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7/29/2019 S8_Pile Driving Analyzer (PDA) and CAPWAP Proven Pile Testing Technology Principles and Recent Advances_LTC2013
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2013 Louisiana Transportation Conference 1
Pile Driving Analyzer (PDA)
and CAPWAPProven Pile Testing Technology:Principles and Recent Advances
Frank Rausche, Ph.D., P.E. Pile Dynamics, Inc.
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Outline Introduction
The PDA History
Basics of PDA testing
Recent developments
Wave Equation Analysis Stresses, damage prevention and detection
Bearing capacity from CAPWAP and iCAP
Vibratory testing and analysis Dynamic pile testing and the LRFD approach
Summary
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Our Objective: to provide the necessary methods,hardware and software for reliable quality assurance of
deep foundations
Pile Dynamics, Inc. -founded in 1972
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1973
1982
1992
19651997
The Pile Driving Analyzer
a long history of improvements
2007
1958
Conforms to
ASTM D 4945
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What is required?Accurate, Reliable and Efficient Pile Top Force and
Velocity Measurements
Reusable lightweightstrain and acceleration
transducers for testing
any pile type
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Accurately calibrated Rugged and Reliable
Allow for self checking
Adapt to any pile type
Cost efficient
Allowing for testingafter-the-fact - when or if
needed
Transducers Requirements
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2 D
Transducer Placement
Traditionally:2 strain sensors +
2 accelerometers.
But frequently we
must use 4 strain
sensors for accuracy!
(large piles, spiral
welded, all drilledshafts/piles, )
7/29/2019 S8_Pile Driving Analyzer (PDA) and CAPWAP Proven Pile Testing Technology Principles and Recent Advances_LTC2013
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Smart, wireless Sensors
calibration transmitted with signal
Sensors
Transmitter
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Sensor-Transmitter Protection
H-piles no issue
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H-piles no issue Pipe piles use protectors
Sensor-Transmitter Protection
7/29/2019 S8_Pile Driving Analyzer (PDA) and CAPWAP Proven Pile Testing Technology Principles and Recent Advances_LTC2013
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Lofting pile into leads
PDA
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H-piles no issue
Pipe piles use protectors
Concrete piles protectors
or - sensors in indentations
Sensor-Transmitter Protection
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Sensor-Transmitter Protection byIndentation
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Pile
SiteA
Pile
Site
B
Pile Driving Analyzer
Engineer
- controls several PDAs
simultaneously as if on-site
- monitors piles in real time
- reports within short time
SiteLink - Remote PDA
Contractor
- schedules easily
- keeps project going
USA Patent #6,301,551
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Soil Borings
Static pile analysis
Pile Type and Length selection
Wave Equation analysis to check driveability Initial Pile Testing program by PDA
Develop driving criterion
Production pile installation to criterion Dynamic testing of production piles as needed
Design and Construction of DrivenPiles*
*See Hannigan et al., 2006. Manual on the Design and Construction of Driven Piles; FHWA
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Wave Equation Analysis (GRLWEAP)
Entersoil profile
Thermodynamic model
predicts stroke for diesels
Predicts Driveability
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Wave Equation Analysis (GRLWEAP)
Updated hammer/driving
system input
Refined capacity vs. blow count after testing
Updated soil parameters
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Finding optimal installation procedure withDynamic Monitoring by Case Method for: Hammer Performance
Driving Stresses
Pile Integrity Soil Resistance at the time of testing
Dynamic Load Testing: Capacity vs. time EoD/BoR setup/relaxation
CAPWAP Signal matching
iCAP Real time signal matching
Dynamic Pile Testing Objectives
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Allowable Driving StressesRelated to pile material strength
For Example, AASHTO provides the following limits:
Steel Piles in Compresssion or Tension:
90% of Steel Yield Strength
Prestressed Concrete Piles in Compression:85% of concrete strength Effective Prestress
Prestressed Concrete Piles in Tension:
Prestress + 50% of concrete tensile strength
Timber - Southern Pine/Douglas Fir:
3.2/3.5 ksi
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Damage Detection
Time of Impact Toe Reflection
Example Records for a Spliced Pile
Bad Pile: Splice should not cause an early reflection
Time of Impact Toe Reflection
Good Pile: No early reflection
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BN 220
Toe Damage Detection: Early Record24 inch PSC L = 56 ft WS 14,000 ft/sec
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BN 260
Toe Damage Detection: First indication24 inch PSC L = 56 ft WS 14,000 ft/sec
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BN 220
7 ft
24 inch PSC L = 56 ft WS 14,000 ft/sec
BN 1094 - EOD
Toe Damage Detection: End of Drive
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CAPWAP - Signal MatchingState-of-practice; required by specs/codes
We know both Input and Response
(wave down and wave up)
This is the information needed to calculatestatic and dynamic soil model parameters
I R
Always (to be) used for capacity calculationfrom dynamic load test
Evaluates stresses vs. depth Models uniform or non-uniform piles
l d l d l
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Pile and Soil Model
Spring (static resistance), i.e.,
Capacity and Distribution
+ Soil Stiffness
Dashpot (dynamic resistance)
Pile Segment
Impedance
Zi = EiAi/ci
l
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CAPWAP Result Summary
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Toe Dynamic Resistance: Measured and CAPWAPGrvare, 1980. Pile Driving Construction Control by the Case Method GroundEngineering.
