embedded data collector piles estimation of pile tip...

Embedded Data Collector Piles

Estimation of Pile Tip and Skin Capacities in Real Time

David Sadler, P.E.Construction Engineer

Florida Department of Transportation

Acknowledgements:Dr.Michael McVay, Professor, University of FloridaDon Robertson, P.E., Applied Foundation Testing

Richard Hecht, Smart Structures Inc.John Farrell, P.E., FDOT

Dr.Sastry Putcha, P.E., FDOT

Current Technology:

Expensive Gages Are AttachedAfter The Pile Leads Are InPlace And Removed Prior ToThe Leads Being Removed

To Attach And Detach TheGages Someone Must ClimbThe Leads

Does Not Provide A ReliableEstimate Of Pile Toe Capacity

Data Acquisition System AndAnalysis Software AreComplicated (i.e. multiple software) And Require A Highly Experienced User

Analysis Software Does NotProvide A Unique Solution

SensorAntenna

Battery Pack

Data AcquisitionAntenna

Data AcquisitionSystem

New Technology:

Strain Gage

Accelerometer

New Technology:

Antenna

Battery and Transmitter / ReceiverNew Technology:

Real-Time Capacity Calculations

Force – Velocity Top of Pile

Wave Up - Wave Down

Force – Velocity Toe of Pile Pile Displacements

New Technology:

Fd,top = (Pt1 +ZVt1)/2

Fd,toe = (Pt2 +ZVt2)/2

STR = Tip/Skin =(Fd,toe )/(Fd,top - Fd,toe)

( )[ ]

( )[ ]1 1 2 2

1 12 2

STATIC c c

P ZV P ZVR J J

− −= − + +

Total Pile Capacity [Canadian Geotech, 2001]

Static Pile Capacity -Based on Case Damping, JcL,Determined from Ratio of Total (static +damping) Resistance/Toe Resistance,[Can. GeoTech J. 2001]

Pile Tip Capacity: When pile tip velocity attains zero value,

damping forces become zero. The corresponding pile tip force

becomes the static tip resistance.

Pile Tip Force Pile Tip Velocity

Static Pile tip capacity variation

Static+Damping Force variation

Inertial +Static+Damping Forcevariation

I-95 @ Moncrief Creek

Bent 1 Pile 2

Compression Stress (Top of Pile) Comparison

0.0

0.5

1.0

1.5

2.0

2.5

3.0

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Co

mp

res

siv

e S

tre

ss

- T

op

of

Pile

(k

si)

PDI PDA Embedded Data Collector

Stop To Remove TemplateResume Driving

Stop to Change Cushion

Resume Driving

End of Drive

Begin Drive


Bent 1 Pile 2

Compression Stress (Bottom of Pile) Comparison

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Co

mp

res

siv

e S

tre

ss

- P

ile

To

e (

ks

i)

Embedded Data Collector (Measured) PDI PDA (Computed)

Stop To Remove Template

Resume Driving


Resume Driving

End of Drive

Begin Drive

Tensile Stress CalculatedUsing Top Gages Only.Significant ImprovementMay Be Realized UsingTop And Toe Gages.


Bent 1 Pile 2

Maximum Computed Tension Stress Comparison

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Te

ns

ile

Str

es

s -

Ma

xim

um

Co

mp

ute

d (

ks

i)

Embedded Data Collector PDI PDA


Resume Driving


Resume Driving

End of Drive

Begin


Bent 1 Pile 2

Maximum CASE Capacity (Jc=0.4) Comparison

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

550.0

600.0

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Ma

xim

um

CA

SE

Ca

pa

cit

y (

kip

s)



Resume DrivingStop to Change Cushion

Resume Driving

End of Drive

Begin Drive


Bent 1 Pile 2

Maximum CASE Capacity (Jc=0.4) Comparison

-80.0

-70.0

-60.0

-50.0

-40.0

-30.0

-20.0

-10.0

0.0

0 100 200 300 400 500 600

Maximum CASE Method Capacity (kips)

Pile

De

pth

(fe

et)



Bent 1 Pile 2

Total Capacity

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

550.0

600.0

650.0

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Ult

ima

te P

ile

Ca

pa

cit

y (

kip

s)

UF Total Capacity


Resume Driving


Resume Driving

End of Drive

Begin Drive


Bent 1 Pile 2

Pile Tip Capacity

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

20:09:36 20:24:00 20:38:24 20:52:48 21:07:12 21:21:36 21:36:00

Time

Tip

Ca

pa

cit

y (

kip

s)

