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
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
I-95 @ Moncrief Creek
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
Stop to Change Cushion
Resume Driving
End of Drive
Begin Drive
Tensile Stress CalculatedUsing Top Gages Only.Significant ImprovementMay Be Realized UsingTop And Toe Gages.
I-95 @ Moncrief Creek
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
Stop To Remove Template
Resume Driving
Stop to Change Cushion
Resume Driving
End of Drive
Begin
I-95 @ Moncrief Creek
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)
Embedded Data Collector PDI PDA
Stop To Remove Template
Resume DrivingStop to Change Cushion
Resume Driving
End of Drive
Begin Drive
I-95 @ Moncrief Creek
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)
Embedded Data Collector PDI PDA
I-95 @ Moncrief Creek
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
Stop To Remove Template
Resume Driving
Stop to Change Cushion
Resume Driving
End of Drive
Begin Drive
I-95 @ Moncrief Creek
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
Stop To Remove Template
Resume Driving
Stop to Change Cushion
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