soil pile group interaction in fb-multipier
DESCRIPTION
Soil Pile Group Interaction in FB-MultiPier. Dr. J. Brian Anderson, P.E. Developed by: Florida Bridge Software Institute. Session Goals. Soil-Pile Group Interaction Discussion of Soil Strucuture Interaction Model Lateral p-y multipliers Axial efficiency factors - PowerPoint PPT PresentationTRANSCRIPT
Soil Pile Group Interaction in FB-MultiPier
Dr. J. Brian Anderson, P.E.
Developed by: Florida Bridge Software Institute
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
Coupled Soil-Structure Interaction
Ship Impact
Debris Impact
ScourPlumb Piles/Shafts
EarthquakeBattered Piles
Scour
Live and Dead Loading
Typical Deep Foundations:
Soil-Structure Interaction
Vertical Nonlinear SpringVertical Nonlinear Spring
Lateral Nonlinear SpringLateral Nonlinear Spring
Torsional Nonlinear Spring
Nonlinear Tip SpringNonlinear Tip Spring
Single Pile Model
P(F/L)
Y
Y
P(F/L)
Y
P(F/L)
(F/L2)
Z
(F/L2)
Z
(F/L2)
Z
Y
Z
Lateral Soil-Structure Interaction
Passive StateActive State
2
0
r dr)L/F(P
Y
P
Y
Soil-Pile Group Interaction
Lead Row
Smallest
Disturbance
Soil-Pile Group Interaction
Group Interaction:
Modeled with Multipliers
P-y curves
P x Pm1
P
P-y curves
P x Pm2
P
StaticShip Load
R R RI II III
BROWN & REESE (1988)
- Multipliers, Pm for P Values in P-y Curves
- Function of Row Position in Group
ROW Pm
R 0.8
R 0.4
R 0.3
I
II
III
Pm would be 0.3 for R or greaterIV
Soil-Pile Group Interaction - Lateral
P-Multipliers
• Axial Efficiency
Soil-Pile Group Interaction - Axial
Summing Effects of a Friction Pile Group (FHWA)
• Axial Efficiency
Soil-Pile Group Interaction - Axial
Block Failure Mode of Piles in Cohesive Soils
(FHWA)
Experiments
• Scale Cenrtifuge Models (UF)– Plumb and battered pile groups– Embedded caps
• Full Scale– Roosevelt Bridge Lateral Load Test (UF)– Axial Group Study (UH)
Centrifuge Modeling
50 ft
1 ft
50 g
Same Soil Stresses
Field Centrifuge
Full Scale Load Test at Roosevelt Bridge
Roosevelt 4x4 Field Study
Prediction of Field Response
DEFLECTION (IN)
0 1 2 3 4 5 60
200
400
600
800
1000
1200
LOAD-DEFLECTION CURVEROOSEVELT BRIDGE - TEST PILE GROUP
LOA
D (
KIP
S)
TEST PILE GROUP (MEASURED) FB-PIER PREDICTION
Single vs. Group Axial Behavior
3D
3D
10.75” pipe
25 ft
18 ft
clay
Sandy clay
FHWA: Houston
Study
Individual Group Axial Single AxialTotal Group
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
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
Pinned Laterally Loaded Pile Group
No VerticalMovement
Moment Shear Axial
Fixed Head Laterally Loaded Group
Axial ForcesMoment Shear
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
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
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