Soil-Pile Interaction in · PDF file• Nonlinear finite element analysis program ......

Soil-Pile Interaction in

FB-MultiPier

Developed by: Florida Bridge Software Institute

Dr. J. Brian Anderson, P.E.

Session Outline

• Introduce FB-MultiPier Software

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

FB-MultiPier

• Nonlinear finite element analysis program

capable of analyzing multiple bridge pier

structures interconnected by bridge spans.

• The full structure can be subject to a full

array AASHTO load types in a static

analysis or time varying load functions in a

dynamic analysis.

FB-MultiPier

• Each pier structure is composed of pier

columns and cap supported on a pile cap

and piles/shafts with nonlinear soil.

• FB-Multipier couples nonlinear structural

finite element analysis with nonlinear static

soil models for axial, lateral and torsional

soil behavior to provide a robust system of

analysis for coupled bridge pier structures

and foundation systems.

FB-MultiPier

• FB-MultiPier performs the generation of the

finite element model internally given the

geometric definition of the structure and

foundation system as input graphically by

the designer.

Coupled Soil-Structure Interaction

Battered Piles

or Shafts

Ship Impact Ship Impact Scour

Scour

Plumb Piles/Shafts

(Shallow Water) (Deep Water)

Live and Dead Loading

Earthquake

Coupled Soil-Structure Interaction

SoilSoil

Florida Pier

FB-MultiPier

Florida Bride Software Institute

• FB-MultiPier and other software for bridge

analysis and design developed and

supported by BSI

• http://bsi-web.ce.ufl.edu

• Good educational discounts (free)

Session Outline

• Introduce FB-MultiPier Software

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

Session Outline

• Introduce FB-MultiPier Software

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

Soil-Structure Interaction

Vertical Nonlinear Spring

Lateral Nonlinear Spring

Torsional Nonlinear Spring

Nonlinear Tip Spring

Driven Piles - Axial Side Model

z r

d z

s

s

s r

s r + D s

r / D r d r

d

z

t

dr

r

t + D t / D r d r

to

r

roott

t (Randolph &

Wroth)

Driven Piles - Axial Side Model

z DZ

Dr

D

D

rd

zd

r

zGt

Also:

Substitute: Grd

zdt

Rearrange: drG

dzt

Previous r

roott

Substitute: drGr

rdz o 0t

rm r0

Also:

2

f

i 1

t

tGG

Substitute:

m

0

r

r

2

f

i

0

1

dr

Gr

rz o

t

t

t

Driven Piles - Axial Side Model

f

0 0

0m

0m

0

m

i

00 ,lnzt

t

t r

rr

rr

r

r

G

r

T-Z (Along Pile)

0

200

400

600

800

1000

1200

0 0.5 1 1.5

z - Displacement (inches)

Tau

0 (

psf) tf = 1000psf

Gi = 3 ksi

Driven Piles - Axial Tip Model

2

f

i0P

P1Gr4

-1Pz

Where: P = Mobilized Base Load

Pf = Failure Tip Load

ro = effective pile radius

= Poisson ratio of Soil

Gi = Shear Modulus of Soil T-Z (At Tip)

0

50

100

150

200

250

300

0 1 2 3 4 5

z - Displacement (inches)

Tip

Load (

kip

s) Pf = 250 kips

Gi = 10 ksi

= 0.3

r0 = 12 inches

(Kraft, Wroth, etc.)

Driven Piles - Axial Properties

• Ultimate Skin Friction (stress), Tauf , along

side of pile (input in layers).

• Ultimate Tip Resistance (Force), Pf , at pile

tip .

• Compressibility of individual soil layers,

I.e. Shear Modulus, Gi , and Poisson’s ratio,

n .

Driven Piles - Axial Properties

• From Insitu Data:

– Using SPT “N” Values run SPT97, DRIVEN,

UNIPILE, etc. to Obtain: Tauf , and Pf

– Using Electric Cone Data run PL-AID, LPC,

FHWA etc. to Obtain: Tauf , and Pf

– Determine G or E from SPT correlations, i.e.

Mayne, O’Neill, etc.

