steve kramer university of washington seismic site response analysis eeri technical seminar series...
TRANSCRIPT
![Page 1: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/1.jpg)
Steve KramerUniversity of Washington
Seismic Site Response Analysis
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 2: Practical Applications to Deep Foundations
Soil-Structure Interaction:Basic Concepts
Steve Kramer
University of Washington
![Page 2: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/2.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 3: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/3.jpg)
Soil-Structure Interaction
How does the presence of soil affect the response of a structure?
Rock Rock
Soil
Does the structure founded on rock respond differently than when founded on soil?
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How does the presence of a structure affect the response of the soil?
Rock
Soil
Foundation input motion
Free-field motion
How does the motion at the base of the structure differ from the free-field motion?
Soil-Structure Interaction
![Page 5: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/5.jpg)
Soil-Structure Interaction
In reality, the response of the soil affects the response of the structure, and the response of the structure affects the response of the soil
Soil-Structure Interaction
Two components:
Inertial interaction
Inertial response of structure causes base shear and moments which cause displacements of foundation relative to free-field.
Kinematic interaction
Presence of stiff foundation elements on or in soil cause foundation motions to deviate from free-field motions.
![Page 6: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/6.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – variation of ground motion with depth
Wave scattering – scattering off corners and edges
Base slab averaging – stiffness of foundation prevents it from matching free-field deformations. Exists even for massless foundation.
![Page 7: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/7.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 8: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/8.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – variation of ground motion with depth
Wave scattering – scattering off corners and edges
Flexible pile
Deformation matches free-field deformation
Surface motion = free-field motion
No rotation at surface
![Page 9: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/9.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – variation of ground motion with depth
Wave scattering – scattering off corners and edges
Rigid pile
Deformation different than free-field deformation – can translate and rotate
Surface motion = free-field motion
Rotation and displacement at surface
![Page 10: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/10.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – reduction of ground motion with depth
Wave scattering – scattering off corners and edges
Ground motion amplitude decreases with depth
![Page 11: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/11.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – reduction of ground motion with depth
Wave scattering – scattering off corners and edges
Vertically propagating shear waves can cause rocking as well as translation
![Page 12: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/12.jpg)
Soil-Structure Interaction
Kinematic SSI has three primary causes:
Base slab averaging – results from stiffness of foundation
Embedment – reduction of ground motion with depth
Wave scattering – scattering off corners and edges
Wave scattering reduces amplitude of high frequency components
![Page 13: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/13.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 14: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/14.jpg)
Soil-Structure Interaction
Inertial SSI results from compliance of soil
Soil is not rigid – will deform due to loads from structure
Translation in three directions
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Soil-Structure Interaction
Inertial SSI results from compliance of soil
Soil is not rigid – will deform due to loads from structure
Rotation about three axes
z
y
x
z
y
x
z
y
x
z
y
x
u
u
u
kkkkkk
kkkkkk
kkkkkk
kkkkkk
kkkkkk
kkkkkk
M
M
M
F
F
F
666564636261
565554535251
464544434241
363534333231
262524232221
161514131211
6 x 6 stiffness matrix to describe foundation compliance
![Page 16: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/16.jpg)
Soil-Structure Interaction
Inertial SSI results from compliance of soil
Soil is not rigid – will deform due to loads from structure
Displacement in two directions
Rocking about one axis
z
y
x
z
y
x
u
u
kk
k
kk
M
F
F
3331
22
1311
0
00
0 3 x 3 stiffness matrix to describe foundation compliance
![Page 17: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/17.jpg)
Soil-Structure Interaction
Inertial SSI results from compliance of soil
Soil is not rigid – will deform due to loads from structure
Deformations resulting from structural forces will propagate away from structure
Energy “removed” from structure – radiation damping
![Page 18: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/18.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 19: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/19.jpg)
Soil-Structure Interaction
Analysis of soil-structure interaction
Two approaches
Direct approach – model soil and structure together
Requires detailed model of structure and soil in one computer program
Can handle nonlinear soil and structural response
