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High Strain Pile Testing with the Pile Driving Analyzer System® (PDA)and CAPWAP®
PDA Wave Mechanics 1
Outline
• Introduction– Measurement Evaluation– Forces and Stresses in Pile– Integrity– Bearing capacity– Examples
• Summary • Problems
PDA Wave Mechanics 2
Measuring strain and accelerationat one point
Strain transducer AccelerometerPDA Wave Mechanics 3
Alternative force transducer or F=ma
For F=ma or top load cell testing, accelerometers must
be attached to pile top.
PDA Wave Mechanics 4
PDA testing and data acquisitionPDA testing and data acquisition
After securely attaching sensors to pile, it is important to input the pertinent and latest calibration values in PDA
PDA Wave Mechanics 5
Measurements on a follower, nearshore
PDA Wave Mechanics 6
The Pile Driving Analyzer - Model 8G
• Measures force and velocity, usually near the pile top, but also at other locations such as the pile toe.
• Determines Case Method resistance, iCAP®, energy transferred to pile and stresses in pile
PDA and CAPWAP 7
Site Link® for Remote MonitoringReduces travel cost and scheduling problems
Site Link® for Remote MonitoringReduces travel cost and scheduling problems
PDA and CAPWAP 8
Acceleration and Strain vs. TimeAcceleration and Strain vs. Time
Accelerometers, one on each side; acceleration, velocity, displacement
Strain Transducers, one on each side; yield strain, stress and average force
PDA Wave Mechanics 9
●
Compressive stresses, forces: FMX, CSX, CSI
PDA Wave Mechanics 10
●CSX = 233 MPa (33.8 ksi)FMX = 1280 kN
●CSX = 233 MPa (33.8 ksi)FMX = 1280 kN
●
● ●CSI = 245 MPa (35.5 ksi)
For H-piles, Load Cell or F=ma Measurements: no CSI
PDA Wave Mechanics 11
Compressive stresses, forces: FMX, CSX, CSI
Force, Velocity, DisplacementForce, Velocity, Displacement
FMX
DMX = ½ max (d1 + d2)
DFN = ½ (d1 fin + d2 fin)
d2(t) = ∫v2(t) dt
d1(t) = ∫v1(t) dt
d1 max
PDA Wave Mechanics 12
d1 fin
d2 fin
Pile top force and velocity from PDAPile top force and velocity from PDA
We are measuring the total force and the total velocityWe plot both together using Z to scale velocity
We are measuring the total force and the total velocityWe plot both together using Z to scale velocity
F(t) = ½ A E [ε1(t) + ε2(t)]
v(t) = ½ [v1(t) + v2(t)] Z
PDA Wave Mechanics 13
Fu = - vu (EA/c)Fu = - vu (EA/c)
u = - vu (E/c)u = - vu (E/c)
εu = - vu / cεu = - vu / cεd = vd / cεd = vd / c
d = vd (E/c)d = vd (E/c)
Fd = vd (EA/c)Fd = vd (EA/c)
If wave travels “downwards”
If wave travels “upwards”
PDA Wave Mechanics 14
Superposition of WavesSuperposition of Waves
Fd=ZvdFd=Zvd
Downward Waves
Fu=-ZvuFu=-Zvu
Upward Waves
F = Fd + Fu
v = vd + vuPDA Wave Mechanics 15
Wave Down and Wave Up from F and Zv
Fd=½(F+Zv) Fu=½(F-Zv)
Fd or Wd; Fu or Wu
Fd1 or Wd1
Fd2 or Wu2
PDA Wave Mechanics 16
If we know wave up and wave downWe can calculate
Pile forces at other locations
If we know wave up and wave downWe can calculate
Pile forces at other locationsThe force at any point along the pile length can be determined from the superposition of the forces in
the upward traveling and downward traveling waves
The force at any point along the pile length can be determined from the superposition of the forces in
the upward traveling and downward traveling waves
F = Fu + FdF = Fu + Fd
PDA Wave Mechanics 17
L
2L/ct = 0 L/c
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/c
PDA Wave Mechanics 18
TopToe
t3
Tension Stress Calculation – Wave-UpTension Stress Calculation – Wave-Up
Point of max tensionmin Fu
min Fu
PDA Wave Mechanics 19
Pile Damage: BTA, LTD
