© 2014 pile dynamics, inc. pdpi june 2015 – pda and case ... · pdpi june 2015 – pda and case...

2015Frank Rausche Pile Dynamics, Inc.

The Case Method and the Pile Driving Analyzer® (PDA)

PDPI June 2015 – PDA and Case Method 1© 2014 Pile Dynamics, Inc.

Outline• Testing Objectives

• Hardware– Standard

– Wireless testing

– Remote testing

PDPI June 2015 – PDA and Case Method 2

• Methods− Stresses− Integrity− Capacity− Energy

• Examples• Summary


PDA Testing Objectives:

Economical Load TestingPDA Testing Objectives:

Economical Load TestingDynamic Testing Static Testing


PDA Testing Objectives: Installation MonitoringResults for every hammer blow

PDA Testing Objectives: Installation MonitoringResults for every hammer blow

• Stresses• At location of sensors• Maximum tension stress• Pile toe stresses

• Pile Integrity (impedance change)• Soil Resistance

• At the time opf testing (EOD or BOR)• Shaft resistance estimate

• Hammer Performance• Energy transferred to pile• Stroke of diesel hammers

Basically we have to measure Pile Top Force and Pile Top Velocity.

Then we have to process the data with the Pile Driving Analyzer® System (PDA)

Basically we have to measure Pile Top Force and Pile Top Velocity.

Then we have to process the data with the Pile Driving Analyzer® System (PDA)


Dynamic Pile Testing ApproachDynamic Pile Testing Approach


Measuring Strain and Acceleration (need to do it on opposite pile sides)Measuring Strain and Acceleration (need to do it on opposite pile sides)

Strain transducer Accelerometer

PDA testing data acquisitionPDA testing data acquisition• Need Minimum 2 strain measurements per pile to

compensate for bending


Mounting the sensorsMounting the sensors


Alternative force transducer or F=maAlternative force transducer or F=ma

For F=ma or top load cell testing, accelerometers must

be attached to pile top.PDA Wave Mechanics 9

Strain and Acceleration SensorsStrain and Acceleration Sensors

Wireless Under Water


Sensor Installation/ProtectionSensor Installation/ProtectionH-piles Pipe piles H-piles Pipe piles

PDPI June 2015 – PDA and Case Method 11 PDPI June 2015 – PDA and Case Method 12

Lofting a test pileLofting a test pile

Smart and Wireless Sensors Make for Happy Testers

Smart and Wireless Sensors Make for Happy Testers


SiteLink and Wireless Testing

Makes also for happy contractors and clients


• No traveling/scheduling cost/delays/issues

• Immediate analysis and quick report submittal

• Increased efficiency of test engineer

• Remote supervision of inexperienced personnel avoids errors

SiteLink Advantages


Measurements on a follower, nearshoreMeasurements on a follower, nearshore


Basic Strain and Acceleration MeasurementsBasic Strain and Acceleration Measurements

ε1(t), ε2(t), one strain on each side

a1(t), a2(t), one acc. on each side


Standard PresentationStandard Presentation

F = ½ (S1 + S2 ) (EM * AR)

v = ½ ∫(a1 + a2 ) dt

Fu = ½ (F - vZ)

Fd = ½ (F + vZ)


Maximum Force, FMX


●CSX = 233 MPa (33.8 ksi)●

● ●CSI = 245 MPa (35.5 ksi)

Calculated at Bottom: CSB = 264 MPa (38.2 ksi)

Compresisve Stress Results At Gage Location (CSX and CSI) and at Bottom (CSB)


Calculating Tension Stresses Below Pile TopFrom Force in Wave-down and Wave-up

Calculating Tension Stresses Below Pile TopFrom Force in Wave-down and Wave-up

Fd

Fu

F

vZ


L

Upward Wave

Upward Wave

Downward

Wave

Downward

Wave

Wave Superposition for Force Below SensorsWave Superposition for Force Below Sensors

x

Fd1

Fu2

Fx = Fu2 + Fd3

Fd3

2x/ct = 0

2L/c

L/c

Tension Stress Calculation (Wave-Up)Tension Stress Calculation (Wave-Up)

Fu

Fd

Max. Tension - up

Minimum Compression - down

x


Tension Stress Maximum and DistributionTension Stress Maximum and Distribution

t3

toptoe

Point of max tension

Max. Tension Wave Up

Equal


Another Tension Stress ExampleAnother Tension Stress Example

toptoe


Pile Damage: BTA, LTDPile Damage: BTA, LTD

A pile impedance reduction (damage?) causes a tension reflection before 2L/c

The time at which the tension reflection arrives at the gage location indicates the depth to the damage: LTD = (tdamage / 2) c



