Prepared byJ. P. Singh & Associates

in association with

Mohamed Ashour, Ph.D., PE West Virginia University Tech

andGary Norris Ph.D., PE

University of Nevada, Reno

APRIL 3/4, 2006

Computer Program DFSAPDeep Foundation System Analysis Program

Based on Strain Wedge Method

Washington StateDepartment of Transportation

PHASE I • S-SHAFT PROGRAM FOR SHORT SHAFTS• ONE-ROW SHAFT GROUP (AVE. SHAFT)• SHAFT CAP (for one row of shafts)• SOIL LIQUEFACTION

WORK PROGRESS

PHASE II• INTERMEDIATE / LONG PILE/SHAFT• SHAFT/PILE GROUP• ISOLATED SHAFT AND SHAFT GROUP

IN LIQUEFIABLE SOIL• LATERAL SOIL SPREAD• PILES/SHAFTS IN SLOPING GROUND• ROTATION & DISPLACEMENT

FOUNDATION STIFFNESSES (K11, K22,.......)

Linear and Nonlinear Equivalent Stiffness Matrix for Bridge Foundations

PRESENTATION PROGRAM

Comparison between Current Practice and the Strain Wedge Model Technique Used in Program DFSAP

Soil Liquefaction and Anticipated Lateral Spread, and their Effect on Pile/Shaft Response

Short/Intermediate/Long Pile/Shaft in Liquefied & Nonliquefied Soil Profiles, and Pile Cap Effect

DFSAP Program Demonstration (Input and Output Data)

Axially Loaded Piles and Piles in Sloping Ground

Y

X X

Z

Z

Y

Foundation Springs in the Longitudinal Direction

K11

K22K66

Column Nodes

Longitudinal

Transvers

e

y

p(Es)1

(Es)3

(Es)4

(Es)2p

p

p

y

y

y

(Es)5

p

y

Mo

Po

Pv

Laterally Loaded Pile as a Beam on Elastic Foundation (BEF)

Traditional p-y Curve Does Not Account for the Following:

• Pile Bending Stiffness (EI)• Pile Head Conditions (Free/Fixed)• Pile Cross-Section Shape (Square/Circular/H-Shape)• Pile-Head Embedment Below Ground• Soil Profile Continuity (Winkler Springs)• It was developed for Long Piles• Empirical Parameters

• Soil Liquefaction and Lateral Soil Spread

• Pile Group

• Vertical Side Shear Resistances (Large Diameter Shaft)

DIFFERENCES BETWEEN THE TRADITIONAL P-Y CURVE AND PROGRAM DFSAP

y

p(Es)1

P o

(Es)3

(Es)4

(Es)2p

p

p

y

y

y

(Es)5

p

y

Laterally Loaded Pile as a Beam on Elastic Foundation (BEF)

P P

K1 K2

4 ft4 ft

Effect of Structure Cross-Sectional Shape on Soil Reaction

Effect of the Footing Flexural Rigidity (EI) on the Distribution of the Soil Reaction

q per unit area

B

CL

q

0.5q

Kr =

Kr = 0

Rigid Footing, Kr =

Flexible Footing, Kr = 0

Footing

H

(1-2s) EP H3

6 (1-2P) Es B3

Kr =

As presented by Terzaghi (1955) and Vesic (1961)

The traditional p-y curve (in LPILE) does not account for the pile/shaft EI variationB

ased

on

th

e S

trai

n

Wed

ge M

odel

An

alys

isS tif f P ile F lex ib le P ile

p -y C u rv e a t a D ep th o f 1 .2 2 m

D en se S an d

L o o se S an d

E f f ec t o f P ile B en d in g S tif f n e ss o n th e p -y C u rv e in S an d

0 4 0 8 0 1 2 0

P ile D e f le c tio n , y , m m

0

1 0 0

2 0 0

3 0 0

4 0 0

Soi

l-P

ile

Rea

ctio

n, p

, kN

/ m EI

0.1 EI

F ree -H ea d P ileF ix ed -H ea d P ile

E ffect o f P ile -H ea d C o n d itio n s o n th e p -y C u rv e in S a n d

p -y C u rv es a t 1 .2 2 -m D ep th

D en se S a n d

L o o se S a n d

0 40 80 120P ile D eflec tio n , y , m m

0

200

400

600

Soi

l-P

ile R

eact

ion,

p, k

N /

m

Kim et al. (ASCE J., 2004)