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Soil-Structure Interaction
Analysis of soil-structure interaction
Two approaches
Direct approach – model soil and structure together
Substructure approach – model separately and combine
Kinematic SSI
Inertial SSI
Can use different codes for soil and structural response
Superposition requires linearity
![Page 21: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/21.jpg)
Soil-Structure Interaction
Analysis of kinematic soil-structure interaction
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Soil-Structure Interaction
Analysis of kinematic soil-structure interaction
Model foundation as massless but with actual stiffness
uFIM
qFIM
Compute foundation input motions, uFIM and qFIM
Influenced by stiffness and geometry of soil and foundation
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Soil-Structure Interaction
6 x 6 matrix of complex impedance coefficients
3 translational coefficients
3 rotational coefficients
Cross-coupling (off-diagonal) coefficients
Impedance function – foundation stiffness and damping
kvcv
Qv
khk
q
chc
q
MQh
Kv = kv + icvw
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Soil-Structure Interaction
Analysis of structure on compliant base subjected to FIM
kvcv
khk
q
chc
q
uFIM
qFIM
Based on principle of superposition – assumed linearity
Frequently performed using equivalent linear approach
![Page 25: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/25.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 26: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/26.jpg)
Soil-Structure Interaction
Effects of soil-structure interaction
Consider simplified model
SDOF system on compliant base
Horizontal translation
Rocking
SDOF system on compliant base
Horizontal translation
Rocking
Base of structure can translateand rotate
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Soil-Structure Interaction
Effects of soil-structure interaction
Consider simplified model
SDOF system on compliant base
Horizontal translation
Rocking
SDOF system on compliant base
Horizontal translation
Rocking
Displacement of ground Displacement
due to horizontal translation
Displacement due to rocking
Displacement due to distortion of structure
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Soil-Structure Interaction
Effects of soil-structure interaction
Consider simplified model
k
kh
k
k
T
T
u
2
1~
30)/
~(
~~
TT
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Soil-Structure Interaction
T/T~
h/(VsT)Stiff soilFlexible structure
Soft soilStiff structure
Period lengthening is negligible for a soft structure on stiff soil – it’s effects increase with increasing structure/soil relative stiffness.
SSI effects are small for flexible structure on stiff site, but significant for stiff structure on soft soil.
Period lengthening is negligible for a soft structure on stiff soil – it’s effects increase with increasing structure/soil relative stiffness.
SSI effects are small for flexible structure on stiff site, but significant for stiff structure on soft soil.
Structure on circular footing of radius, r
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Soil-Structure Interaction
h/(VsT)Stiff soilFlexible structure
Soft soilStiff structure
Radiation damping is negligible for a soft structure on stiff soil – it’s effects increase with increasing structure/soil relative stiffness.
Relative importance of radiation damping decreases with increasing h/r (increasing rocking response).
SSI effects are small for flexible structure on stiff site, but significant for stiff structure on soft soil.
Radiation damping is negligible for a soft structure on stiff soil – it’s effects increase with increasing structure/soil relative stiffness.
Relative importance of radiation damping decreases with increasing h/r (increasing rocking response).
SSI effects are small for flexible structure on stiff site, but significant for stiff structure on soft soil.
![Page 31: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/31.jpg)
Soil-Structure Interaction
Effects of soil-structure interaction
Consider simplified model
k
kh
k
k
T
T
u
2
1~
30)/
~(
~~
TT
With increasing foundation flexibility,
Period lengthens
Damping increases
With increasing foundation flexibility,
Period lengthens
Damping increases
SSI can decrease structural deformations, loads
![Page 32: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/32.jpg)
Soil-Structure Interaction
Effects of soil-structure interaction
Consider simplified model
k
kh
k
k
T
T
u
2
1~
30)/
~(
~~
TT
With increasing foundation flexibility,
Period lengthens
Damping increases
With increasing foundation flexibility,
Period lengthens
Damping increases
SSI can increase total displacements
![Page 33: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/33.jpg)
Soil-Structure Interaction Basics
Summary
SSI is not significant for cases of flexible structures on stiff soil deposits
SSI can be quite significant for stiff structures founded on soft soils
Fundamental period of soil-structure system is longer than that of fixed-base structure
Effective damping of soil-structure system is higher than damping of structure alone
Total displacements can be increased by SSI – can be important for closely-spaced tall structures
Neglecting SSI is equivalent to assuming the structure is supported on rigid materials
![Page 34: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/34.jpg)
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
Outline
![Page 35: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/35.jpg)
Why?
