A Macro-element for Pile Head

Response to Cyclic Lateral

LoadingPresenter:

Norazzlina M.Sa’don

Co-Authors:

M.J. Pender, R.P. Orense & A.R. Abdul Karim

Dept. Civil & Environmental Eng., The University of Auckland, Auckland

205 April 2009

CONTENTS

INTRODUCTION

OBJECTIVES

PILE-SOIL INTERACTION

PREDICTION OF SINGLE PILE RESPONSE

CONCLUSIONS

305 April 2009

INTRODUCTION

Laterally Loaded Piles

Active

Loading applied at its top,

i.e. bridges, high-rise building,

overhead sign and piers.

Passive

Loading applied along its length

due to earth pressure,

i.e. piles in moving slope or

secant-pile wall.

Dynamic pile-soil interaction subjected to static anddynamic lateral response:

The non-linear behaviour of the soils at high strain levels

The slippage and development of gap between pile andsurrounding soil near the ground surface

Cyclic degradation of soil stiffness and strength

The energy dissipation (damping) in the soil

Winkler Model (1867)Soil pressures acting on the piles

can be modelled by independent

non-linear springs

Matlock et al. (1978), Novak et al.

(1978), and Reese and van Impe,

(2001)

Brom’s Method (1964)Considering both the ultimate

strength of the bearing ground &

the yield stress of the pile material.

Analytical Methods

Elastic Continuum Model (1936)Analytical homogeneous continuum

approach - the continuity of the soil

mass

Model is based on Young’s modulus

of the soil, Es

Poulos (1971a, b)

Finite Element MethodsRequires large computational

effort in the discretisation of the

pile and the surrounding soils.

Blaney et al. (1976) and

Kuhlemeyer (1979)

605 April 2009

Lateral Cyclic Pile-Soil ResponseVarious types of hysteresis loops: S-shaped loops to oval-shaped loops.

Typical hysteresis loops from different cyclic and seismic pile load tests

(after Allotey and El Naggar, 2008)

705 April 2009

OBJECTIVES

To use a simple set of equations for pile head stiffness

Macro-element

to demonstrate an analytical method for the cyclic response of the

laterally loaded pile as an alternative to computer software packages

LPILE – Reese and van Impe, 2001 and

RUAUMOKO – Carr, 2005

to compare with the cyclic Winkler calculations and field data

obtained from published results

805 April 2009

Elastic Continuum Model (ECM)

PILE-SOIL INTERACTION MODEL

0 E(z)

z

Es

(a) Constant

s sD

zE E

D

0 E(z)

z

D

(b) Linear (c) Square root

s sD

zE E

DD

0 E(z)

z

905 April 2009

Pile embedded in homogeneous soil - over-consolidated clays.

Static linear lateral response of a single pile

Nonlinear lateral response of a single pile

H

u θ

e

1005 April 2009

Non-linear hysteresis curve for cyclic loadingModelling of pile-soil interaction (Masing’s rule)

Backbone curve

Hysteresis loop

(after Ishihara 1990)

1105 April 2009

Austin (Reese et al. 1975)

Case Study 1

Pile A

OD = 625 mm

EpIp =138 MNm2

Stiff fissured clay

Es/su = 500

A B

Pile B

OD = 170 mm

EpIp = 3 MNm2

H H

1205 April 2009

(a) 625 mm pile

(b) 170 mm pile

(after Reese et al. 1975)

0

20

40

60

80

100

0 4 8 12

u : mm

H:

kN

MeasuredProposed methodp-y analysis

(a) 625 mm pile

(b) 170 mm pile

0

20

40

60

80

100

0 4 8 12

u : mm

H:

kN

MeasuredProposed methodp-y analysis

1305 April 2009

Bagnolet (Kerisel 1965)

Case Study 2

Medium stiff clay

Dia. = 0.43 m

EpIp = 255 MNm2

H

1405 April 2009

0

20

40

60

80

100

0 4 8 12

u : mm

H:

kN

MeasuredProposed methodp-y analysis

1505 April 2009

The nonlinear response at the top of the

pile shaft subjected to cyclic lateral

loading was evaluated.

Pile head projection:

Case 1 – 1 OD

Case 2 – 2 OD

Case 3 – 4 OD

Assumption:

The pile is fully elastic below the

yield moment.

PREDICTION OF SINGLE PILE

RESPONSE

X

Y

z

0 E(z)

E=Es

P

OD = 273.1 mm

WT = 12.7 mm

Ep = 200 GPa

su = 100 kPa

Es/su = 300

= 0.5

1605 April 2009

Results

Computed values of load-displacement for Case 1

150 120 90 60 30 0 30 60 90 120 150200

150

100

50

0

50

100

150

200

Displacement (mm)

Pile

Head

Load

(kN

)

1705 April 2009

Results

Computed values of load-rotation for Case 1

200 150 100 50 0 50 100 150 200

200

100

100

200

300

Rotation (mrad)

Mom

ent (

kN

m)

MOUT

MOUT1

MOUT2

MOUT3

MOUT4

OUT OUT1 OUT2 OUT3 OUT4

200 160 120 80 40 0 40 80 120 160 200200

150

100

50

0

50

100

150

200

Rotation (mrad)

Pile

Head

Load

(kN

)

1805 April 2009

Results

Comparison of load-displacement for all cases

Force-displacement curve

-150

-100

-50

0

50

100

150

-100 -50 0 50 100

Displacement, u (mm)

Fo

rce,

H (

kN

)

1-OD

2-OD

4-OD

1905 April 2009

The application of a simple set of pile stiffness equations to analyseboth linear and non-linear pile-soil interaction.

The Davies and Budhu equations provided a convenient way tomodel the pile-soil behaviour.

The good agreement with the results of full-scale tests suggestedthat the elastic-plastic continuum model is an appropriate approachto the laterally loaded pile problem.

The objective of developing a simple tool and an independent wayof checking available software are working correctly was achieved.

CONCLUSIONS

A Macro-element for Pile Head

Response to Cyclic Lateral

LoadingN. M.Sa’don, M.J. Pender, R.P. Orense & A.R. Abdul Karim

Dept. Civil & Environmental Eng.,

The University of Auckland, Auckland,

New Zealand.

2105 April 2009Sources: www.wikipedia.org

New Brighton Piers, Christchurch

Auckland Harbour Bridge, Auckland Sky Tower, Auckland

2205 April 2009

Pile embedded in homogeneous soil - over-consolidated clays.

Static Linear Lateral Response of a Single Pile

Nonlinear Lateral Response of a Single Pile

y uy E

y y E

u I u

I u

E UH UM

E H M

u f H f M

f H f M

H

u θ

e 0.18 0.45 0.73

2 3

1.3 2.2 9.2; ; and uH uM H M

s s s

K K Kf f f f

E D E D E D

0.2 0.2 0.2

0.45 0.33 0.29

2.9 2.9 2.91 ; 1 ; and 1

10.5 12.5 20uy y My

h k h k h kI I I

k k k