iff i
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CAPWAPDifferent Users, Static Test
CAPWAP CAPWAPCase
Method
SLT+20%
-20%
CAPWAP Uniqueness? Pretty good
CAPWAP C i i h S i T
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CW versus SLT combined (N=303) (80, 96, SW)
0
10,000
20,000
30,000
40,000
0 10,000 20,000 30,000 40,000
SLT [kN]
CW[kN]
Distribution of CW / SLT Ratios (96&SW: N=226)
0.0%
5.0%
10.0%
15.0%
20.0%
25.0%
unde
r70
70-74
75-79
80-84
85-89
90-94
95-100
101-105
106-11
0
111-115
116-12
0
121-125
126-13
0
over
130
Ratio
Frequency
Distribution of CW / SLTmax Ratios (96&SW: N=179)
0.0%
5.0%
10.0%
15.0%
20.0%
25.0%
unde
r70
70-74
75-79
80-84
85-89
90-94
95-100
101-105
106-11
0
111-115
116-12
0
121-125
126-13
0
over
130
Ratio
Frequency
CAPWAP: Comparison with Static Tests
Conservative
(residual strength)
Unconservative
(potentially unsafe)
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0
100
200
300
400
500
600
700
800
0.000
0.200
0.400
0.600
0.800
1.000
1.200
1.400
1.600
Load(kips)
Displacement(in)
SC test data: T6P1 18 inch solid concrete pile
BOR 7 Day BN 4 (CAPWAP) Static test (14D)
Dynamic: 180 k
end bearing
Static: 176 kend bearing
Superposition
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30 inch
concrete pile
Length 65 ftBlows/
foot
Max. Trans
Energy
Kip-ft
Static Capacity, Kips
Skin
Friction
End
Bearing
Total
Capacity
End of Drive 130 47 198
8801078
Static Load Test 1630
Restrike 120 27 737 228* 965
Superposition 737 880 1617
Superposition:
When Restike is Done with Insufficient Energy
Thus not Activating Full End Bearing
Hussein, M., Sharp, M., Knight, W., The Use of Superposition for Evaluating Pile Capacity,Deep
Foundations 2002, An International Perspective on Theory, Design, Construction, and Performance,
Geotechnical Special Publication No. 116, American Society of Civil Engineers: Orlando, February, 2002
* Not fully activated (low energy)
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Considering Soil Setup Capacity
St. J ohns River Bridge:
Increased loads by 33%with substantially shorter piles
(set-up considered)
Total project:
$110 million (actual)
$20 million (savings)
$130 million (estimate)
Scales & Wolcott, FDOT, presentation at PDCA Roundtable
Orlando 2004
i
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iCAPSignal matching program, executed during monitoring,
i.e., in real time, automatically, for immediate results.
Results:
Total Capacity, with distribution
Load test curve
Compression stresses (max and toe)
Tension stress maximum
Also: Case Damping factor and Match Quality
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iCAP on PDA
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iCAP comparison with CAPWAP (2010)
Pipe Piles H-Piles Concrete Piles
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PDA Testing of Vibratory Driven Piles
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PDA Testing of Vibratory Driven Piles
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.81
-1500
-1000
-500
0
500
1000
1500
0 2 4 6 8 10 12 14 16 18 20
Velocity-
m/s
Force-
kN
Time - L/c (3.7 ms)
Measured - End of Driving
Force Inertia Velocity
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PDA Testing of Vibratory Driven Piles
Soil resistance calculated from
PDA force and velocity testresults based on either power or
force (Case Method) approach
Unfortunately, soil reistance
and bearing capacity often differsignificantly, thus impact restrike
testing still necessary for dynamic
capacity evaluation
GRLWEAP driveabilitypredictions reasonable but
sensitive to assumptions
PDCA LRFD - 2000
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PDCA LRFD - 2000
AASHTO (2010): Rn f1 Q1 + f2 Q2+ .
= 0.50 wave equation analysis (no testing)
0.65 2% or at least 2 dynamic tests0.70 several DOTs specs - dynamic0.75 static or 100% dynamic tests0.80 static and 2% dynamic tests
Load and Resistance Factor Design
PDCA LRFD - 2000
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PDCA LRFD - 2000
Example Calculation:
a) Assume 1.375 average load factorb) Overall factor of safety: FS=1.375/
c) Assume Rn (nominal pile resistance)
of 200 kips
Load and Resistance Factor Design
PDCA LRFD - 2000
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PDCA LRFD 2000
CalculatingOverall safety factor and
No. of piles required for a 2000-kip load
Load and Resistance Factor Design
= 0.50 FS = 2.75 Rn/FS= 72 Npile= 280.65 2.11 (kips) 95 21
0.70 1.96 102 20
0.75 1.83 109 180.80 1.72 116 17
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Reasons for Dynamic Pile Testing
We spend a lot on deep foundations in the USA:$4,000,000,000
We want low risk of failure - remediation is
expensive We want safe bridges and other structures
With LRFD less risk translates into less cost
Testing allows for optimizing a foundation
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Summary: Pile Driving Analyzer
Continuous improvements help obtain moreinformation faster (wireless, remote) and at
lower cost
Test all pile types (steel, concrete, timber) Dynamic pile testing to supplement or replace
static load tests
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Driving stress control to prevent damage
Identify damaged piling
Detect bad hammers for reliable application of
driving crieria
Economical dynamic testing allows for more
tests and higher resistance factors
Summary: Pile Driving Analyzer
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CAPWAP test analysis for reliable capacity
prediction including resistance distribution and
end bearing
40 years experience; large database
Capacity at time of testing (EOD or BOR) forassessment of soil setup
iCAP Signal Matching for operator independent
and immediate results
Summary: CAPWAP
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Thanks for your attention
Frank Rausche
Pile Dynamics, Inc.
www.pile.com