Displacement-based calculation method on soil-pile interaction of PHC...

Displacement-based calculation method

on soil-pile interaction of PHC pipe-piles

Dr. Huang Fuyun

Fuzhou University

31st May, 2017

Seattle, WA

Outline

Background

Testing introduction

Testing results

Simple calculation

Conclusions

1.Background

Pier

Deck slab

Abutment

Pile

Girder

Backfill

Pavement Approach slab

AbutmentBackfill

Girder

Pier

Abutment

Piles

Soil spring

Soil spring

Soil spring

Soil spring MN

F Friction

Approach slab

Pier

Deck slab

Abutment

Piles

Girder

Backfill


AbutmentBackfill

Under temperature and seismic load, displacement of superstructure is

absorbed by piles and piles are under cyclic load. To satisfy demand of

superstructure deformation, flexible piles are used most frequently.

H-steel piles have been widely used under Integral Abutment in North

America and Europe, because of good flexural property and ductility.

1.Background

ETsum

Pier

Deck slab

Abutment

Piles

Girder

Backfill


AbutmentBackfill

Researchers of Iowa State University used PC piles in IJB and did

researches on behavior of these piles and field monitoring on IJB using PC

piles.

2004, researches on behavior of prestressed concrete square piles were

conducted by Prof. Edwin from Tennessee University, which proved that

PC piles can be used in IJB.

1.Background

Pier

Deck slab

Abutment

Piles

Girder

Backfill


AbutmentBackfill

“m” method is linear and elastic with a limit 8-10mm in Chinese Code.

“p-y” method is complex or accurate enough for RC piles?

1.Background

t

PHC model piles C80 concrete (has a compressive strength of 82.1 MPa)

With a diameter of 155mm，length of 2.75m

7-wires prestressed steel strand with a diameter of 11.10mm

Labeled as PHC-1 to PHC-4

2. Testing introduction

NumberDiameter

（mm）

Pile

Length

（m）

Wall

Thickness

（mm）

Prestressed

Degree λ

Stirrup

Spacing

（mm）

Deformation

Coefficient

a

Calculate Pile

Length（m）

PHC-1

155 2.75

52.5 0.0 60 1.697 3.988

PHC-2 52.5 0.25 60 1.697 3.988

PHC-3 52.5 0.50 60 1.697 3.988

PHC-4 40.0 0.57 60 1.715 4.031

Soil Container (rigid box) Circular

Height of 2.5m

Diameter of 1.5m

Wall thickness of 10mm

4 diagonal braces

Soil (medium dense sand) Sand from Min River

Water Content

(%)

Density

(g/cm3)void ratio

Internal friction

angle (°)

Average SPT

blow count

4.6 1.90 0.59 35 11


Sensor arrangement Strain gages

14 strain gages were installed on piles

with an equal spacing of 350mm,

labeled as S1 to S14.

24

50

10

02

50

35

03

50

35

03

50

35

03

50

S1 S8

S2

S3

S4

S5

S6

S7

S9

S10

S11

S12

S13

S14

Soil surface


Sensor arrangement Earth pressure cells

12 earth pressure cells were

installed on piles with an equal

spacing of 350mm, labeled as T1 to

T12.

10

04

25

35

03

50

35

03

50

35

01

75

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

Soil surface


Sensor arrangement Displacement meters

8 displacement meters were installed,

labeled as D1 to D8.

D1

D2

D3

D4

D5

D6

D7

D8

10

02

50

35

03

50

35

03

50

35

03

50

40

0Soil surface


Method of displacement meters placement


Loading（Displacement loading method） Initial stage: 2 mm, 5mm, 8mm and 10mm.

10mm to 30mm: increase by 5mm.

After 30mm: increase by 10 mm, and the test end until the lateral force

decreases to 85% of peak value.

Load speed: 1.0mm/s. 3 cycles every load grade。

Dis

pla

cem

ent

load

(m

m)

..

-10-8

-5

-2

..