LARGE DIAMETER SHAFT

z

T

y

p

Soil-Shaft Horizontal Resistance

Soil-Shaft Shear Resistance

Neglected with Long Shafts

PoMo

PvPoo

Moo

Pvy

FP

v

Mt

Fv

FP

FP

Fv

Fv

Vt

Ft

The Basic Strain Wedge Model in Uniform Soil

SAND

CLAY

C-

ROCK

Fig. 5 Relationship between the real Mobilized stress zones and the SW model passive wedges

Mobilized zones asassessed experimentally

m

Pile

Pile head load Po

Successive mobilizedwedges

m

(c) Forces at the face of the soil passive wedge (Section elevation A-A)

m

m

m

Pile

Real stressed zone

F1

F1

No shear stress because these are principle stresses

ds

dx

h

h * CD* dx = * CD * ds sin m

A

VO

Side shear () that influences the oval shape of the stressed zone

(b) Force equilibrium in a slice of the wedge at depth x

m

KVO

p

Yo

h

x

Hii

i-1

Sublayer i+1

Sublayer 1

Plane taken to simplify analysis (i.e. F1’s cancel)

C

B

A

h

y

p(Es)1

P o

(Es)3

(Es)4

(Es)2p

p

p

y

y

y

(Es)5

p

y

Stre

ss

Strain

fs

s

y

Yield Stress (f )y

soE

Uniaxial Elastic-Perfectly PlasticNumerical Steel Model

E sE s E s

Stress-Strain Model for ConfinedConcrete in Compression

fccEc

Ecc

cc

cuCompressive Strain, c

Com

pres

sive

str

ess,

fc

Pile/Shaft Nonlinear Material Modeling

Validation Example (Chapter 6)

Shaft W idth

Reinforced C oncrete D rilled Shaft

x x

Longitudinal S tee l

Shaft Section# 1Segm ent length = 40 ftShaft d iam eter = 6 .0 ftfc o f concrete = 6100 psify o f the stee l bars = 71 KsiR atio of S teel bars (A s/A c)= 2%R atio of Transversesteel (A 's/A c)= 0.5%

Shaft Section# 2Segm ent length = 48 ftShaft d iam eter = 6.5 ftfc o f concrete = 6100 psify o f the stee l bars = 71 KsiR atio of S teel bars (A s/A c)= 1.8%R atio of T ransversesteel (A 's/A c)= 0.5%

UCLA TEST

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

0.0000 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.0008

Curvature (1/in)

Mo

me

nt

(kip

-ft)

Experimental

X_Section

swm

0

50000

100000

150000

200000

250000

300000

350000

0 5 10 15 20

Lateral Deflection, inches

Lo

ad, l

bs

Experiment SWM

Shaft Head Response at the UCLA Test

0 4 8 12 16Top d isp lacement (in )

0

10

20

30

La

tera

l L

oa

d (

kip

s)

0 100 200 300 400

Top d isp lacement (mm)

0

50

100

150

La

tera

l L

oa

d (

kN

)

FEMp-y (E xp.)p-y (A P I)SW MM easured

2-ft-Diameter Free-Head Shaft Response at the UCLA Test

Shaft Length = 25 ft (Bridge Conference, Oct. 2005)

Pile H ead Shaft

P o

2-ft Diameter Shaft

CLA

YS

and

C lay

G round Surface

20 ft

5 ft

Su = 3900 psf

e50 = 0 .007

f = 38 o

e50 = 0 .003

PILE GROUP

PILE GROUPPo

Pv

P-multiplier (fm) concept for pile group (Brown et al. 1988)

y

p

pgroup = fm psingle

psingle

Pile in a group

Single pile

PILE GROUP

Configuration of the Mobilized Passive Wedges, and Associated Pile Group Interference

