4_SHANTZ

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Caltrans Guidelines on Foundation Loading Due

to Liquefaction Induced Lateral Spreading

Tom Shantz, Caltrans

January 28, 2011 NACGEA Workshop

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PEER

GuidelinesScott Ashford (OSU)

Ross Boulanger (UCD)Scott Brandenberg (UCLA)

PEER TEAM

CALTRANS TEAMTom Shantz

Internal Review Team

Caltrans

Guidelines

Project

Participantsand

Organization

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Showa Bridge, Niigata (1964)

Lessons from history….

Source: ce.washington.edu

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Nishinomiya-ko bridge,

Kobe (1995)

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Puente Tubul, Chile (2010)Photo by Yashinsky

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Shukugawa Bridge, Kobe (1995)

Better performance…

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Heisei Bridge, Sabaichi River, Niigata (2007)


Photos by Yashinsky

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Kaiun Bridge, Sabaichi River, Niigata (2007)


Photos by Yashinsky

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Rinko Yasaka Bridge, Ugawa River, Niigata (2007)


Photos by Yashinsky

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Caltrans’ current practice per Memo to Designer 20-15.

0.67 PULT

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

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Liquefiable Soil

Fill

Dense Soil

Issues the Guidelines Team sought to address…

•

Crust load–deformation behavior. How much deformation to reachultimate 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.

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Static vs. dynamic loadingEstimation of crust

displacement

Residual strength

Kinematic and inertial

load combination

Crust – pile cap

interaction

Pile pinning effect

The team must confront challenging issues…

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NIED Shake Table: Elgamal (2003)

Strategy: Where possible, rely on test results.

UC Davis centrifuge: Boulanger, Chang, Brandenberg, Armstrong,

and Kutter (2006)

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Port of Takachi Tests by Ashford (2002)

Field testing…

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Extend test results with numerical modeling…

Fill in gaps with judgment…

+ +

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Liquefiable Soil

Fill

Dense Soil

Two design cases considered…

Unrestrained ground displacement

Foundation restrained

ground displacement

Caltrans Guidelines

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Equivalent 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:

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1

00 3(Zc –D)/T

1

00 14WT/T

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Adjustment for wedge effect

by Ovensen (1964). Kw ~ 1.3

Crust

Liquefied

Sand

Rankine

Passive

Crust

Liquefied

Sand

Log-spiral

Passive

Case A Case B

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Caltrans Guidelines


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φaφy

Mmax (φa,Ma)

Ma = 1.1 Mmax

φa

= 12 φy

Curvature

M

o m e n t

Moment

S t i f f n e s s ( E I )

Pile stiffnessLinear case:

EIgroup =(EIsingle)(Npiles)Nonlinear case:

(See plot…)

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Caltrans Guidelines


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Kax, ni

xi

K M 144K ax ni xi2

Class 100 pile: Kax = 0.75 (400 kips) / 0.25 in = 1200 kips/in

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orH

VM

o

Vi =(1 or 2) x Mo

H

Inertial Loads

Mi =Mo (LPILE 5: Mi

Abutment Case: assume inertial loads are zero

Fcapi=0.65 PGA mcap

0 )

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Combination of kinematic and inertial loading

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Cap Displacement Pile Moment Pile Shear

Well confined

pilings

H/20 MaSDC 3.6

Well confined

abutment pilings

12 inches MaSDC 3.6

Poorly confined

pilings

2 inches - -

*H = column

height

Performance Criteria

Caltrans Guidelines

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Two methods of estimating ground displacement…

Strain potential approach Newmark approach

Caltrans Guidelines

Caltrans Guidelines

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Strain potential approach - hybrid of Faris (2004) and Zhang (2004)

Caltrans Guidelines

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Adjustment for near-flat conditions

S = ground slope

L

HH’ max = Hmax . F amp F amp = 6 (L/H)-0.8 for 4 < L/H < 9

2 for L/H < 4

1 for 9 < L/H

Adjustment for open face conditions

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Caltrans Guidelines

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Foundation restrained ground displacement design case:

Liquefiable Soil

Fill

Dense Soil

Failure Surface

R

F s

Ky R (k/ft) D (in)

0.087 0 7.8

0.1 7 6.1

0.13 21 3.7

0.16 36 2.4

0.19 52 1.7

Caltrans Guidelines

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H

4H (max)

Displacement

R e s i s t a n c e ( R )

(1)

(2)

(3)

Disp (in)

Shear

(kips)

0 0

1 338

2 6594 1220

6 1540

8 1680

10 1750

Disp (in)

Shear

(kips)

Avg

(kips)

0 0 0

1 338 169

2 659 3324 1220 554

6 1540 751

8 1680 906

10 1750 1027

Equivalent constant shear

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Cap Displacement Pile Moment Pile Shear

Well confined

pilings

H/20 MaSDC 3.6

Well confined

abutment pilings

12 inches MaSDC 3.6

Poorly confined

pilings

2 inches - -

*H = column

height

Performance Criteria

Caltrans Guidelines

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The new guidelines are available on ARS Online website Technical

References Link (http://dap3.dot.ca.gov/shake_stable/)

Any questions or concerns, or you can’t find the guidelines, contact me

at [email protected]

Caltrans Guidelines

Guideline availability:

http://dap3.dot.ca.gov/shake_stable/

http://dap3.dot.ca.gov/shake_stable/

4_SHANTZ

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