108

5

2


3.1 Failure modes

3. Testing Results

PHC-2 PHC-4

3.2 Displacement

-20 0 20 40 60 80 100 120 140 1602.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Em

bed

ded

dep

th (

m)

Displacement (mm)

2mm 5mm 8mm 10mm

15mm 20mm 25mm 30mm

40mm 50mm 60mm 70mm

80mm 90mm 100mm 110mm

0 2 4 6 8 102.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Em

bedded d

epth

(m

)

Displacement (mm)

3. Testing Results

PHC-4

3.3 Hysteretic curve and skeleton curve

-150 -100 -50 0 50 100 150-20

-15

-10

-5

0

5

10

15

20

Displacement mm

Load

kN

-150 -100 -50 0 50 100 150-20

-15

-10

-5

0

5

10

15

20

Load

kN

Displacement mm

-150 -100 -50 0 50 100 150-20

-15

-10

-5

0

5

10

15

20

Load

kN

Displacement mm

-Pu=-12.4kN

-yu=-109.6mm -P

cr=-5.5kN

-ycr=-9.9mm

Pcr=5.4kN

ycr=10.0mm P

u=11.5kN

yu=110.0mm

-150 -100 -50 0 50 100 150-20

-15

-10

-5

0

5

10

15

20

Lo

ad k

N

Displacement mm

-Pu=-16.3kN

-Yu=-119.1mm

-Pcr=-5.1kN

-Ycr=-9.2mm

Pcr=5.3kN

Ycr=9.9mm

Pu=15.9kN

Yu=119.4mm

PHC-2PHC-4

PHC-2PHC-4

3. Testing Results

3.4 Strain distribution and strain history

-400 -300 -200 -100 0 100 200

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Em

bed

de

d d

epth

(m

)

strain ×10-6

2mm

5mm

8mm

10mm

15mm

0 5 10 15 20 25 300

30

60

90

120

150

180

210

theoretic crack strain value

Ten

sile

str

ain

×1

0-6

Displacement load (mm)

0.35m depth

0.70m depth

1.05m depth

1.40m depth

0 10 20 30 40 50 60 70 80 900

-250

-500

-750

-1000


0.35m depth

0.70m depth

1.05m depth

1.40m depth

Co

mp

ress

ive

stra

in ×

10

-6

-400 -300 -200 -100 0 100 200

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Em

bed

de

d d

epth

(m

)

strain ×10-6

2mm

5mm

8mm

10mm

15mm

0 5 10 15 20 25 300

30

60

90

120

150

180

210

240


theoretic crack strain value

0.35m depth

0.70m depth

1.05m depth

1.40m depth

Ten

sile

str

ain

×1

0-6

0 10 20 30 40 50 60 70 80 900

-250

-500

-750

-1000

Co

mp

ress

ive

stra

in ×

10

-6Displacement load (mm)

0.35m depth

0.70m depth

1.05m depth

1.40m depth

PHC-2 PHC-2 PHC-2

PHC-4 PHC-4 PHC-4

3. Testing Results

3. Testing Results

0 10 20 30 40 50 60 70 80

0

20

40

60

80

100

120

Ea

rth

Pre

ssu

re (

kPa

)

Displacement Loads (mm)

T1

T2

T3

T4

T5

T6

-10 0 10 20 30 40 50 602.5

2.0

1.5

1.0

0.5

0.0

-0.5

Earth Surface

Em

bed

de

d D

epth

(m

)

Earth Pressure (kPa)

2mm

5mm

8mm

10mm

15mm

-5 0 5 10 15 20 25-5

0

5

10

15

20

25

30

35

Eart

h P

ress

ure

(k

Pa)

Displacement Loads (mm)

T1

T2

T3

T4

T5

T6

-5 0 5 10 15 20 25 302.5

2.0

1.5

1.0

0.5

0.0

-0.5

Em

bed

ded

Dep

th (

m)


2mm

5mm

8mm

10mm

15mm

3.5 Pile soil pressure

PHC-2

PHC-2

PHC-4

PHC-4

4. Calculation on pile-soil interaction

zCzCdzCP ssu 321 ,)/(min API

)tantan1(

)tan(

tan

cos)tan(

sintan[ a

D

z

aD

zKzAP ssu

])tansin(tantan as KaD

zK

Reese LFP

Broms 3u s pP K Dz

nn

prsu azDKSP )( 0

22 Guo

zyzmP u“m”