D ev e lo p in g P ass iv e S o il W ed g e s

P ile in Q u e stio n

F ig . 7 H o rizo n ta l ( la te ra l an d fro n ta l) in te rac tio n fo r a p rticu la r p ile in a p ile g ro u p a t a g iv en d e p th

P ile T y p e 1

P ile T y p e 2 L o a d in g D irectio n

L ea d in g R o w

T ra ilin g R o w

S P 1S P 1

P ile T yp e 3

P ile T yp e 4

B y P o sitio n

S P 2

S P 2

T ra ilin g R o w

Horizontal passive wedge interference in pile group response

Pile Pile

Overlap of stresses based on elastic theory (and nonuniform shaped deflection at pile face)

Overlap employed in SW model based on uniform stress and pile face deflection

(Po)g (Po)gUniform pile face movement

Validation Examples (Report, Chapter 6)

• Lateral response of pile-group (P vs. Yo)• Response of individual piles in a group• p-y curves of individual piles

0 25 50 75P ile D eflection, y, m m

0

40

80

120

160

200

Soi

l-Pile

Rea

ctio

n, p

, kN

/m

0 25 50 75P ile D eflection, y, m m

0

0.2

0.4

0.6

0.8

1

P-M

ultip

lier

= (

p Sin

gle

/pP

ile in

a g

rou

p)

P ile Type 4 (Inside P ile)

P ile Type 3 (O utside P ile )

Ind iv idual P ile in the Leading R owAverage Leading R ow

Pile Type 3

P ile Type 4

S ingle P ile

P-m ultip lier a t 0.9 m below p ile head

p-y curve at 0 .9 m be low p ile head

S ing le Pile

G ro u p

0 20 40 60D e fle c tio n a t L o a d P o in t, Y o, m m .

0

25

50

75

100

Ave

rage

Loa

d pe

r P

ile, P

o, k

N

C om p ress ion S trok e

T en sio n S tro k e

S W M o d e lM easu red(C o m p ress io n S tro k e )(T en sio n S tro k e )

Fig. 15. Latera l p ile -head la teral load vs. deflection for an iso lated p ile and an average p ile in a 3 x 3 group in sand (a fter M orrison and R eese, 1986)

D e v e lo p in g P a ss iv e S o il W e d g e s

P ile in Q u e stio n

F ig . 7 H o rizo n ta l ( la te ra l an d fro n ta l) in te rac tio n fo r a p rticu la r p ile in a p ile g ro u p a t a g iv en d ep th

P ile T y p e 1

P ile T y p e 2

L oad in g D irection

L ea d in g R ow

T ra ilin g R ow

T ra ilin g R ow

S P 1S P 1

P ile T y p e 3

P ile T y p e 4

B y P o sitio n

S P 2

S P 2

Morrison and Reese Pile Group Test in Sands (1986)

S W M o d e lM e asu re d

0 2 0 4 0 6 0 8 0D e fle c tio n a t L o a d P o in t, Y o, m m .

0

40

80

120

160

200

Ave

rage

Loa

d pe

r P

ile,

Po

, kN

L ay e red C lay S o il (R o llin s e t a l. 1 9 9 8 )

Validation Example (Report, Chapter 6)

• Limitations of traditional p-y curves• Lateral response of isolated shaft

and shaft-group• Vertical shear side resistance effect on

diameter shafts

-0 .5 m0.0 m

3.0 m

8.0 m

12.0 m

17.0 m

25.0 m

32.0 m

= 35 o

= 19 kN /m 3

= 35 o

= 9.2 kN /m 3

= 34o

= 9.4 kN /m 3

= 34o

= 9.2 kN /m 3

S u=121.3 kN /m 2

= 9.2 kN /m 3

50 = 0.005

S u=115 kN /m 2

= 9.2 kN /m 3

50= 0.005

S u=60 kN /m 2

= 9.2 kN /m 3

50= 0.007

Sand

S and

Sand

Sand

C lay

C lay

C lay

Free head shaft

a) O rig inal so il p ro file

4.5 m

Loading D irection

b) S ix 1 .5-m -D iam eter Shaft G roup (F ixed H ead)