Poor soil conditions
Soft, weak, compressible
Deep Foundations
![Page 36: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/36.jpg)
Why?
Poor soil conditions
Soft, weak, compressible
Deep Foundations
![Page 37: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/37.jpg)
Why?
Poor soil conditions
Soft, weak, compressible
Deep Foundations
![Page 38: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/38.jpg)
Why?
Poor soil conditions
Soft, weak, compressible
Deep Foundations
![Page 39: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/39.jpg)
Deep Foundations
Pile Foundations
All deep foundation photos courtesy of Geo-Photo album (Ross Boulanger and Mike Duncan)
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Deep Foundations
Pile Foundations
Note excavation outside of forms
![Page 41: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/41.jpg)
Deep Foundations
Pile Foundations
Note excavation outside of forms
![Page 42: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/42.jpg)
Deep Foundations
Drilled Shaft Foundations
![Page 43: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/43.jpg)
Deep Foundations
Drilled Shaft Foundations
![Page 44: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/44.jpg)
Deep Foundations
Drilled Shaft Foundations
![Page 45: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/45.jpg)
Deep Foundations
Drilled Shaft Foundations
![Page 46: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/46.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 47: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/47.jpg)
Deep Foundations
Single pile/shaft behavior – vertical loading
Skin resistance
Tip resistance
Applied load
High in clays (adhesion)
Low in sands (friction)
Low in clays (cohesive)
High in sands (frictional)
![Page 48: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/48.jpg)
Deep Foundations
Single pile/shaft behavior – vertical loading
Skin resistance
Applied load
High in clays
Low in sands
Tip resistance
Zero* in clays
Zero in sands
Possible momentary suction
![Page 49: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/49.jpg)
Deep Foundations
Single pile/shaft behavior – vertical loading
Skin resistance
Tip resistance
Applied load
How do we measure vertical load resistance?
![Page 50: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/50.jpg)
Deep Foundations
Pile load test
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Deep Foundations
Single pile/shaft behavior – vertical loading
Skin resistance
Tip resistance
Applied load, Q
Strain gauges
Q
Tip Skin
Qult
![Page 52: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/52.jpg)
Deep Foundations
Single pile/shaft behavior – vertical loading
Skin resistance
Tip resistance
Applied load, Q
Strain gauges
Q
Tip Skin
Qult
Q
d
Qult
Pile head load displacement
Nonlinear soil response means pile
stiffness is not constant
Nonlinear soil response means pile
stiffness is not constant
![Page 53: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/53.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
Applied load
Horizontal plane
No lateral load
Lateral load
![Page 54: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/54.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
Applied load
Horizontal plane
No lateral load
Lateral load
y
p
![Page 55: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/55.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
Applied load
Horizontal plane
Lateral load
y
p
p
y
Stiffness
Strengthpult
![Page 56: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/56.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
Lateral load
y
p
p
y
Pile moves through soil
Soil appears to flow around pile
Soil movement in horizontal plane
Solutions for pult available
pult
At large depths,
![Page 57: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/57.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
Lateral load
y
p
p
y
pult
At shallow depths,
Wedge of soil is pushed up and out
Vertical and horizontal components of movement
![Page 58: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/58.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
