1. Caltrans Guidelines on Foundation Loading Due to Liquefaction Induced Lateral Spreading
Tom Shantz, Caltrans
2010 PEER Annual Meeting

2. Project Participants and Organization
PEER
Guidelines
Scott Ashford (OSU)
Ross Boulanger (UCD)
Scott Brandenberg (UCLA)
PEER TEAM
CALTRANS TEAM
Tom Shantz
Internal Review Team
Project Participants and Organization
Caltrans
Guidelines

3. Lessons from history…. Showa Bridge, Niigata (1964)
Source: ce.washington.edu
Showa Bridge, Niigata (1964)

4. Nishinomiya-ko bridge, Kobe (1995)

5. Photo by Yashinsky
Puente Tubul, Chile (2010)

6. Shukugawa Bridge, Kobe (1995)
Better performance…
Shukugawa Bridge, Kobe (1995)

7. Heisei Bridge, Sabaichi River, Niigata (2007)
Better performance…
Photos by Yashinsky
Heisei Bridge, Sabaichi River, Niigata (2007)

8. Kaiun Bridge, Sabaichi River, Niigata (2007)
Better performance…
Photos by Yashinsky
Kaiun Bridge, Sabaichi River, Niigata (2007)

9. Rinko Yasaka Bridge, Ugawa River, Niigata (2007)
Better performance…
Photos by Yashinsky
Rinko Yasaka Bridge, Ugawa River, Niigata (2007)

10. Caltrans’ current practice per Memo to Designer 20-15.
0.67 PULT
Crust
Liquefied
Dense
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

11. Issues the Guidelines Team sought to address…
Liquefiable Soil
Fill
Dense Soil
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

12. The team must confront challenging issues…
Pile pinning effect
Crust – pile cap
interaction
Residual strength
Static vs. dynamic loading
Estimation of crust
displacement
Kinematic and inertial
load combination

13. Strategy: Where possible, rely on test results.
NIED Shake Table: Elgamal (2003)
UC Davis centrifuge: Boulanger, Chang, Brandenberg, Armstrong,
and Kutter (2006)

14. Field testing…
Port of Takachi Tests by Ashford (2002)

15. + + Extend test results with numerical modeling…
Fill in gaps with judgment… + +

16. Caltrans Guidelines Limitations Software Options
“Since every project has unique aspects, these guidelines should not be used to constrain or replace engineering judgment.”
Software Options
Nonlinear moment-stiffness behavior: xSECTION, XTRACT, LPILE 5, others…
Soil-foundation interaction: LPILE 5, wFRAME, SAP2000
Slope stability: most commercial codes – no special requirements

17. Caltrans Guidelines Two design cases considered…
Liquefiable Soil
Fill
Dense Soil
Foundation restrained ground displacement
Unrestrained ground displacement

18. Caltrans Guidelines Unrestrained ground displacement case:
mp = N N2
Equivalent Nonlinear Static Analysis Approach
Crust loads applied through imposed soil displacement profile 1 3
fdepth
(Zc –D)/T
fwidth 14
WT/T
Fult based on log-spiral solution
Adjustment for wedge effect by Ovensen (1964). Kw ~ 1.3
pgroup =(psingle)(Npiles)(mp) or
pgroup =(psoft clay)(Npiles)
pgroup =(psingle)(Npiles)(GRF)
Matlock
Matlock (74) soft clay p-y model with Su = Sres and e50 = 0.05
LPILE 5 is limited to a single pile analysis

19. Caltrans Guidelines Unrestrained ground displacement case:
Equivalent Nonlinear Static Analysis Approach
Pile stiffness
Linear case:
EIgroup =(EIsingle)(Npiles)
Nonlinear case:
(See plot…)
Crust loads applied through imposed soil displacement profile fa fy
Mmax
(fa,Ma)
Ma = 1.1 Mmax
fa= 12 fy
Curvature
Moment
Stiffness (EI)
LPILE 5 is limited to a single pile analysis

20. Caltrans Guidelines Unrestrained ground displacement case: xi Kax, ni
Equivalent Nonlinear Static Analysis Approach
Crust loads applied through imposed soil displacement profile
Kax, ni xi
Class 100 pile: Kax = 0.75 (400 kips) / 0.25 in = 1200 kips/in
LPILE 5 is limited to a single pile analysis

21. Caltrans Guidelines Unrestrained ground displacement case:
Equivalent Nonlinear Static Analysis Approach
Crust loads applied through imposed soil displacement profile H V Mo
Vi =
Inertial Loads
Mi =Mo (LPILE 5: Mi
Abutment Case: assume inertial loads are zero
Fcapi=0.65 PGA mcap
0 )
LPILE 5 is limited to a single pile analysis

22. Caltrans Guidelines Unrestrained ground displacement case:
Equivalent Nonlinear Static Analysis Approach
Combination of kinematic and inertial loading
Combination of kinematic and inertial loading
Crust loads applied through imposed soil displacement profile
LPILE 5 is limited to a single pile analysis

23. Caltrans Guidelines Performance Criteria Ma Cap Displacement
Pile Moment
Pile Shear
Well confined pilings
H/20 Ma
SDC 3.6
Well confined abutment pilings
12 inches
Poorly confined pilings
2 inches -
*H = column height

24. Caltrans Guidelines Guideline availability and adoption:
The 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