Florida: SPT 97 Concrete Piles

Skin Friction, tf (TSF)

• Plastic Clay:

– tf= 2N(110-N)/4006

• Sand, Silt Clay Mix:

– tf = 2N(110-N)/4583

• Clean Sand:

– tf = 0.019N

• Soft Limestone

– tf = 0.01N

Ultimate Tip, Pf/Area(tsf)

• Plastic Clay:

– q = 0.7 N

• Sand, Silt Clay Mix:

– q = 1.6 N

• Clean Sand:

– q = 3.2 N

• Soft Limestone

– q = 3.6 N

API Side Friction Model - Sand

• tf = K p’0 tan d

where

• k = dimensionless coefficient of lateral earth pressure (ratio of horizontal to vertical normal effective stress(for unplugged K=0.8 and for plugged K=1.0)

• p’0 = effective overburden pressure in stress units

• δ = friction angle between the soil and pile wall, which is defined as d = f – 5o

API Side Friction Model - Sand

API Side Friction Model - Clay

• tf = a cu

where

• cu = undrained shear strength

• a = a dimensionless factor, which is defined as

– a = 0.5-0.5 ≤ 1.0 for ≤ 1.0

– a = 0.5-0.25 ≤ 1.0 for > 1.0

= cu/p’0

API Side Friction Model - Clay

API Tip Model - Sand

• q = p’0 Nq

where

– p’0 = effective overburden pressure in stress units

– Nq = eπtan(f’)tan2(45 + f’/2)

• Qp = qA

• Where

– Qp is the total end bearing capacity

– A is the cross sectional area

API Tip Model Sand

API Tip Model - Clay

• q = 9cu

where

• cu = undrained shear strength

• Qp = qA

where

– Qp is the total end bearing capacity

– A is the cross sectional area

API Tip Model Clay

Cast Insitu Axial Side and Tip Models

• For soil (sands and clays)

– Follow FHWA Drilled Shaft Manual For Sands

and Clays to Obtain Tauf and Pf ( and cu)

– Shape of T-Z cuve is given by FHWA’s Trend

Lines.

• User has Option of inputting custom T-z /

Q-z curves

Cast Insitu - Sand (FHWA):

Qs = p D L sv’

D L

L/2

sv’ = L/2

1.5 .135 L/2) 0.5 1.2> >0.25

Qt = 0.6 NSPT p D 2 / 4 NSPT < 75

Cast Insitu - Clay (FHWA):

D L

Qs = 0.55 Cu p D (L-5’-D)

Qt = 6 [1+0.2(L/D) ] Cu (p D 2 / 4)

Cast Insitu trend line for Sand

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 2 4 6 8 10

Settlement / Diameter (%)

Mo

bil

ize

d S

tre

ss

/ U

ltim

ate

Str

es

s

End Bearing

Side Friction

Cast Insitu trend line for Clay

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 2 4 6 8 10

Settlement / Diameter (%)

Mo

biliz

ed

Str

es

s /

Ult

imate

Str

es

s

End Bearing

Side Friction

Session Outline

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

Torsional Model (Pile/Shaft)

• Hyperbolic Model

– G and Tauf

• Custom T-

Torsional Model (Pile/Shaft)

(rad)

T (F-L)

Tult =1/b

(dT/d)=1/a Gi

Tult = 2p r2 D L tult T = / a + b

Tult = tf Asurf r

tult = Ultimate Axial

Skin Friction

(stress)

Session Outline

• Introduce FB-MultiPier Software

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

Lateral Soil-Structure Interaction

Passive State

Active State

Y

Near Field: Lateral (Piles/Shafts)

r

y

X

P r dF

Lr

s

p

0

2

P r dF

Lr

s

p

0

2

r

Y=5”

sr

sr

Y=0

P = 0 P

Y

Pu

P rStiff

Clay

Sand &

Soft Clay

PPPP

P-y Curves - Reese’s Sand

k

m

b/60 3b/80

x = 0

x = x1

x = x2

x = x3

x = x4

u

p k

y k

y m

yu p m

p u

m

y

P

ks x

Pu is a function of

f, , and b

Y is a function

of b (pile diameter)

0.0

0.5

1.0

PPU

y

y50

1.0 8.0

p

p0.5

y

yu 50

1 / 3

Matlock’s Soft Clay

Pu is a function of

Cu, , and b

Y is a function of

y50 (50)

Reese’s Stiff Clay Below Water

Deflection, y (in.)