4.1 Soil pressure calculate


0 15 30 45 602.5

2.0

1.5

1.0

0.5

0.0

-0.5

Em

bed

ded

Dep

th (

m)


API 1993

Reese

Broms

Guo

Test

0 20 40 60 802.5

2.0

1.5

1.0

0.5

0.0

-0.5

Em

bed

ded

Dep

th (

m)

Soil pressure

API 1993

Reese

Broms

Guo

Test

0 25 50 75 1002.5

2.0

1.5

1.0

0.5

0.0

-0.5

Em

bed

ded

Dep

th (

m)


API 1993

Reese

Broms

Guo

Test

0 25 50 75 100 1252.5

2.0

1.5

1.0

0.5

0.0

-0.5

Em

bed

ded

Dep

th (

m)

Soil pressure

API 1993

Reese

Broms

Guo

Test


0 3 6 9 12 150

15

30

45

60

Ear

th P

ress

ure

(kP

a)

Displacement (mm)

API 1993

Reese

Broms

Guo

'm' method

PHC-1

PHC-2

PHC-3

0 1 2 3 4 5 60

30

60

90

120

150

Ear

th P

ress

ure

(kP

a)

Displacement (mm)

API 1993

Reese

Broms

Guo

'm' method

PHC-1

PHC-2

PHC-3

0.0 0.5 1.0 1.50

40

80

120

160

Ear

th P

ress

ure

(kP

a)

Displacement (mm)

API 1993

Reese

Broms

Guo

'm' method

PHC-1

PHC-2

PHC-3

2 2

0

1 2 3

tan sin tan[ (1 tan tan )

tan( ) cos tan( )

tan (tan sin 15 1

5

tan ) ] (

( ) ( 21

min (C C ) , C 3(15

s s

s au

n n

s r p

s s

z zA z K a

D a D

zK a KP D

S K D z a

z D z z

)

)

)

Deep in 0.175m Deep in 0.875m

Deep in 1.25m

4.2 Bending moment

Strain Bending moment of pile

EIM

D

When the pile is elastic

2 2/EI

M EId y d zD

Get displacement by quadratic integral of bending curvature


-1 0 1 2 3 4 5 6

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Bending moment (kN·m)

Em

be

dd

ed

de

pth

(m

)

2mm

5mm

8mm

10mm

15mm

20mm

25mm

-1 0 1 2 3 4 5 6

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

soil surface

Bending moment (kN·m)

Em

bedded d

epth

(m

) 2mm

5mm

8mm

10mm

15mm

20mm

25mm

PHC-2 PHC-4


-2.5

-2

-1.5

-1

-0.5

0

0.5

-5 0 5 10 15 20

Strain transfermTestingp-y -2.5

-2

-1.5

-1

-0.5

0

0.5

-5 0 5 10 15 20

Strain

m

Test

p-y

-2.5

-2

-1.5

-1

-0.5

0

0.5

-5 0 5 10 15 20

Strain

m

Test

p-y

-2.5

-2

-1.5

-1

-0.5

0

0.5

-5 0 5 10 15 20

Strain

m

Test

p-y

Piles

Piles

Piles Piles

PHC-4

2mm Displacement load




4.3 Displacement comparisons


0 10 20 30 40 502.5

2.0

1.5

1.0

0.5

0.0

-0.5

Earth Surface

Em

bed

ded

Dep

th (

m)

Displacement (mm)

Equation (7)

Test Value

0 10 20 30 40 502.5

2.0

1.5

1.0

0.5

0.0

-0.5

Earth Surface

Em

be

dd

ed

De

pth

(m

)

Displacement (mm)

Equation (7)

Test Value

0 10 20 30 40 502.5

2.0

1.5

1.0

0.5

0.0

-0.5

Earth Surface

Em

bed

de

d D

epth

(m

)

Displacement (mm)

Equation (7)

Test Value

0 10 20 30 40 502.5

2.0

1.5

1.0

0.5

0.0

-0.5

Earth Surface

Em

bedd

ed D

epth

(m

)

Displacement (mm)

Equation (7)