Shaft B1

Shaft B2

The Taiwan Test by Brown et al. 2001

In order to match the measured data using LPILE, the traditional p-y curves were modified as shown above (Brown et al. 2001)

0 40 80 120 160 200Pile Head Deflection, Yo, mm

0

1000

2000

3000

4000

Pile

He

ad

Lo

ad

, Po,

kN

Measured (Brown et al. 2001)Predicted (SW Model)No V. Side ShearWith V. Side Shear

Single 1.5-m-Diameter Shaft (B1)

Free-head

0 10 20 30 40C ap D eflection, Y g, m m

0

4000

8000

12000

Pile

Gro

up

Lat

era

l Loa

d, k

N

Measured (Brown et al. 2001)Predicted (SW Model)

Latera l R esponse of a (3 x2) P ile G roup

Fixed head

Validation Example (Treasure Island Test)

• Validation of pile classification in DFSAP• Response of individual piles in a group

Treasure Island 3 x 3 Pile Group Test (Rollins et al., ASCE J., No. 1, 2005)

(Rollins et al. 2005, ASCE Journal)

Validation Example Report, Chapter 5

• 3 x 3 Pile group in soil Profile-S5 from WSDOT Design Manual

• Pile Cap Contribution• Pile-head effect (free and fixed)

Loading Direction

P ile in Q u e stio n

H o rizo n ta l (la te ra l an d fro n ta l) in te rac tio n fo r a p rticu la r p ile in a p ile g ro u p a t a g iv en d ep th

P ile T y p e 1

P ile T y p e 2

L oad in g D irection

L ea d in g R ow

T ra ilin g R ow

T ra ilin g R ow

S P 1S P 1

P ile T y p e 3

P ile T y p e 4

B y P o sitio n

S P 2

S P 2

3 x 3 SHAFT GROUP OF 2-FT LENGTH IN SOIL PROFILE S-7 FREE-HEAD, EXAMPLE 2

0 2 4 6 8Shaft D eflection, Y o, in

0

100

200

300

400

Sha

ft-H

ead

Load

, Po, k

ips

Pile Type 1Pile Type 2Pile Type 3Pile Type 4

Isolated Shaft

0 2 4 6 8Shaft D eflection, Y o, in

0

100

200

300

400

Sha

ft-H

ead

Loa

d, P

o, k

ips

Isolated Shaft

Average Shaft

0 0.4 0.8 1.2 1.6Shaft D eflection, Y o, in

0

100

200

300

400

500

Sha

ft-H

ead

Load

, Po, k

ips

Pile Type 1Pile Type 2Pile Type 3Pile Type 4

Iso la ted Shaft

0 0.4 0.8 1.2 1.6Shaft D eflection, Y o, in

0

100

200

300

400

500

Sha

ft-H

ead

Loa

d, P

o, k

ips

Isolated Shaft

Average Shaft

3 x 3 SHAFT GROUP OF 2-FT LENGTH IN SOIL PROFILE S-7 FIXED-HEAD, EXAMPLE 2

FIXED-HEADFREE-HEAD

0 2 4 6 8Shaft D eflection, Y o, in

0

400

800

1200

1600

2000

Sha

ft-H

ead

Load

, Po,

kip

s

Cap + Shafts

Cap

Shafts

FR EE H EAD

0 0.4 0.8 1.2 1.6Shaft D eflection, Y o, in

0

400

800

1200

1600

2000

Sha

ft-H

ead

Load

, Po,

kip

s

Cap + Shafts

Cap

Shafts

QUESTIONS ????•