2L/ct = 0 L/c

Z2

Fd2

Fu1

Fd,1

2x/c

Z1

A

B

FA = FB: Fu,1 + Fd,1 = Fd,2

vA = vB: vu,1 + vd,1 = vd,2

2nd equation: (Z2/Z1)(Z1vu,1 + Z1vd,1) = Z2 vd,2

with = Z2/Z1: (- Fu,1 + Fd,1) = Fd,2 = Fu,1 + Fd,1

= (Fu,1 + Fd,1) / (- Fu,1 + Fd,1)

x

‐ Formula Derivation ‐ Formula Derivation

t1

t3

Fu,1 = ½(Fu,t3 - Zvt3)

Fd,1 = ½(Ft1+Zvt1)

Damage Assessment ExampleDamage Assessment Example


Damage Detection: Spliced pile Example

Time of Impact Toe Reflection

Good Pile Bad Pile: Early reflection

Time of Impact Toe Reflection

BN 220

Toe Damage Detection: Early Record

24 inch PSC L = 56 ft WS 14,000 ft/sec

Toe Damage Detection: First Indication


BN 260BN 220


Toe Damage Detection: End of Drive

7 ft


Resistance WavesResistance Waves

L/c

L

x

Ri

-½Ri

RB

½Ri

RBUpward traveling wave at time 2L/c:

Fu,2 = -Fd,1 + ½Ri + ½Ri + RB

Fd,1 -Fd,1

½Ri

RTL = Fu,2 + Fd,1

Fu,2

Fd,1


The Case Method EquationThe Case Method Equation

RTL = Fd,1 + Fu,2 RTL = Fd,1 + Fu,2

RTL is the total pile resistance:Dynamic + static; shaft resistance + end bearing

RTL is mobilized during time 2L/c following time t1

RTL is the total pile resistance:Dynamic + static; shaft resistance + end bearing

RTL is mobilized during time 2L/c following time t1

The Static Resistance is Total Resistance ‐ DampingThe Static Resistance is

Total Resistance ‐ Damping

RS= RTL – RDAssumingRD = Jv v [kN/m/s][m/s]

Introducing: Jc = Jv / Z ….. Case Damping Factor

Then RD = Jc Z v

Introducing: Jc = Jv / Z ….. Case Damping Factor

Then RD = Jc Z v


Using pile toe velocity as representativevtoe = 2 Fd,1‐ RTL

Using pile toe velocity as representativevtoe = 2 Fd,1‐ RTL

Rstatic= RTL - Jc(2 Fd,1 – RTL)

Rstatic= (1 – Jc)Fd,1 + (1 + Jc )Fu,2

vtoe

Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2

F= 5450 kN

F= 50 kN

F =2,820 kN

F = 2,730 kN

RTL = 5,450 + 2,730 = 8,180 kN

For example with Jc= 0.3

Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kN (5,450 for J=1!)

RTL = 5,450 + 2,730 = 8,180 kN

For example with Jc= 0.3

Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kN (5,450 for J=1!)


Time of Fd,1 and Fu,2Time of Fd,1 and Fu,2

t1 t2 2L/c

We calculate Rstatic at the time when it gives the maximum activated (mobilized) resistance value.

We calculate Rstatic at the time when it gives the maximum activated (mobilized) resistance value.


RMX

R

Compressive upward wave

Fur = ½R; vur = -½R/ZR/2

∆x

x

Pile with shaft resistance:Equilibrium and ContinuityPile with shaft resistance:Equilibrium and Continuity


Tensile downward wave

Fdr = -½R; vdr = -½R/Z

R/2


Shaft and Toe ResistanceShaft and Toe Resistance2L/ct = 0 L/c

L

x

Rf-½Rf

RB

½Rf

RB

Fd,1

-Fd,1 ½Rf

Friction Pile RecordsFriction Pile Records

Fd Fu

F

vZ


Wave-up Force Change Due to FrictionWave-up Force Change Due to Friction

RfRf

½Rf


PDA Soil Resistance ResultsEnd of Driving

PDA Soil Resistance ResultsEnd of Driving


PDA Soil Resistance ResultsRestrike; Blow No. 1

PDA Soil Resistance ResultsRestrike; Blow No. 1


Restrike Blow No. 2Restrike Blow No. 2


Restrike, Blow No. 4Restrike, Blow No. 4



Calculating the Transferred Energy

WR

hWR

Max ET = ∫F(t) v(t) dtENTHRU

ηT = ENTHRU/ ER

transfer ratioER = WRh

Manufacturer’s RatingMeasure Force, F(t)Velocity, v(t)