Test Value

（a）10mm Displacement load

（b）15mm Displacement load

（c）20mm Displacement load （d）30mm Displacement load

PHC-4

4.2 New displacement method


6

1i

iTF

iii bPT Z

(0.9 ) 1.25n

ib y D

F

yu

ym

ykP=Pm(y/ym)1

n

PuPm

Pk

b0/60 3b0/80

n

m

my

ypp /1

i )(

mu

muummu

yy

ypypyppp

)()(i

D

zykp khk

Pi

y

4.3 Simple calculation on pile-soil interaction


0 30 60 90 120 1500

5

10

15

Fo

rce

(kN

)

Displacement (mm)

simple calculation method

'p-y' curves method

'm' method

Test

0 30 60 90 120 1500

5

10

15

Fo

rce

(kN

)

Displacement (mm)


'p-y' curves method

'm' method

Test

0 30 60 90 120 1500

5

10

15

For

ce (

kN)

Displacement (mm)


'p-y' curves method

'm' method

Test

0 30 60 90 120 1500

5

10

15

20


'p-y' curves method

'm' method

Test

For

ce (

kN)

Displacement (mm)

（a）PHC-1

（b）PHC-2

（c）PHC-3 （d）PHC-4

4.4 Results comparisons


0 2 4 6 8 103.0

2.5

2.0

1.5

1.0

0.5

0.0

Buri

ed D

epth

(m

)

Displacement (mm)

Test

Calculation

0 5 10 15 20 253

2

1

0

Displacement（mm）

Bur

ied

Dep

th（

m）

Calculation

Test

0 8 16 24 32 403

2

1

0

Bur

ied

Dep

th（

m）


Calculation

Test0 10 20 30 40 50

3

2

1

0

Bur

ied

Dep

th（

m）


Calculation

Test

(a) 10mm Displacement Loading

(b) 25mm Displacement Loading

(c) 40mm Displacement Loading (d) 55mm Displacement Loading

Fan(2014)


(b) 10mm Displacement Load

-0.5 0.0 0.5 1.0 1.53.0

2.5

2.0

1.5

1.0

0.5

0.0

Bur

ial

Dep

th (

m)

bending moment (kN·m)

Calculation

Test

-0.5 0.0 0.5 1.0 1.53.0

2.5

2.0

1.5

1.0

0.5

0.0

Bur

ial

Dep

th (

m)

bending moment (kN·m)

Calculation

Test

(a) 5mm Displacement load

0 15 30 45 600

5

10

15

For

ce (

kN)

Displacement (mm)


'p-y' curves method

'm' method

Test

Fan(2014)

Maximal bending moment locates at 5.0D to 6.0D embedded depth,

concrete of pile cracks around this area primarily.

Degree of prestress and reinforcement ratio has a significant influence

on failure mode of PHC piles.

There are four stages for PHC piles: (1) elastic stage when the

displacement of pile head below 8mm~10mm. (2) Concrete of tensile

zone cracked, which means soil-pile system become elastic-plastic. (3)

Reaching 40mm displacement load, concrete of compressive zone are

out of work, stiffness of pile decreases gradually. After that, soil-pile

separation has a significant influence. (4) failure stage: lateral bearing

capacity drops dramatically.

The test indicate that the distribution law of soil pressure is that with

the change of pile depth, the side earth pressure of pile increased first

and then decreased, and reversed in a certain depth.

5. Conclusion

PHC piles performs a good plastic property and deformation ability

considering soil-pile interaction, which is a suitable type used in IJB.

With the increase of displacement loads, the pressure of shallow soil

grows faster and its maximum is close to the limit passive earth

pressure, while that of the deep soil is relatively slow or even increase

reversely.

It can be seen that the transformation method and the 'm' method to

calculate the horizontal deformation of pile are not accurate for

nonlinear elastic and larger deformation. Although the 'p-y' curves

method takes the non-linear effects of soil into account , there still

exists a large error in calculating the large deformation value.

The horizontal displacement calculation method of pile-soil interaction

that obtained by tests can calculate precisely and accurately the pile

displacement.

5. Conclusion

Thanks for your attention!

THE 3RD INTERNATIONAL JOINTLESS BRIDGES

WORKSHOP

Displacement-based calculation method on soil-pile interaction of PHC...

Documents

Transcript of Displacement-based calculation method on soil-pile interaction of PHC...