At shallow depths,
Wedge of soil is pushed up and out
Vertical and horizontal components of movement
Same resistance in both directions
![Page 59: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/59.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
At shallow depths,
Wedge of soil is pushed up and out
Vertical and horizontal components of movement
Symmetric loading leads to generally
symmetric response
![Page 60: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/60.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
At shallow depths,
Wedge of soil is pushed up and out
Vertical and horizontal components of movement
Much greater resistance to loading in
upslope than downslope direction
![Page 61: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/61.jpg)
Deep Foundations
Single pile/shaft behavior – lateral loading
At shallow depths,
Wedge of soil is pushed up and out
Vertical and horizontal components of movement
Symmetric loading leads to asymmetric
response
![Page 62: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/62.jpg)
Deep Foundations
Determination of p-y behavior – lateral load test
Applied load
Strain gauge pairs
![Page 63: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/63.jpg)
Deep Foundations
Determination of p-y behavior – lateral load test
p
y
shear force
lateral soil resistance
2
2
)(dz
ydEIzM
2
2 )(
dz
zMdp
bending moment
![Page 64: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/64.jpg)
Deep Foundations
Determination of p-y behavior
bending moment
shear force
lateral soil resistance
2
2
)(dz
ydEIzM
2
2 )(
dz
zMdp
![Page 65: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/65.jpg)
Deep Foundations
Determination of p-y behavior
p
y
bending moment
shear force
lateral soil resistance
2
2
)(dz
ydEIzM
2
2 )(
dz
zMdp
Nonlinear soil response means lateral stiffness is
not constant
Nonlinear soil response means lateral stiffness is
not constant
![Page 66: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/66.jpg)
Deep Foundations
sand
stiff clay
static cyclic
soft clay
Rate-dependence has been observed in some fine-grained soils (increases with increasing plasticity)
May provide ~ 10% increase in stiffness/strength for 10-fold increase in strain rate
Implies frequency-dependence in dynamic stiffness
![Page 67: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/67.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 68: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/68.jpg)
Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
EIy
zQ
y
zm
y
tp
4
4
2
2
2
2
P y
yt
y
ty
y
tG rff
ffu, , , , , , ,
2
2
Dynamic beam on nonlinear Winkler foundation
![Page 69: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/69.jpg)
Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
Dynamic beam on nonlinear Winkler foundationNF FF
NF FF
NF FF
NF FF
NF FF
NF FF
NF FF
NF FF
Free-fielddisplacement
![Page 70: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/70.jpg)
Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
p
y
D
y.
m (1,1)nf
m (2,1)nf
m (1,2)nf
m (2,2)nf
Near-field element
Nonlinear, inelastic behavior close to pile
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Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
Far-field element
Frequency-dependent radiation damping
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Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
Far-field element
Frequency-dependent radiation damping
yffk k k
c c c
1 2 3
1 2 3
mff
![Page 73: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/73.jpg)
Deep Foundations
Analysis of deep foundation response – lateral loading, single foundation
Far-field element
Frequency-dependent radiation damping
yffk k k
c c c
1 2 3
1 2 3
mff
c c2 3
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.50
1
2
3
4
5
6
7
8
Dimensionless Frequency
Stif
fnes
s
Real part
Imaginary part
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Deep Foundations
Analysis of deep foundation response – vertical loading, single foundation
Discretize pile, represent nonlinear skin resistance using t-z curves
Q-z
t-z
What about tip resistance?