Soil

Res

ista

nce

, p

(lb

/in

.)

18Asy506Asy50y50Asy50

Esi = ksx

0.5Pc

0

P Pcy

y 0 5

50

0 5. ( )

.

P poffset cy A y

A ys

s

0 055 50

50

1 25. ( )

.

STATIC

Essp

yc

0 0625

50

.

Pc is a function of

C, , ks and b

Y is a function of

y50 (50)

O’Neill’s Integrated Clay

Pu is a function of

c, and b

Fs is a function of 100

Yc is a function of b and 50

Soil Properties for Standard Curves

• Sand:

– Angle of internal friction, f

– Total unit weight,

– Modulus of Subgrade Reaction, k

• Clay or Rock:

– Undrained Strength, Cu

– Total Unit Weight,

– Strain at 50% of Failure Stress, 50

– Optional: k, and 100

Soil Information

Help Menu EPRI (Kulhawy & Mayne)

P-y Curves from Insitu Tests

• Cone Pressuremeter

• Marchetti Dilatometer

Insitu PMT & DMT Testing

Cone Pressuremeter

Cone Pressuremeter

(Robertson, Briaud, etc.)

Marchetti Dilatometer

Pressuremeter P-y Curves Auburn, Alabama

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5 10 15 20 25 30 35 40

y (mm)

P (

kN

/mm

)

1 m

2 m

3 m

4 m

6 m

8 m

10 m

PMT P-y Curves - Auburn

Dilatometer P-y Curves Auburn, Alabama

0

500

1000

1500

2000

2500

0 50 100 150 200 250 300 350

y (mm)

P(k

N/m

)

0.6 m

2.1 m

3 m

4.2 m

6.3 m

7.2 m

DMT P-y Curves - Auburn

Actual and Predicted Lateral Top of Shaft Deflections

Auburn, Alabama

0

100

200

300

400

500

600

700

800

900

1000

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Lateral Deflection (mm)

La

tera

l L

oa

d (

kN

)

PMT

DMT

CPT

Shaft 1

Shaft 2

Shaft 3

Shaft 6

Auburn Predictions

P-y Curves for PMT1

Pascagoula, Mississippi

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140 160 180 200

y (mm)

P (

kN

/mm

)

9.7

10.7

11.7

12.7

13.8

14.8

15.8

16.8

17.8

18.8

PMT P-y Curves Pascagoula

P-Y Curves from DMT 1

Pascagoula, Mississippi

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0 10 20 30 40 50 60

p (mm)

y (

kN

/mm

)

9.6

10.8

11.7

12.6

16.0

16.9

17.8

DMT P-y Curves Pascagoula

Pascagoula Predictions

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 10 20 30 40 50

Deflection (mm)

Lo

ad

(kN

) DMT

PMT

Actual

Instrumentation & Measurements

• Strain gages

– Measure strain

– Calculate bending moment, M = ε(EI/c), if EI of section known

– “high tech”

• Slope inclinometer

– Measures slope

– Relatively “low tech”

Theoretical Pile Behavior

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

Strain Gages Bending Moment

Bending Moment versus Depth

0

1

2

3

4

5

6

0 200 400 600 800 1000 1200

Bending Moment (kN*m)

Dep

th (

m) 36

62

93

121

153

182

211

258

Lateral

Load in

Kilonewtons

Bending Moment vs. Depth

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

Two Integrals to Deflection

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

Two Derivatives to Load

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

z

z

Non-linear Concrete Model

Test Pile T1

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

0.0E+00 2.0E-03 4.0E-03 6.0E-03 8.0E-03 1.0E-02

Curvature, f (1/m)

EI (k

N-m

2)

P-y Curves from Strain Gages

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35

Displacement, y (mm)

p (

kN

/m)

1.0

2.0

3.0

4.1

D. to G.S.

(m)

Slope Inclinometer Slope

Deflection versus Depth

-2

0

2

4

6

8

10

-0.01 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07

Horizontal Displacement (m)

De

pth

(m

)

36

62

90

122

153

183

208

243

Lateral

Load in

Kilonewtons

Slope Inclinometer → Slope vs. Depth

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

One Integral to Deflection

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

Three Derivatives to Load

PM

Pile

Y(z)

