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

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Presentation on theme: "Caltrans Guidelines on Foundation Loading Due to Liquefaction Induced Lateral Spreading Tom Shantz, Caltrans 2010 PEER Annual Meeting."— Presentation transcript:

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

2 PEER 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

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

4 Nishinomiya-ko bridge, Kobe (1995)

5 Puente Tubul, Chile (2010) Photo by Yashinsky

6 Shukugawa Bridge, Kobe (1995) Better performance…

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

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

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

10 Caltrans’ 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

11 Liquefiable 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

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

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

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

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

16 Caltrans 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

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

18 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: F ult based on log-spiral solution Adjustment for wedge effect by Ovensen (1964). K w ~ 1.3 1 0 03 f depth (Z c –D)/T f width 1 0 014W 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  50 = 0.05

19 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: Pile stiffness Linear case: EI group =(EI single )(N piles ) Nonlinear case: (See plot…) aa yy M max (  a,M a ) M a = 1.1 M max  a = 12  y Curvature Moment Stiffness (EI)

20 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: K ax, n i xixi Class 100 pile: K ax = 0.75 (400 kips) / 0.25 in = 1200 kips/in

21 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: H VMoMo V i = MoMo 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 )

22 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: Combination of kinematic and inertial loading

23 Cap DisplacementPile MomentPile Shear Well confined pilings H/20 MaMa SDC 3.6 Well confined abutment pilings 12 inches MaMa SDC 3.6 Poorly confined pilings 2 inches -- *H = column height Performance Criteria Caltrans Guidelines

24 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 tom.shantz@dot.ca.gov Caltrans Guidelines Guideline availability and adoption:


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