t
z
Q
z
Skin resistance generally mobilized quickly
Tip resistance mobilized at larger displacements
![Page 75: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/75.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 76: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/76.jpg)
Deep Foundations
All forms of loading
Q-z
t-zp-y
![Page 77: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/77.jpg)
Deep Foundations
Vertical loading
![Page 78: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/78.jpg)
Deep Foundations
Vertical loading
![Page 79: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/79.jpg)
Deep Foundations
Vertical loading
Adhesion/frictional resistance of soil and interface strength mobilized along length of pile
Adhesion/frictional resistance of soil and interface strength mobilized along length of pile
Tip resistance mobilized in bulb beneath base of foundation
Tip resistance mobilized in bulb beneath base of foundation
Vertical stiffness influenced by entire
soil profile
Vertical stiffness influenced by entire
soil profile
![Page 80: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/80.jpg)
Deep Foundations
Lateral loading at pile head
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Deep Foundations
Lateral loading at pile head
Resistance (stiffness) dominated by near-surface soils
Deeper soils don’t contribute much to lateral resistance (stiffness)
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KHH ≅ Es d ( Ep / Es*
)0.21
Homogeneous soil modulus:
KMHKHH
1
KMM
KHM
1
z
Es
d Es*
KMM ≅ 0.15 Es d 3 ( Ep / Es
* )
0.75
KMH = KHM ≅ - 0.22 Es d 2
( Ep / Es*
)0.50
Single Pile Stiffness – Static Loading
Rocking and swaying are coupled
![Page 83: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/83.jpg)
KHH ≅ 0.6 Es d ( Ep / Es*
)0.35
“Gibson soil” modulus:
KMHKHH
1
KMM
KHM
1
z
Es
d Es*
KMM ≅ 0.15 Es d 3 ( Ep / Es
* )
0.80
KMH = KHM ≅ - 0.17 Es d 2
( Ep / Es*
)0.60
Single Pile Stiffness – Static Loading
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KHH ≅ 0.8 Es d ( Ep / Es*
)0.28
Parabolic soil modulus:
KMHKHH
1
KMM
KHM
1
z
Es
d Es*
KMM ≅ 0.15 Es d 3 ( Ep / Es
* )
0.77
KMH = KHM ≅ - 0.24 Es d 2
( Ep / Es*
)0.53
Single Pile Stiffness – Static Loading
![Page 85: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/85.jpg)
Layered nonlinear soil:
KMHKHH
1
KMM
KHM
1
z
Es
d
Single Pile Stiffness – Static Loading
Use p-y analysis
![Page 86: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/86.jpg)
Deep Foundations
Lateral loading from ground shaking – uniform soil profile
Very flexible pile
High curvatures, low bending moments
High curvatures, low bending moments
Flexural demands can be as high at depth as near the surface
Flexural demands can be as high at depth as near the surface
Pile head motion is same as free-field ground surface motion
Pile head motion is same as free-field ground surface motion
![Page 87: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/87.jpg)
Deep Foundations
Lateral loading from ground shaking – uniform soil profile
Stiff pile
Low curvatures, high bending moments
Low curvatures, high bending moments
Flexural demands can be as high at depth as near the surface
Flexural demands can be as high at depth as near the surface
Pile head motion is different than free-field ground surface motion – reflects distribution of motions along length of pile
Pile head motion is different than free-field ground surface motion – reflects distribution of motions along length of pile
![Page 88: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/88.jpg)
Deep Foundations
Lateral loading from ground shaking – uniform soil profile
High free-field curvature at boundary
High free-field curvature at boundary
Flexural demands can be much higher at depth than near surface
Flexural demands can be much higher at depth than near surface
Soft
Stiff
![Page 89: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/89.jpg)
Deep Foundations
Lateral loading from ground shaking – uniform soil profile
Soft
Stiff
Stiff
High free-field curvature at both boundaries
High free-field curvature at both boundaries
Flexural demands can be high at both locations
Flexural demands can be high at both locations
![Page 90: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/90.jpg)
Deep Foundations - Lateral loading summary
Inertial
Loading from superstructure
Kinematic
Loading from cyclic soil
deformation
Crust
Lateral spreading
Loading from permanent soil
deformation
![Page 91: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/91.jpg)
Deep Foundations
All forms of loading
Q-z
t-zp-y
![Page 92: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/92.jpg)
Deep Foundations
Lateral loading
P
P
d
p
y
Liquefiable soils
