Bridge%20Pier%20Analysis%20and%20Design

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Soil Pile Group Interaction in FB-MultiPier
Dr. J. Brian Anderson, P.E.
Developed by Florida Bridge Software Institute
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Session Goals

• Soil-Pile Group Interaction
• Discussion of Soil Strucuture Interaction Model
• Lateral p-y multipliers
• Axial efficiency factors
• Example 2 Pile Group Analysis Load Test at
  Roosevelt Bridge

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Coupled Soil-Structure Interaction
Ship Impact
4
Typical Deep Foundations
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Soil-Structure Interaction
Vertical Nonlinear Spring
Torsional Nonlinear Spring
Lateral Nonlinear Spring
Nonlinear Tip Spring
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Single Pile Model
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Lateral Soil-Structure Interaction
Y
Active State
Passive State
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Soil-Pile Group Interaction
Lead Row Smallest Disturbance
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Soil-Pile Group Interaction
P
P x Pm2
P-y curves
P
P x Pm1
P-y curves
Group Interaction Modeled with Multipliers
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Soil-Pile Group Interaction - Lateral
P-Multipliers
BROWN REESE (1988)
R
R
R
I
II
III
- Multipliers, Pm for P Values in P-y Curves
- Function of Row Position in Group
ROW Pm
R 0.8
I
R 0.4
II
Static
R 0.3
Ship Load
III
Pm would be 0.3 for R or greater
IV
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Soil-Pile Group Interaction - Axial

• Axial Efficiency

Summing Effects of a Friction Pile Group (FHWA)
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Soil-Pile Group Interaction - Axial

• Axial Efficiency

Block Failure Mode of Piles in Cohesive Soils
(FHWA)
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Experiments

• Scale Cenrtifuge Models (UF)
• Plumb and battered pile groups
• Embedded caps
• Full Scale
• Roosevelt Bridge Lateral Load Test (UF)
• Axial Group Study (UH)

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Centrifuge Modeling
Field
1 ft
Centrifuge
50 g
50 ft
Same Soil Stresses
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Full Scale Load Test at Roosevelt Bridge
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Roosevelt 4x4 Field Study
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Prediction of Field Response
DEFLECTION (IN)
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Single vs. Group Axial Behavior
FHWA Houston Study
25 ft
clay
18 ft
Sandy clay
Total Group
Individual Group Axial
Single Axial
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Experimental Results Plumb Piles

• Efficiencies and multipliers are independent of
  soil density
• Group Efficiencies
• At 5D Spacings - 95
• At 3D Spacings - 70 to 75
• Lateral Multipliers
• At 3D Spacing- 0.8, 0.4, 0.3, 0.2, 0.2,,0.3
• At 5D Spacing- 1.0 , 0.85, 0.7,..,0.7

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Experimental - Battered Piles

• Efficiencies and multipliers are independent of
  soil density
• Lateral Multipliers
• At 3D Spacing- 0.8, 0.4, 0.3, 0.2, 0.2,,0.3
• At 5D Spacing- 1.0 , 0.85, 0.7,..,0.7
• Data Available only for A frame design

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Pinned Laterally Loaded Pile Group
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Fixed Head Laterally Loaded Group
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Design Summary

• Pile Group response is strongly influenced by
  geometry, loading, connectivity, material
  characterization
• geometry 3D vs. 5D, battered vs. plumb
• connectivity fixed vs. pinned pile heads
• loading lateral or combined lateral axial
• material linear vs. nonlinear pile models

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References

• Zhang, L.M., McVay, M.C., Han, S.J., Lai, P. and
  Gardner, R., Effects of Dead Loads on the
  Lateral Response of Battered Pile Groups,
  Canadian Geotechnical Journal, Vol. 39, No. 6,
  June 2002, pg. 188-203.
• McVay, M.C., Zhang, L., Molnit, T., Bollmann, H.,
  and Lai, P., Centrifuge Testing of Large Plumb
  Pile Groups (3x3 To 7x3) in Sands, ASCE, Journal
  of Geotechnical Engineering, Oct. 1998, Vol. 124,
  No 10, pp. 1016-1026.
• Zhang, L., McVay, M.C., and Lai, P., Numerical
  Analysis of Fixed Head 3x3 to 7x3 Plumb Pile
  Groups in Sands, ASCE, Journal of Geotechnical
  Engineering, Nov, 1999, Vol. 125, No. 11, pp.
  936-946.
• Brown, D, Morrison, C., and Reese, L. Lateral
  Load Behavior of a Pile Group in Sand, ASCE,
  Journal of Geotechnical Engineering, 1988, Vol
  114, No. 11, pp. 1261-1276
• McVay, M.C., Zhang, L., Han, S., and Lai, P.,
  Experimental and Analytical Modeling of
  Laterally Loaded Pile Groups with Embedded Pile
  Caps in Sand, Transportation Research Record,
  No. 1736, Dec. 2000, pp. 12-18.
• Pinto, P. and McVay, M.C., Hoit, M., and Lai, P,
  Centrifuge Testing of Plumb and Battered Pile
  Groups in Sand, Transportation Research Record,
  No. 1569, Jan. 1997, pp. 8-16.
• O'Neill, M. W., Brown, D. A., Anderson, D. G., El
  Naggar, M. H., Townsend, F. C., Mcvay, M. C.
  (1997). Static and dynamic lateral loading of
  pile groups. NCHRP 24-9, Highway Research
  Center, Harbert Engineering Center, Auburn
  University, Auburn, AL

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Session Goals

• Soil-Pile Group Interaction
• Discussion of Soil Strucuture Interaction Model
• Lateral p-y multipliers
• Axial efficiency factors
• Example 2 Pile Group Analysis Load Test at
  Roosevelt Bridge