Deflection

Y’(z)

Slope

M(z)

Moment

M’(z)

Shear

P(z)

Soil Reaction

z

z

z

P-y Curves from Slope Inclinometer

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35

Displacement, y (mm)

p (

kN

/m)

1.0

2.0

3.0

4.0

D. to GS

(m)

0

20

40

60

80

0 5 10 15 20 25 30 35

Displacement, y (mm)

p (

kN

/m)

SG

inc

PMT/DMT

SPT

Comparison of P-y Curves

Prediction of Pile Top Deflection

0

50

100

150

200

250

300

0 20 40 60 80 100

Top Displacement (mm)

Lo

ad

(k

N)

W. line

FLPIER-sg

FLPIER-inc

P-y Curves Available in FB-Pier

• Standard

– Sand

• O’Neill

• Reese, Cox, & Koop

– Clay

• O’Neill

• Matlock Soft Clay Below Water Table

• Reese Stiff Clay Below Water Table

• Reese & Welch Stiff Clay Above Water Table

P-y Curves Available in FB-Pier

• User Defined

– Pressuremeter

– Dilatometer

– Instrumentation

• Strain Gages

• Slope Inclinometer

Session Outline

• Introduce FB-MultiPier Software

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile

Pile Element Model

hh2

h2

X

Z

X

Y

(Top View)

(Side View)

M M

M M

1 3

2 4

Universal Joint

Rigid center-blocks

Rigid end Block

Spring

Curvature-Strain-Stress-Moment

a) Strain due to

z-axis bending

b) Strain due to

y-axis bending

c) Strain due to

axial thrust

N

N

F

,

F

,i

i

1

2

x

y

z

dF

dA

i

i

e) Stress-strain relationship

d) Combined strains

Stress-Strain Curves for Concrete & Steel

Strains -> Stress -> Moments

x

y

z

dF

dA

i

i

d) Combined strains

dFi=si*dAi

n_PointsIntegratio

x ydF*M

Stiffness of Cross-Section: Flexure, Axial

M

x

y

z

dF

dA

i

i

d) Combined strains

n_PointsIntegratio

x ydF*M

Failure Ratio Calculation

My

Mx

P

Mxo

Myo

Pactual

Failure Ratio = Surface Length

Actual Length

Pile Material Properties

References:

• Robertson, P. K., Campanella, R. G., Brown, P. T., Grof, I., and Hughes, J. M., "Design of Axially and Laterally Loaded Piles Using In Situ Tests: A Case History,“ Canadian Geotechnical Journal, Vol. 22, No. 4, pp.518-527, 1985.

• Robertson, P. K., Davies, M. P., and Campanella, R. G., "Design of Laterally Loaded Driven Piles Using the Flat Dilatometer," Geotechnical Testing Journal, GTJODJ, Vol. 12, No. 1, pp. 30-38, March 1989.

• Reese, L. C., Cox, W. R. and Koop, F. D (1974). "Analysis of Laterally Loaded Piles in Sand," Paper No. OTC 2080, Proceedings, Fifth Annual Offshore Technology Conference, Houston, Texas, (GESA Report No. D-75-9).

• Hoit, M.I, McVay, M., Hays, C., Andrade, P. (1996). “Nonlinear Pile Foundation Analysis Using Florida Pier." Journal of Bridge Engineering. ASCE. Vol. 1, No. 4, pp.135-142.

• Randolph, M. and Wroth, C., 1978, “Analysis of Deformation of Vertically Loaded Piles, ASCE Journal of Geotechnical Engineering, Vol. 104, No. 12, pp. 1465-1488.

• Matlock, H., and Reese, L., 1960, “Generalized Solutions for Laterally Loaded Piles,” ASCE, Journal of Soil Mechanics and Foundations Division, Vol. 86, No. SM5, pp. 63-91.

Session Outline

• Identify and Discuss Soil-Pile Interaction Models

– Precast & Cast Insitu Axial T-Z & Q-Z Models

– Torsional T- Models

– Lateral P-Y Models

– Nonlinear Pile Structural Models

• FB-MultiPier Input and Output

– Example #1 Single Pile