s8_pile driving analyzer (pda) and capwap proven pile testing technology principles and recent...

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, )



Smart, wireless Sensors

calibration transmitted with signal

Sensors

Transmitter



Sensor-Transmitter Protection

H-piles no issue



H-piles no issue Pipe piles use protectors




Lofting pile into leads

PDA



H-piles no issue

Pipe piles use protectors

Concrete piles protectors

or - sensors in indentations




Sensor-Transmitter Protection byIndentation



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



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



Wave Equation Analysis (GRLWEAP)

Entersoil profile

Thermodynamic model

predicts stroke for diesels

Predicts Driveability



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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-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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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


PDCA LRFD - 2000


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PDCA LRFD 2000

CalculatingOverall safety factor and

No. of piles required for a 2000-kip load


= 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

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