Statistical Summaries for SA–Air/Steam HammersTransfer Ratios at End of Driving

Hammer Performance

48

Concrete Piles: N=194Steel Piles: N=747

Mean 67% Mean 41%

Statistical Summaries for Diesel Hammers Transfer Ratios at End of Driving

Hammer Performance

49

Concrete Piles; N=668Steel Piles; N=1419

Mean 39% Mean 29%

Statistical Summaries for Hydraulic Hammers Transfer ratios at End of Driving

Hammer Performance

50

Mean 69% Mean 49%

Concrete Piles; N=67Steel Piles; N=203


Fre

quen

cy P

erce

nt

Transfer Ratio

Frequency of transfer ratios forSA Air/Steam, Diesel DA Air/Steam, Hydraulic

Frequency of transfer ratios forSA Air/Steam, Diesel DA Air/Steam, Hydraulic

Tra

nsf

er R

atio

Transfer Ratio: Average 0.35, COV 0.17

Hammer Performance

52

Hammer Energy VariationsSame Hammer, Same Site at EOD for 42 Piles

Hammer Energy VariationsSame Hammer, Same Site at EOD for 42 Piles

• Hammer was a D19‐42 OE diesel

• Steel H‐piles; EOD

• Claystone bearing layer

• Hammer energy appeared not related to driving resistance

Rausche et al., 2008. Mastering the art of dynamic pile testing, SWC Kuala Lumpur

Expected Mean: 39%

A Monitoring Example: Rigolet Bridge


Cylinder Piles 66” dia.Cylinder Piles 66” dia.


PDA Measurements

including circumferential strain measurements!

PDA Measurements

including circumferential strain measurements!


Cylinder Pile Data (EOD)Cylinder Pile Data (EOD)



Case Method Monitoring ResultsCase Method Monitoring ResultsExample: 914 mm (36") dia. Jacket leg pile Example: 914 mm (36") dia. Jacket leg pile

Length: 92 m

Required Penetration: 70 m

Hammer: Vulcan 530 (13.5 Mg x 1.5 m)

Concern: Damage due to CalcareniteLayer

Example: Soil DescriptionExample: Soil Description PDA Display: prior to hard driving (39.0 m)PDA Display: prior to hard driving (39.0 m)

PDA Display: Highest Driving Resistance (39.3 m)PDA Display: Highest Driving Resistance (39.3 m)

GRLWEAP ENTHRU 119 kJ

Installation blow counts and stressesInstallation blow counts and stresses

Range of Rock

GRLWEAP Top Stress 144 – 153 MPa

Installation blow counts and stressesInstallation blow counts and stressesBlows/0.25 m

Pile top stress ~ MPa

Range of Rock

A 24” Square PSC Pile Example A 24” Square PSC Pile Example

Size: 610 mm (24”) with 270 mm (10.5”) circular void Length: 20.5 m (67.25’)Depth: 14 m (45.9’)Hammer: D 30‐32 Diesel hammer; Er = 102 kJ (75.4 k‐ft)

Wr = 29.4 kN (6.6 kips); hr = 3.45 m (11.3 ft)Hammer Cushion: A = 2680 cm2; E = 3790 Mpa; t = 90 mm

A = (415 in2); E = (550 ksi); t = (3.5”); COR=0.8HelmetWeight: 35.4 kN (7.76 kips)PileCushion: Oak Boards, 230 mm (9”) thickness


A Concrete Pile: Wave equation + Testing

Water Table at 3 m or 10’ depth

Depth Description N qu

m (ft) kPa (ksf)

4 (13) Sand 6

8 (26) Sand 13

13.4 (44) Clay 180 (3.8)

22 (72) Clay with Sand Lenses 300 (6.2)


GRLWEAP Static Soil Analysis

GRLWEAP Static Soil Analysis

• Based on “SA” analysis using:• N-value• qu

Ru = 1700 kNRshaft = 1200 kN


Wave Equation analysis: Bearing Graph

At refusal (1210 bl/m or 370 bl/ft) we would expect 4000 kNcapacity at a stroke of 2.5 m and a transferred energy of 26.8 kJ