LTD
•A reduction of pile impedance (Z) above the pile toe causes a tension reflection before 2L/c•The time at which the tension reflection arrives at the gage location indicates the depth to Z-reduction: LTD = (tdamage / 2) c
•The magnitude of the Z-reduction is calculated with the -formula
PDA Wave Mechanics 21
t1
t3
Fu,1 = ½(Ft3-Zvt3)
Fd,1 = ½(Ft1+Zvt1)
Damage Example
PDA Wave Mechanics 22
PDA Capacity Monitoring
The 1965 (Phase 1) equation was based on a rigid body model: Ru = F(to) - mp a(to)
Time to is time of zero velocity – no damping
to
PDA Wave Mechanics 23
But then we derived the 1968 Case Method
Resistance WavesL/c
L
x
Ri
-½Ri
RB
RB
Upward traveling wave at time 2L/c:Fu,2 = -Fd,1 + ½Ri + ½Ri + RB
RTL = Fu,2 + Fd,1
Fd,1
-Fd,1
½Ri
PDA Wave Mechanics 24
½Ri
RD = Jv vtoe = Jc Z vtoeRD = Jv vtoe = Jc Z vtoe
Calculated Damping Component
The Case Methoduses the pile toe velocity for damping calculations; it is
affected by shaft and toe soil resistance!
Calculated Damping Component
The Case Methoduses the pile toe velocity for damping calculations; it is
affected by shaft and toe soil resistance!
PDA Wave Mechanics 25
Jv … viscous damping factor [kN/m/s]Jc … the dimensionless Case Damping Factorvtoe = (2Fd1 – RTL)/Z based on wave mechanics
Case Method Static Resistance
Rstatic= RTL - RD
Rstatic= Fu,2 + Fd,1 - Jc(2 Fd,1 – Fd1 – Fu,2)
Rstatic= (1 – Jc)Fd,1 + (1 + Jc )Fu,2
Total Resistance = Static + Dynamic ResistanceTotal Resistance = Static + Dynamic Resistance
PDA Wave Mechanics 26
Fd,1 = 5,450 kN
Fu,2 = 2,730 kN
Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2Rstatic = (1 – Jc) Fd,1+ (1 + Jc) Fu,2
RTL = 5,450 + 2,730 = 8,180 kN
For example with Jc= .3
Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kN
RTL = 5,450 + 2,730 = 8,180 kN
For example with Jc= .3
Rstatic = (1 - .3) 5,450 + (1 + .3) 2,730 = 7,350 kNPDA Wave Mechanics 27
Maximum Case Method Resistance, RXiMaximum Case Method Resistance, RXi
t1 t2
2L/c
Calculates Rstaticat all times after the first velocity peak
Selects the maximum Rstaticfor JC= 0.i
Calculates Rstaticat all times after the first velocity peak
Selects the maximum Rstaticfor JC= 0.i
PDA Wave Mechanics 28
Shaft and Toe Resistance2L/ct = 0 L/c
L
x
R-½R
RB
½R
RB
Fd,1 -Fd,1
½R
PDA Wave Mechanics 29
Ri - Wave upRi - Wave upR
½R
PDA Wave Mechanics 30
An Example: PDA Capacity ResultsEnd of Driving
PDA Wave Mechanics 31
PDA Capacity ResultsRestrike; Blow No. 1
PDA Wave Mechanics 32
Restrike Blow No. 2
PDA Wave Mechanics 33
Restrike, blow No. 4
PDA Wave Mechanics 34
PEBWAP for and End Bearing Pile20x0.5” OEP; LG = 22.3 m; D46-32; 0.6 mm/bl; JC = 0.3
0
1500
3000
4500
6000
7500
0 5 10 15
Res
ista
nce
-kN
Toe Displacement - mm
Total Resistance Static Resistance
Static Resistance = Total Resistance – Damping Factor * Toe Velocity
PDA and CAPWAP 35
THE CAPWAP METHODTHE CAPWAP METHOD
1 Set up pile and soil model and assume
Rshaft and Rtoe
1 Set up pile and soil model and assume
Rshaft and Rtoe
Rshaft
Rtoe
5 If no satisfactory match: Go to Step 25 If no satisfactory match: Go to Step 2
4 Adjust Rshaft and Rtoe4 Adjust Rshaft and Rtoe
3 Compare WUC with measured WUM3 Compare WUC with measured WUM
2 Apply measured WDM to pile model at top and calculate complementary WUC
2 Apply measured WDM to pile model at top and calculate complementary WUC
WUM
WDM
WUC
PDA and CAPWAP 36
First try (poor)
Final match (good)
Adjustments
CAPWAP is an Iterative Process
PDA and CAPWAP 37
Seg. i∆Li
Ri
Fdoi
Fdni
Funi
Fuoi
Rdi
Rui
The Pile is divided in Np
uniform pile segments of approximately 1 m length.
Segment lengths are chosen for equal time increment
∆t = ∆Li/ci.
Each Segment has:
impedance Zi,,= EiAi/ci ,
mass mi = Zi ∆t and
stiffness ki = Zi/∆t .
The Pile Model
PDA and CAPWAP 38
The Combined CAPWAP Pile and Soil ModelThe Combined CAPWAP Pile and Soil Model
Soil segment length:LSi = Nfac Li
Soil segment length:LSi = Nfac Li
Spring (static resistance)Dashpot (dynamic resistance)
Spring (static resistance)Dashpot (dynamic resistance)
t
t
t
t
t
t
t
Pile Model:
Impedance Zi
= EiAi/ci
Pile Segment Length Li
Wave Travel time in Pile t = Li/ci
Pile Model:
Impedance Zi
= EiAi/ci
Pile Segment Length Li
Wave Travel time in Pile t = Li/ci
PDA and CAPWAP 39
Rui, qi
Rt, qt
Ji
JT Shaft Resistance,Ns times
Shaft Resistance,Ns times
tG
The Basic
CAPWAP
Soil Model
The Basic
CAPWAP
Soil Model
End Bearing
End Bearing
PDA and CAPWAP 40
mt
Rui, qi
Rt, qt
Ji
JT
JSK
JBT
Add Radiation DampingInertia Resistance
Add Radiation DampingInertia Resistance
tG
ms
mPL
Some CAPWAP
Soil ModelExtensions
Some CAPWAP
Soil ModelExtensions
mSP
PDA and CAPWAP 41
Signal Matching ExampleSignal Matching Example
PDA and CAPWAP 42
First Trial Analysis (Lousy Match)First Trial Analysis (Lousy Match)
Input F
Matching F
Input F
Matching v
or
Input v
Matching F
or
PDA and CAPWAP 43
Working with Wave-UpWorking with Wave-Up
RU = 782 kips
RT = 68 kips
JS/JT = .05/.15 s/ft
(JCS/JCT = .75/.22)
QS/QT = .10/.12”
RU = 782 kips
RT = 400 kips
RU = 782 kips
RT = 600 kips
RU = 782 kips
RT = 705 kips
JS/JT = .45/.02 s/ft
QS/QT = .10/.12”
PDA and CAPWAP 44
Working with Wave-UpWorking with Wave-Up
RU/RT = 782/705 kips
JS/JT = .45/.02 s/ft
(JCS/JCT = .75/.22)
QS/QT = .10/.12”
RU/RT = 782/705 kips
JS/JT = .30/.05 s/ft
(JCS/JCT = .50/.76)
RU/RT = 782/702 kips
JS/JT = .29/.05 s/ft
(JCS/JCT = .50/.76)
Prev.
PDA and CAPWAP 45
Working with Wave-UpWorking with Wave-Up
RU/RT = 782/702 kips
JS/JT = .29/.05 s/ft
(JCS/JCT = .50/.76)
RU/RT = 765/686 kips
JS/JT = .28/.06 s/ft
(JCS/JCT = .48/.82)
RU/RT = 765/686 kips
JS/JT = .26/.07 s/ft
(JCS/JCT = .44/.97)
QS/QT = .06/.12”
Unloading Parameters
Pretty good match: let’s quitPretty good match: let’s quitPDA and CAPWAP 46
CAPWAP Help FeaturesCAPWAP Help Features
HC
CAPWAP Variable Help
HC
CAPWAP Variable Help
HR
CAPWAP Resistance
vs Displacement Help
HR
CAPWAP Resistance
vs Displacement Help
PDA and CAPWAP 47
CAPWAP’s Static Pile and
Soil Model
CAPWAP’s Static Pile and
Soil Model
kshaft, I = Ru,i/qi
ktoe, i
Ru, i
kp, i
Rtoe, i
Qu1
utoe
PDA and CAPWAP 48
CAPWAP Static AnalysisCAPWAP Static Analysis
The final static load displacement curve is from a t-z and q-z analysis
The final static load displacement curve is from a t-z and q-z analysis
PDA and CAPWAP 49
CAPWAP Static Analysis Options
CAPWAP Static Analysis Options
Smoothing
User Capacity
Uplift Test
Extrapolation
Failure Criteria
Smoothing
User Capacity
Uplift Test
Extrapolation
Failure Criteria
PDA and CAPWAP 50
Standard OutputStandard Output
PDA and CAPWAP 51
Comprehensive CAPWAP ReportComprehensive CAPWAP Report
• “Blow Count” isfrom Direct Input inCAPWAP or fromPDA-W
• “Job Information”provides for otherinformation input
EX1; BENT 17-2; Pile: EX-1 Test: 04-Sep-1991 16:15:D36-23; silt; 16"PSC; Blow: 1171 CAPWAP(R) 2013Beta Version - Pile Dynamics OP: xxx yyyy
Analysis: 28-May-2013
-2500
0
2500
5000kN F Msd
V*Z Msd
5 105 ms
-600
0
600
1200kN
15 L/c
Wup MsdWup Cpt
Pile Type: SteelPile Size: 12 H Pile
Pile Installed: 03-Mar-2013 13:04CAPWAP Capacity: 2677.1 (kN)
at Toe: 376.1 (kN)Set at Yield: 16.897 (mm)Blow Count: 200 b/m
Length: 22.0 (m)Length Bl. gage: 21.9 (m)
Penetration: 21.0 (m)Inclination: 10 (degree)
Hammer: Delmag:D36-23Rated E: 119.3 (kJ)
Transfered E: 30.9 (kJ)Max C Stress Top: 26.2 (MPa)Max C Stress Pile: 26.7 (MPa)Max Ten. Stress: -0.89 (MPa)
0 750 1500 2250 30000.0
7.0
14.0
21.0
28.0
Load (kN)
Displacement (mm)
0.00
5.00
10.00
15.00
20.00
25.00
Depth below Grade (m)
Sand
Sand
Clay
Sand
SPT Nbl/30cm
66
qukPa1000.0
CAPWAPkPa160.0
SoilDescription
Blow Countb/m
221
PDA and CAPWAP 52
EX2; CLARK; SOFT-ROCK; Pile: EX-2 Test: 02-Jun-1993MKT DE 70B, HP 14 X 89; Blow: 627 CAPWAP® 2003-1GRL Engineers, Inc.
CAPWAP FINAL RESULTS
Total CAPWAP Capacity: 764.6; along Shaft 79.5; at Toe 685.1 kips
ft ft kips kips kips kips/ft ksf s/ft in
764.61 6.7 4.2 2.0 762.6 2.0 0.30 0.06 0.255 0.0602 13.5 11.0 1.0 761.6 3.0 0.15 0.03 0.255 0.0603 20.2 17.7 1.0 760.6 4.0 0.15 0.03 0.255 0.0604 26.9 24.4 1.0 759.6 5.0 0.15 0.03 0.255 0.0605 33.7 31.2 2.0 757.6 7.0 0.30 0.06 0.255 0.0606 40.4 37.9 3.0 754.6 10.0 0.45 0.10 0.255 0.0607 47.1 44.6 4.0 750.6 14.0 0.59 0.13 0.255 0.0608 53.8 51.3 18.6 732.0 32.6 2.76 0.59 0.255 0.0609 60.6 58.1 1.0 731.0 33.6 0.15 0.03 0.255 0.06010 67.3 64.8 1.0 730.0 34.6 0.15 0.03 0.255 0.06011 74.0 71.5 1.0 729.0 35.6 0.15 0.03 0.255 0.06012 80.8 78.3 4.9 724.1 40.5 0.73 0.16 0.255 0.06013 87.5 85.0 39.1 685.1 79.5 5.80 1.24 0.255 0.060
Avg. Skin 6.1 0.94 0.19 0.255 0.060
Toe 685.1 503.31 0.066 0.120
Soil Model Parameters/Extensions Skin Toe
Case Damping Factor 0.437 0.971Unloading Quake (% of loading quake) 99 100Reloading Level (% of Ru) 100 100Unloading Level (% of Ru) 78
CAPWAP match quality: 2.88 (Wave Up Match)Observed: final set = 0.050 in; blow count = 240 b/ftObserved: final set = 0.009 in; blow count = 1323 b/ft
Summary Table Output
Summary Table Output
Ri, qi, Ji
PDA and CAPWAP 53
EX2; CLARK; SOFT-ROCK; Pile: EX-2 Test: 02-Jun-1993MKT DE 70B, HP 14 X 89; Blow: 627 CAPWAP® 2003-1GRL Engineers, Inc.
EXTREMA TABLE
Pile Dist. max. min. max. max. max. max. max.Sgmnt Below Force Force Comp. Tens. Trnsfd. Veloc. Displ.No. Gages Stress Stress Energy
ft kips kips ksi ksi kip-ft ft/s in
1 3.4 586.4 -24.4 22.549 -0.937 23.53 11.7 0.7382 6.7 588.7 -24.1 22.635 -0.927 23.40 11.6 0.7254 13.5 585.7 -22.1 22.520 -0.849 22.79 11.5 0.6996 20.2 587.3 -21.1 22.583 -0.810 22.30 11.4 0.6708 26.9 590.1 -19.6 22.691 -0.753 21.73 11.2 0.637
10 33.7 594.8 -18.4 22.870 -0.706 21.02 11.0 0.60011 37.0 592.6 -17.0 22.787 -0.653 20.42 10.9 0.57912 40.4 598.9 -17.2 23.029 -0.661 20.09 10.8 0.55913 43.8 596.6 -15.3 22.940 -0.590 19.39 10.6 0.53914 47.1 607.0 -16.4 23.339 -0.629 19.05 10.4 0.51815 50.5 602.3 -15.2 23.161 -0.585 18.21 10.2 0.49616 53.8 608.4 -15.4 23.393 -0.592 17.79 10.0 0.47317 57.2 568.4 -7.2 21.857 -0.276 15.45 9.9 0.44918 60.6 576.1 -17.7 22.152 -0.682 14.91 9.8 0.42319 63.9 589.0 -27.0 22.650 -1.039 14.16 9.7 0.39420 67.3 624.9 -35.8 24.028 -1.376 13.38 9.6 0.36321 70.7 668.4 -42.0 25.701 -1.613 12.39 9.4 0.32922 74.0 718.3 -48.2 27.622 -1.852 11.36 9.2 0.29323 77.4 756.7 -54.5 29.095 -2.095 10.14 8.8 0.25524 80.8 785.1 -61.7 30.188 -2.371 8.94 8.1 0.21625 84.1 793.0 -61.2 30.492 -2.355 7.59 6.8 0.17826 87.5 806.4 -63.8 31.007 -2.451 6.21 5.3 0.140
Absolute 87.5 31.007 (T = 27.2 ms) 87.5 -2.451 (T = 44.2 ms)
CASE METHOD
J = = 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9RS1 830.3 799.1 767.8 736.6 705.3 674.1 642.9 611.6 580.4 549.2RMX 862.6 839.8 821.8 808.3 795.0 782.0 769.8 757.8 745.7 733.7RSU 836.4 805.8 775.2 744.6 713.9 683.3 652.7 622.1 591.4 560.8
RAU= 595.0 (kips); RA2= 757.7 (kips)
Current CAPWAP Ru= 764.6 (kips); Corresponding J(Rs)= 0.21; J(Rx)=0.64
ft/s ft/s kips kips kips in in kip-ft kips 11.95 0.00 554.8 587.9 587.9 0.747 0.054 23.7 709.9
Numerical Output
Numerical Output
Case Method
Extrema
PDA and CAPWAP 54
TAMPA DRILLED SHAFT TESTING
PDA and CAPWAP 55
Instrumentation
PDA and CAPWAP 56
CAPWAP Results for several blows
0
5000
10000
15000
20000
25000
0 10 20 30 40
Displacement (mm)
Load
(kN
)
Toe Top
APE 750; 60 ton ram (2.4% of test load = 2470 tons). Four blows; 4.5 ft drop; 6 ft dia. shafts; (under pier) in limestonesee: Rausche, Likins, Hussein, (2008). GSP #180, ASCE
Proposed failure criterion for dynamic tests for the cumulative toe displacement: D/60
60 ton ram was 2.4% of failure load
2500 ton failure load
72” dia shaft; Cooper Marl
Large diameter shaft in soil
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 1000 2000 3000 4000 5000 6000
Pile
To
p D
isp
lace
men
t (i
n)
Pile Top Load (Kips)
Blow 3 = 2.5 FT Stroke Blow 4 = 4.0 FT Stroke
Blow 5 = 5.0 FT Stroke Elastic Line
PDA and CAPWAP 58
CAPWAP Comparisons with Static Load Tests – H-Pile
H-pile 14x73 (356 x 109);Penetration 45 mSoil: Silts and clays with N<15 for depths < 30 m, then clays and silts with 40<N<100 to 45 m.Hammer: D30-32EOD: 8 mm set/blowBOR: 5 mm set/blowEOR: 15 mm set/blow
0
500
1000
1500
2000
2500
0 20 40 60 80 100
Displacement (mm)
Lo
ad (
kN)
Top
Toe
SLT
CAPWAP 21-day Restrike (Blow 2): Ru=2060 kN; (Blow 25): Ru=1600 kNStatic Load Test (48 days): 2000 kN; Rausche, Likins, Hussein, 2008.
PDA and CAPWAP 59
Florida Drilled Shaft Florida Drilled Shaft
Diameter:
• to 20 ft (6.1m) 28” (710mm)
• to 44 ft (13.4m) 24” (610mm)
• Soil: Shaft: Sand
Toe: Soft Limestone.
• Hammer: 10 tons
Hussein et al., 1992
6.1 m
13.4 m
Toe 2
Toe
Shaft
Shaft
Note:
Toe 2 treatment much simplified in
CAPWAP 2014
PDA and CAPWAP 60
Florida Drilled Shaft: Class A Prediction Florida Drilled Shaft: Class A Prediction
• Required Rult:
1000 kips (4450 kN)
• Static and dynamic
tests indicate a
capacity less than
760 kips (3380 kN),
depending on criterion
3560 kN
• Offset Criterion yields
650 kips (2890 kN)
from static and
dynamic test.
PDA and CAPWAP 61
CAPWAP Correlation: Automatic ProcedureCAPWAP Correlation: Automatic Procedure
PDA and CAPWAP 62
CAPWAP Correlation:Radiation Damping Model
CAPWAP Correlation:Radiation Damping Model
PDA and CAPWAP 63
Combined Data Bases of GRL 1996and from Stress Wave Conferences
Mean: 0.98; COV: 0.17; N = 303
Likins and Rausche, 2004PDA and CAPWAP 64
CAPWAP Critique - iCAP Features
• CAPWAP is Non-unique?Just one result!
• CAPWAP is Slow?Real time result!
• CAPWAP needs Experience?Done by PDA Operator!
PDA and CAPWAP 65
iCAP Application• When?
– During Monitoring– During Restrike– During Reanalysis
• When Not?– When pile and/or soil properties are not well known– Problem data which lead to poor matches
• How?– Just turn it on
• Notes:– iCAP can be run directly from CAPWAP-2014 for non-
uniform piles– iCAP is no CAPWAP; differences must be expected;
review is recommended
66PDA and CAPWAP 66
Summary
• PDA Testing During Driven Pile installation, called monitoring, checks driving stresses, pile integrity, resistance at the time of testing
• Performing a resike test after waiting yields a dynamic load test.
• Case Method closed form measurements together with stress wave considerations yield information on – dynamic stresses
– pile integrity
– bearing capacityPDA Wave Mechanics 67
The EndQuestions?
PDA Wave Mechanics 68
The Second End
No more questions?
PDA Wave Mechanics 69