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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
PDPI June 2015 – PDA and Case Method 3
PDA Testing Objectives:
Economical Load TestingPDA Testing Objectives:
Economical Load TestingDynamic Testing Static Testing
PDPI June 2015 – PDA and Case Method 4
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)
PDPI June 2015 – PDA and Case Method 5
Dynamic Pile Testing ApproachDynamic Pile Testing Approach
PDPI June 2015 – PDA and Case Method 6
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
PDPI June 2015 – PDA and Case Method 7
Mounting the sensorsMounting the sensors
PDPI June 2015 – PDA and Case Method 8
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
PDPI June 2015 – PDA and Case Method 10
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
PDPI June 2015 – PDA and Case Method 13
SiteLink and Wireless Testing
Makes also for happy contractors and clients
PDPI June 2015 – PDA and Case Method 14
• 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
PDPI June 2015 – PDA and Case Method 15
Measurements on a follower, nearshoreMeasurements on a follower, nearshore
PDPI June 2015 – PDA and Case Method 16
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
PDPI June 2015 – PDA and Case Method 17
Standard PresentationStandard Presentation
F = ½ (S1 + S2 ) (EM * AR)
v = ½ ∫(a1 + a2 ) dt
Fu = ½ (F - vZ)
Fd = ½ (F + vZ)
PDPI June 2015 – PDA and Case Method 18
Maximum Force, FMX
PDPI June 2015 – PDA and Case Method 19
●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)
PDPI June 2015 – PDA and Case Method 20
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
PDPI June 2015 – PDA and Case Method 21 PDPI June 2015 – PDA and Case Method 22
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
PDPI June 2015 – PDA and Case Method 23
Tension Stress Maximum and DistributionTension Stress Maximum and Distribution
t3
toptoe
Point of max tension
Max. Tension Wave Up
Equal
PDPI June 2015 – PDA and Case Method 24
Another Tension Stress ExampleAnother Tension Stress Example
toptoe
PDPI June 2015 – PDA and Case Method 25
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
PDPI June 2015 – PDA and Case Method 26
PDPI June 2015 – PDA and Case Method 27
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
PDPI June 2015 – PDA and Case Method 28
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
24 inch PSC L = 56 ft WS 14,000 ft/sec
BN 260BN 220
24 inch PSC L = 56 ft WS 14,000 ft/sec
Toe Damage Detection: End of Drive
7 ft
PDPI June 2015 – PDA and Case Method 33
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
PDPI June 2015 – PDA and Case Method 34
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
PDPI June 2015 – PDA and Case Method 35 PDPI June 2015 – PDA and Case Method 36
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!)
PDPI June 2015 – PDA and Case Method 37
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.
PDPI June 2015 – PDA and Case Method 38
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
PDPI June 2015 – PDA and Case Method 39
Tensile downward wave
Fdr = -½R; vdr = -½R/Z
R/2
PDPI June 2015 – PDA and Case Method 40
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
PDPI June 2015 – PDA and Case Method 41
Wave-up Force Change Due to FrictionWave-up Force Change Due to Friction
RfRf
½Rf
PDPI June 2015 – PDA and Case Method 42
PDA Soil Resistance ResultsEnd of Driving
PDA Soil Resistance ResultsEnd of Driving
PDPI June 2015 – PDA and Case Method 43
PDA Soil Resistance ResultsRestrike; Blow No. 1
PDA Soil Resistance ResultsRestrike; Blow No. 1
PDPI June 2015 – PDA and Case Method 44
Restrike Blow No. 2Restrike Blow No. 2
PDPI June 2015 – PDA and Case Method 45
Restrike, Blow No. 4Restrike, Blow No. 4
PDPI June 2015 – PDA and Case Method 46
PDPI June 2015 – PDA and Case Method 47
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
PDPI June 2015 – PDA and Case Method 51
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
PDPI June 2015 – PDA and Case Method 53
Cylinder Piles 66” dia.Cylinder Piles 66” dia.
PDPI June 2015 – PDA and Case Method 54
PDA Measurements
including circumferential strain measurements!
PDA Measurements
including circumferential strain measurements!
PDPI June 2015 – PDA and Case Method 55
Cylinder Pile Data (EOD)Cylinder Pile Data (EOD)
PDPI June 2015 – PDA and Case Method 56
PDPI June 2015 – PDA and Case Method 57
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
PDPI June 2015 – PDA and Case Method 64
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)
PDPI June 2015 – PDA and Case Method 65
GRLWEAP Static Soil Analysis
GRLWEAP Static Soil Analysis
• Based on “SA” analysis using:• N-value• qu
Ru = 1700 kNRshaft = 1200 kN
PDPI June 2015 – PDA and Case Method 66
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
PDPI June 2015 – PDA and Case Method 67
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)
PDPI June 2015 – PDA and Case Method 68
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
PDPI June 2015 – PDA and Case Method 70
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
PDPI June 2015 – PDA and Case MethodPDPI June 2015 – PDA and Case Method 71
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
PDPI June 2015 – PDA and Case Method 72
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
PDPI June 2015 – PDA and Case MethodPDPI June 2015 – PDA and Case Method 75
Thank you for your attention
For further information see: www.pile.com
QUESTIONS?
Thank you for your attention
For further information see: www.pile.com
QUESTIONS?
PDPI June 2015 – PDA and Case Method 76