
Performance
Criteria
Caltrans Guidelines
Slide24The new guidelines will be available on the Geotechnical Services and Office of Earthquake Engineering websites
Guidelines official adoption date has not yet been determined.Any questions or concerns, or you can’t find the guidelines, contact me at tom.shantz@dot.ca.gov
Caltrans Guidelines
Guideline availability and adoption: