View
4
Download
0
Category
Preview:
Citation preview
ADVANCED DYNAMIC LOAD TESTING METHODS –PRESTRESSED CONCRETE PILESIndependent Tip and Skin Capacities
Aneesh Goly, Ph. D., P.E.
Director of Engineering & Operations
Smart Structures
Sastry Putcha, Ph. D., P.E.
Vice President
Smart Structures
Presented by:
Advanced DLT Methods – Prestressed Concrete Piles | 2
Dynamic Testing Methods of Analysis & Advancements
1968
Case Method Only Total
Resistances using Top Gauges
Signal Match Analysisfor estimation of Tip & Skin Resistanceson a single Blow
1970
EDC
Introduction2003
UF Method - Total & Tip Resistances
using Top & Tip Gauges for all Blows
2013
FDOT Method – Independent Tip & Skin Resistances
using Top & Tip Gauges for all Blows
DLT 1.0
DLT 2.0
DLT 3.0
Top only External Instrumentation
Introduction
Advanced DLT Methods – Prestressed Concrete Piles | 3
Top Only External Gauges
Advanced DLT Methods – Prestressed Concrete Piles | 4
Top only External Gauges
Picture Courtesy: RADISE INTERNATIONAL
Accelerometer
Strain
Transducer
Advanced DLT Methods – Prestressed Concrete Piles | 6
Top and Tip Gauges – Embedded Data Collectors (EDC’s)
Advanced DLT Methods – Prestressed Concrete Piles | 7
• Electronics/Sensors (strain and
accelerometer) Embedded in the pile core
at both pile ends…
• Wireless Communication and Data
Transmission from the pile
• Ruggedized Workstation to Collect Sensor
Data in Real Time
• SmartPile Software provides real-time
measured data - capacities, stresses and
integrity
• Data Portal to organize and share results
Embedded Data Collectors (EDCs)
SmartPile Workstation
Tip Gages
L
Top Gages
Internet
Wireless Data
Network
Advanced DLT Methods – Prestressed Concrete Piles | 8
Wireless DataPort (flush mounted)
SmartPile Engineering
Workstation
Sensor Pack – Pile Top
(with combined accelerometer, temp. and strain sensing)
Sensor Pack – Pile Tip
configurable up to 3 Sensor Packs
total/system
500 foot range…
Universal Installation Bracket makes
installation quick and simple
Typical Configuration for Driven Piles
Top
Tip
Advanced DLT Methods – Prestressed Concrete Piles | 9
Top and Tip Embedded Data Collectors (EDC’s)
Accelerometer
Positioning
FrameworkStrain Gauge
Accelerometer
Positioning
Framework
Strain Gauge –
centered in pile
core
Advanced DLT Methods – Prestressed Concrete Piles | 10
Top and Tip Embedded Data Collectors (EDC’s)
Advanced DLT Methods – Prestressed Concrete Piles | 11
Top and Tip Embedded Data Collectors (EDC’s)
DLT 1.0 – CASE METHOD AND SIGNAL MATCH ANALYSIS (TOP ONLY)
Advanced DLT Methods – Prestressed Concrete Piles | 13
Case Method
• Only estimates Total axial capacity based on arbitrary damping factor value
1000
800
600
400
200
0
-200
-400
Case Method, Total Capacity =
(1 – Jc)[F1 + Z X V1]/2 + (1 + Jc) [F2 – Z X V2]/2
Jc = ?
DLT
1.0
Advanced DLT Methods – Prestressed Concrete Piles | 14
Case Method: Damping Factor Values
Gravel 0.3 0.4
Sand 0.4 0.5
Clay 0.7 1.0
Silt 0.5 0.7Reducing
Grain Size
Increasing
Damping
factor
DLT
1.0
DLT 2.0 – UF METHOD OF ANALYSIS(TOP AND TIP SENSORS)
Advanced DLT Methods – Prestressed Concrete Piles | 19
UF Method
The UF method utilizes both top and tip sensor packs to predict total and tip static capacities
• Total Capacity = Total Static Capacity from Case equation with Dynamic
Jc from Top and Tip gages for every blow
• Tip Capacity = Tip static capacity from Unloading Point based on Tip
gages
• Skin Capacity = Total Capacity – Tip Capacity
Tip Gages
L
Top Gages
DLT
2.0
Advanced DLT Methods – Prestressed Concrete Piles | 20
UF Method: Total Capacity
…calculated using top and tip gauges
Dynamic Damping, Jc = - 0.09744 x In (Tip / Skin) + 0.2686
UF Method, Total Capacity = (1 – Jc)[F1 + Z X V1]/2 + (1 + Jc) [F2 – Z X V2]/2
DLT
2.0
Limin Zhang, Michael C. McVay, and Charles W. W. Ng (2001), “A possible physical meaning of Case damping in pile dynamics”, Candian Geotechnical Journal, Vol 38.
Advanced DLT Methods – Prestressed Concrete Piles | 21
UF Tip Capacity: Unloading Point Method
At point where Fstatnamic is maximal (point 1):c = [Fstatnamic – Fstatic – (ma)tip]/vtip
At unloading point (point 2):
Fstatic = Fstatnamic – (ma)tip
DLT
2.0
Advanced DLT Methods – Prestressed Concrete Piles | 22
UF Skin Capacity
• The University of Florida Capacity
method uses the Total Capacity
calculated using the Dynamic Jc and the
Tip Dynamic Unloading Capacity.
• Skin Capacity = Total Capacity – Tip
Capacity
DLT
2.0
DLT 3.0 – FDOT METHOD OF ANALYSIS (TOP AND TIP SENSORS)
Advanced DLT Methods – Prestressed Concrete Piles | 24
• FDOT method determines the independent static tip and skin resistances in near real time
on every blow by analysing the data from the top and tip sensor packs embedded in the
pile.
• Tip Resistance values are evaluated based on conservation of energy method. Applied
energy as recorded in the tip gauge = static + damping + inertial energies recorded in
the tip gauge
• Skin Resistance is evaluated based on segmental skin friction method with Top & Tip
gauge data as the boundary conditions
• Total Resistance = Mobilized Tip Resistance + Mobilized Skin Resistance
FDOT Method of Analysis - Independent Tip and Skin Resistances DLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 2525
• Knowing tip conditions (end-bearing or floating
piles)
• The pile segment beneath the tip gages and the
soil below the tip moving together is considered
a single degree of freedom system (SDOF).
• The measured tip force from the strain gage is
the external force applied to the system. Since
the applied force is measured directly, the tip
analysis is independent of the skin analysis.
• Tip static force (tip resistance) can be accurately
extracted directly from the measured dynamic
force.
Tip Gages
L
Top Gages
SDOF Applied force(strain gage)
FDOT Method: Tip ResistanceDLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 26
“Estimating static tip resistance of driven piles with bottom pile instrumentation” , Tran, McVay, Herrera, and Lai, Canadian Geotechnical
Journal, Vol 49., April 2012
Energy Method For Accessing Damping and Static forces
DLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 27
• Model the pile tip as a SDOF
• Nonlinear stiffness k
• Model updating by Genetic
Algorithm
Displacement, u(x,t)
Sta
tic
Tip
Res
ista
nce
k
Max(u)
1
k2
k3
k4
l1 l3l = Max(u)- l - l2 1 3
A
B
Max(u)/2
range 1
Max(u)/2
range 2
Tran K.T., McVay M., Herrera R., and Lai P. (2012), “Estimating Static
Tip Resistance of Driven Piles with Bottom Pile Instrumentation”,
Canadian Geotechnical Journal
FDOT Method: Tip ResistanceDLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 28
EDC Blow 777 Forces vs. Time at Pile Tip of Pier 8 Pile-300.00
-200.00
-100.00
0.00
100.00
200.00
300.00
400.00
500.00
600.00
700.00
-0.01 7E-17 0.01 0.02 0.03 0.04 0.05
Fo
rce
(kip
s)
Time (sec)
Inertia Force
Static Resistance
damping force
applied force
predicted gage force
Where damping
and inertia forces
are zero, static
force is equal
to applied force.