p-y curves are “softened” as pore pressures increase – shape remains the same
Actual p-y behavior of liquefied soil is more complicated – stiffness and shape both change
![Page 93: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/93.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
![Page 94: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/94.jpg)
Deep Foundations
Pile Groups
![Page 95: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/95.jpg)
Deep Foundations
Pile Groups
Increased axial load – potential for bearing failure
Decreased axial load – potential for pullout
Lateral loading of pile groups mobilizes axial resistance (t-z, Q-z springs) as well as lateral resistance (p-y springs)
Lateral loading of pile groups mobilizes axial resistance (t-z, Q-z springs) as well as lateral resistance (p-y springs)
![Page 96: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/96.jpg)
Deep Foundations
Pile Groups
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
![Page 97: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/97.jpg)
Deep Foundations
Pile Groups
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
![Page 98: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/98.jpg)
Deep Foundations
Pile Groups
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
![Page 99: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/99.jpg)
Deep Foundations
Pile Groups
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
Axial resistance of piles generally sufficient to greatly reduce pile cap rotation
![Page 100: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/100.jpg)
Deep Foundations
Pile Groups
3 x 3 group
![Page 101: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/101.jpg)
Deep Foundations
Pile Groups
4 x 4 group
![Page 102: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/102.jpg)
Deep Foundations
Pile Groups
Zones of influence
Zones of influence overlap with each other and with other piles
Not all piles produce same resistance
Pile-soil-pile interaction can affect group capacity and stiffness
Piles interact at spacings less than 7-8 diameters
![Page 103: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/103.jpg)
Deep Foundations
Pile Groups
Row
4
Row
3
Row
2
Row
1
Leading row
Trailing rows
Single pile
Row 2
Row 1
Rows 3-5 Leading row takes greatest load
Leading row takes greatest load
Trailing rows take less load
Trailing rows take less load
Group effects handled by p-multipliers
Group effects handled by p-multipliers
Multiple cycles can diminish row effects
Multiple cycles can diminish row effects
![Page 104: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/104.jpg)
Deep Foundations
Pile Groups
Leading row takes greatest load
Leading row takes greatest load
Trailing rows take less load
Trailing rows take less load
Group effects handled by p-multipliers
Group effects handled by p-multipliers
Mokwa, 1999 Multiple cycles can diminish row effects
Multiple cycles can diminish row effects
![Page 105: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/105.jpg)
Deep Foundations
Pile Groups
Single pile has greater bending moment
Single pile has greater bending moment
Leading row piles have largest M in group
Leading row piles have largest M in group
Trailing row moments stabilize after Row 3
Trailing row moments stabilize after Row 3
Rollins et al., 2005
![Page 106: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/106.jpg)
Deep Foundations
Pile Groups – Embedded pile cap
Passive resistance on pile cap
Pile cap can provide substantial contribution to lateral resistance (stiffness)
Pile cap can provide substantial contribution to lateral resistance (stiffness)
Effectiveness can be affected by compaction of backfill soils
Effectiveness can be affected by compaction of backfill soils
![Page 107: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/107.jpg)
Deep Foundations
Pile Groups – High overturning moment
M
High axial demands placed on outer rows of piles – upward and downward
Can lead to yielding of these piles – plastic deformation of soils
M
q
![Page 108: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/108.jpg)
Deep Foundations
Pile Groups – High overturning moment
M
High axial demands placed on outer rows of piles – upward and downward
Can lead to yielding of these piles – plastic deformation of soils
M
q
Dissipated energy
![Page 109: Steve Kramer University of Washington Seismic Site Response Analysis EERI Technical Seminar Series Impact of Soil-Structure Interaction on Response of](https://reader037.vdocuments.us/reader037/viewer/2022103015/551c23a7550346a84f8b5cba/html5/thumbnails/109.jpg)
Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