GRLWEAP at Refusal

1210(370)

27(20)

17.5(2.5)

1.1(0.15)

PDA Results and Comparison GRLWEAPPDA Results and Comparison GRLWEAP

PDA Wave Equation Rated/MeanStroke in m

in ft2.7 8.8

2.58.3

3.511.3

Transfer Ratio(%) 21 27 29

Blow Count

Transf’d Energy

Comp.Stress

Tension Stress

Bl/m (Bl/ft)

kJ(ft-kips)

MPa(ksi)

MPa(ksi)

Measured 1460(445)

21(15.5)

13.5(1.9)

2.4(0.35)


Summary of Capacities Based on EODSummary of Capacities Based on EOD

Static Analysis Capacity

ActualBlow Count

Wave Equation Capacity

CAPWAP Capacity

kN (kips)

Bl/m (Bl/ft)

kN(kips)

kN(kips)

1,700 (382)

1482 (445)

4,000 (900)

2,100(470)

Check whether additional capacity can be gained with time by doing a restrike test.

Pile is driven 6 inches after 24 hours waiting time.Blow Count now is 300 Bl/m (90 bl/ft)

PDPI June 2015 – PDA and Case MethodPDPI June 2015 – PDA and Case Method 69

Hammer Performance ResultsEnd of Drive (445 Bl/ft)

Hammer Performance ResultsEnd of Drive (445 Bl/ft)

PDA Wave Equation Rated/MeanStroke in m

in ft2.7 8.8

2.58.3

3.511.3

Transfer Ratio(%) 21 27 (Refusal) 29

Beginning of 24 hr Restrike (90 Bl/ft)PDA Wave Equation Rated

Stroke in min ft

3.3 10.7

2.58.3

3.511.3

Transfer Ratio(%) 35 26 (90 bpf) N/A


Capacity Summary Based on EOD and BORCapacity Summary Based on EOD and BOR

Static Analysis Capacity

ActualBlow Count

Wave Equation Capacity

CAPWAP Capacity

kN (kips)

Bl/m (Bl/ft)

kN(kips)

kN(kips)

End of Driving

1482 (445)

4,000* (900)

2,100**(470)

Restrike1,700***

(382)300 (90)

2,500(560)

2,550570


Capacity and (LRFD) Safe Load SummaryCapacity and (LRFD) Safe Load Summary

Method

Nominal Resistance

(kN)

Resistance Factor, φ(AASHTO 2009)

Equivalent F.S.

Equ.Safe Load

(kN)

Static Formula 1700 0.40 (avg) 3.50 485

ENRGates

31,3524,510

0.100.40

14.03.50

2,2401,290

WE-EODWE-BOR

4,0002,500

0.500.50

2.802.80

1,430890

CW-EODCW-BOR

2,1002,550

0.650.65

2.152.15

9771,190


Taking Advantage of Soil Setup

Nominal or Required Capacity is RREQ (say 400 tons)

Determine End of Drive Capacity from Monitoring, REOD (say450 tons)

Find out Restrike Capacity, RBOR (say 550 tons)

Setup Factor is fSETUP = RBOR/REOD (550/450=1.22)

Drive Pile at EOD to fSETUP * RREQ (400/1.22=328 tons)

Demonstrate Adequacy by Restrike Testing

Soil Setup

St. Johns River Bridge:

Increased loads by 33% with substantially shorter piles (set-up considered)

Total project cost:

• $130 million (estimate)

• $110 million (actual)

• $20 million (savings)

Scales & Wolcott, FDOT, presentation at PDCA Roundtable Orlando 2004

• The PDA processes pile top force and velocity records according to the (closed form solution) Case Method; results allow for assessment of • Pile Stresses• Hammer Performance• Soil Resistance• Pile Integrity

• These results are diplayed in Real Time and, therefore, allow for real time monitoring of the pile installation

• For Dynamic load testing Restrikes + CAPWAP are usually necessary

• After PDA+CAPWAP the GRLWEAP analysis can be refined

SummarySummary


Thank you for your attention

For further information see: www.pile.com

QUESTIONS?

[email protected]

Thank you for your attention

For further information see: www.pile.com

QUESTIONS?

[email protected]


© 2014 pile dynamics, inc. pdpi june 2015 – pda and case ... · pdpi june 2015 – pda and case...

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