0 0
Force & Energy Method For Accessing Damping and Static forces
DLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 29
Dixie Highway 24” x 50’
0
200
400
600
800
1000
1200
1400
1600
0 5 10 15 20 25 30
Sta
tic
Tip
Re
sist
an
ce (
kN
)
Displacement (mm)
Blow 1
Blow 2
Blow 3
Blow 4
Blow 5
Static LoadTest
Matching Forces: Inertia, Damping & Static
FDOT Method - Tip Resistance: Florida pile
Zero velocity point
Dynamic = Static
DLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 30
Knowing boundary conditions at both ends of a pile
helps simulate wave propagation along the pile
accurately
• The difference between top and tip downward
forces is the dynamic side friction, which is the sum
of static side friction and side damping
• Static side friction can be accurately extracted from
the dynamic side friction.
)()(1
0),0(
straintgx
u
xattv
)()(2
),(
straintgx
u
lxattlv
Side friction
Side damping
FDOT Method: Skin ResistanceDLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 31
B
Cc
B
fb
Ea
where
bt
uc
t
u
x
ua
srs 44
.
2
2
2
2
22
qKf
and
unloadingfortxuuKf
qtxuwithloadingforf
qtxuwithloadingfortxuK
f
u
u
us
)],()[max(
),(
),(),(
Tran K.T., McVay M., Herrera R., and Lai P. (2012), “Estimation of Nonlinear Static Skin Friction on Multiple Pile Segments Using Measured Hammer Impact Response at the Top and Bottom of the Pile”,
Computers and Geotechnics
Model 1-D wave propagation in pile
FDOT Method: Skin ResistanceDLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 32
0 2 4 6 8 10 12 14 16 18 200
100
200
300
400
500
600
700
800
Displacement, mm
Skin
Fric
tio
n, kN
segment 4
segment 2
segment 3
segment 1
total
Displacement, u(x,t)
Loading
Quake q
Un
it S
kin
Fri
ctio
n, fs
Ult
imat
e U
nit
Sk
in F
rict
ion
, fu
KK
Max(u)
Seg
men
t le
ng
th
Lm
To
tal
pil
e le
ng
th, L Fs,m
Fd,m
)()(1
0),0(
straintgx
u
xattv
)()(2
),(
straintgx
u
lxattlv
FDOT Method: Skin Resistance
• Model updating by Genetic Algorithm
• Matching estimated to measured particle velocities at top and bottom of pile
DLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 33
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07-1
0
1
2
3
Time, s
Top
Ve
locity, m
/s
Observed
Estimated
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07-1
0
1
2
3
Time, s
Botto
m V
elo
city, m
/s
Observed
Estimated
Skin Friction of Dixie Highway, Pile 1
0
100
200
300
400
500
600
700
800
900
1000
0 2 4 6 8 10 12 14 16 18 20 22 24
Displacement, mmS
kin
Fric
tio
n, k
N
Blow 1
Blow 2
Blow 3
Blow 4
Blow 5
Load Test
0 20 40 60
0
2
4
6
8
10
12
14
0 20 40 60
SPT 'N'
De
pth
, m
Ultimate unit skin friction, kN/m2
a) Dixie Highway, pile 1
blow 1
blow 2
blow 3
blow 4
blow 5
SPT
Finesand
Cemented sand & shell
0 20 40 60
0
2
4
6
8
10
12
14
0 20 40 60
SPT 'N'
De
pth
, m
Ultimate unit skin friction, kN/m2
b) Dixie Highway, pile 2
blow 1
blow 2
blow 3
blow 4
blow 5
SPT
Cemented sand & shell
Finesand
Dixie Highway 24” x 50’
FDOT Method - Skin Resistance: Florida PileDLT
3.0
Advanced DLT Methods – Prestressed Concrete Piles | 44
www.smart-structures.com
Aneesh Goly, Ph.D., P.E.
Email: agoly@smart-structures.com
Presented by:
4152 W Blue Heron Boulevard
West Palm Beach, Florida 33404
Phone: (561) 988-0070
Email: info@smart-structures.com
Sastry Putcha, Ph.D., P.E.
Email: sputcha@smart-structures.com
Recommended