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Single Pile Stiffness – Dynamic Loading
Under harmonic loading, pile will respond (deform) harmonically
Both amplitude and phase of response will vary with frequency
Can model resistance (pile impedance) as having two parts
Elastic resistance – K(w)
Viscous resistance – C(w)In phase
90o out of phase
Can model dynamic stiffness using stiffness multiplier
K(w) = k(w)Kstatic
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Deep Foundations – Dynamic Amplification Factors
αo = ωd / VS
Frequency dependence for single piles not that strong
Not uncommon to assume k(w) ~ 1
Frequency dependence for single piles not that strong
Not uncommon to assume k(w) ~ 1
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Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
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Methods of Analysis
Direct Analysis
Model entire soil-pile-structure system
Compute response in single analysis
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Direct Analysis
p-y
t-z
Q-z
Attach p-y curves to all
nodesAttach t-z
curves to all nodes
Attach Q-z curves to pile
tip nodes
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Direct Analysis
p-y
t-z
Q-z
Apply depth-varying free-field motions to free ends of p-y, t-z, and Q-z elements
Compute resulting response
Coupled analysis of soil-pile-structure system
Coupled analysis of soil-pile-structure system
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Substructure Modeling
Cut piles at mudline and replace with springs/dashpots
Apply kinematic pile motions at mudline to free ends of horizontal, vertical, and rotational springs
Compute resulting response
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Substructure Modeling
Cut column at pile cap and replace with springs/dashpots
Apply kinematic pile cap motions to horizontal, vertical, and rotational springs at centroid of pile cap
Compute resulting responseSubstructure modeling can provide exact solution for linear system
Can iterate to approximate nonlinear effects using equivalent linearization
No direct way to handle nonlinear systems
Substructure modeling can provide exact solution for linear system
Can iterate to approximate nonlinear effects using equivalent linearization
No direct way to handle nonlinear systems
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Outline
Soil-structure interaction basics
Kinematic interaction
Inertial interaction
Analysis of soil-structure interaction
Effects of soil-structure interaction
Soil-pile-structure interaction basics
Deep foundations
Single pile/shaft behavior
Analysis of single piles
Forms of loading
Pile groups
Dynamic response
Methods of analysis
Conclusions
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Conclusions
Physical behavior of deep foundations is complicated
For buildings …
… kinematic interaction can affect foundation input motions
… inertial interaction effects are more significant
For bridges, wharves, etc.
… kinematic interaction effects can be very significant
… kinematic effects due to permanent deformations can be critical
… inertial interaction effects can still be important
For inertial interaction, estimation of stiffness becomes important
… single piles – resistance mostly flexural
… pile groups – resistance provided by flexural and axial components
… pile cap stiffness can be significant – backfill characteristics important
Approximations to actual behavior frequently required – requires communication between structural and geotechnical engineers
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Thank you
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References
Gazetas, G. (), Chapter 15 in Foundation Engineering Handbook, Winterkorn and Fang, Van Nostrand Reinhold.
Lam, I.P. and Law, H. (2000). “Soil-structure interaction of bridges for seimsic analysis,” Technical Report MCEER-00-0008, 119 pp.
Mokwa, R.L. (1999). “Investigation of the Resistance of Pile Caps to Lateral Loading,” Ph.D. Dissertation, Virginia Tech.
Rollins, K.M., Lane, J.D., Gerber, T. M. (2005). "Measured and Computed Lateral Response of a Pile Group in Sand," J. Geotechnical and Geoenvironmental Engrg., ASCE Vol. 131, No. 1, p. 103-114.
Stewart, J.P. (2000). “Variations between foundation-level and free-field earthquake ground motions” Earthquake Spectra, 16 (2), 511-532.
Stewart, J.P., Fenves, G.L. and Seed, R.B. (1999). “Seismic soil-structure interaction in buildings. II: Analytical aspects,” J. Geotech. & Geoenv. Engrg., ASCE, 125 (1), 26-37.
Stewart, J.P., Seed, R.B., and Fenves, G.L. (1999). “Seismic soil-structure interaction in buildings. II: Empirical findings,” J. Geotech. & Geoenv. Engrg., ASCE, 125 (1), 38-48.