UF Tip Capacity


Resume Driving


Resume Driving

End of Drive

Begin Drive

I-95 at Edgewood

Static Pile Load Test

Strain Measurement Comparison

-50

0

50

100

150

200

250

300

350

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000

Time (seconds)

Str

ain

(u

e)

Level 1 B Average Level 2 Average Level 5 EDC Top Strain EDC Toe Strain

Pile Top

Pile Tip

I-95 at Edgewood

Load Test Pile

Load versus Displacement

-1.8

-1.6

-1.4

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0 50 100 150 200 250 300 350 400 450

Load (kips)

Dis

pla

ce

me

nt

(in

ch

es)

AVERAGE DISPLACEMENT FDOT Failure Criteria FDOT Failure Criteria 2

O Ring Failure, Test Stopped

I-95 @ Edgewood

Load Test Pile

Tip Capacity Comparison

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

10:39:22 10:40:05 10:40:48 10:41:31 10:42:14 10:42:58 10:43:41 10:44:24 10:45:07

Time

Tip

Ca

pa

cit

y (

kip

s)

UF Tip Capacity Static Test

I-95 @ Edgewood

Load Test Pile

Capacity Comparison

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

10:39:22 10:40:05 10:40:48 10:41:31 10:42:14 10:42:58 10:43:41 10:44:24 10:45:07

Time

Ult

ima

te P

ile

Ca

pa

cit

y (

kip

s)

UF Total Capacity Static Test Failure Load

End Bearing Comparison

-500%

-400%

-300%

-200%

-100%

0%

100%

200%

300%

400%

500%

600%

700%

800%

900%

1000%

CAPWAP

(Pre

dic

ted

Tip

-M

ea

su

red

Tip

) /

(Me

as

ure

d T

ip)x

10

0

Over-prediction

Under-prediction

LA 1 Results

Costs• The overall goal is to

achieve the lowest unit cost possible while maximizing the number of piles that can be tested

• By testing more piles:

– lower safety factors or

higher LRFD φ factors can

be utilized

– overall foundation costs can be reduced

– project safety and confidence are moved to a higher level

Costs• Expect typical electronics economies of scale: Higher

performance at Lower cost over time

• Expect continued innovations in wireless and sensors further driving costs down

• Have an initial chicken-egg challenge at the introduction of this capability (e.g. CD players initially cost $1K at their introduction

2005

2006

2007

2008

< 100

< 500

< 5000

> 5000

$-$100$200$300$400$500$600$700

$800

$900

$1,000

$1,100

$1,200

Approximate Cost

Year

Volume

SmartPile™ Year-over-YearEmbedded Data Collector Costs

FDOT Costs Of Testing

Jan 2003 – Jan 2005 Test Piling Average Bid Prices

Pile Size – 24” Prestressed Concrete

Test Pile $174 per LF

Production Pile $43 per LF

$110 increase per foot

x 100 foot pile

$11,000 for Test Pile

Dynamic Load Test $1,654 Each

$12,654 per 100 LF Test Pile

Summary and Conclusions

• Embedded Strain and Acceleration Measurements - Compare favorably with current External Attachment Method at pile top – In Addition Embedded Provide Real Time Tip Measurements

• Static Testing - Embedded Strain Measurements Taken During The Static Load Test At The Pile Top And Pile Tip Compared Favorably With The Strain Measurements Made With The Sister Bar Strain Gages Used During The Static Load Test

• Reliable - The System Has Been Demonstrated To Reliably Collect Data Before (on site), During (whole drive) and After (e.g. load test) Pile Installation Process

• Better Capacity Estimates - Total And Tip Resistance are Computed Individually For Every Hammer Blow In Real Time

• Advanced Capabilities - Additional Information Can Be Uploaded And Stored On The Pile In The Casting Yard And Downloaded By The System Operator At The Project Site

• Safety - Safety Is Improved Dramatically By Removing The Need To Climb The Pile Leads To Attach Gages

• Time Savings - Dramatic Time Savings (Contractor, CEI, & Owner) At The Project Site Can Be Realized By Eliminating The Need To Prepare The Pile In The Field, Attach And Detach The Gages, As well as Climbing The Pile Leads

Future Growth

Monitoring System

Wireless Telemetry

Information Services•Remote Monitoring•Data management•Reporting/Query•Analysis

Structures with 100’s of embedded

sensors

Finished Structures

ContractorsCivil Engineers

Government Agencies

Internet

• FHWA

• State DOTs

• FEMA

• Other

•Multi-user with access control•Web accessible•Mobile user accessible (PDA, smart phone, etc.)

Continuous Remote Structural Monitoring

embedded data collector piles estimation of pile tip...

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