GeoRadar Division IBIS range PRODUCTS APPLICATIONS · GeoRadar Division IBIS-FS measured scenario...
Transcript of GeoRadar Division IBIS range PRODUCTS APPLICATIONS · GeoRadar Division IBIS-FS measured scenario...
GeoRadar Division
Static and Dynamic Monitoring of Civil Engineering Structures by Microwave
Interferometry
Garry Spencer and Mark Bell
1
GeoRadar Division
LANDSLIDE & DAM MONITORINGIBIS - FL
SLOPE STABILITY IN MININGIBIS - FM
STRUCTURE MOVEMENTSIBIS - FS
IBIS rangeAPPLICATIONSPRODUCTS
2XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
GeoRadar Division
XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
3
GeoRadar Division
IBIS FS Hardware
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Techniques behind the IBIS FS system
1. Frequency Modulated - Continuous Wave (FM-CW) technique for obtainingthe 1-Dimensional Range Profile with Range Resolution.
The IBIS FS product utilises two radar techniques:
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17.1 – 17.3 GHz
Single Transmit & Receive Burst
2. Interferometric technique
GeoRadar Division
The interferometric analysis provides data on object displacement bycomparing phase information, collected in different time periods, of reflectedwaves from the object, providing a measure of the displacement with anaccuracy of less than 0.01mm (intrinsic radar accuracy in the order of 0.001mm.)
Interferometric Technique
TX
RX
TX
RX
d
TX
RX
TX
RX
d
First acquisition
Second acquisition
1ϕ
2ϕ
( )124ϕϕ
πλ −−=d
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GeoRadar Division
The displacement is measured in the direction of the line of sight of the system.
Rh
d
dp
α
h
Rdd p ⋅=
R
h=)sin(α)sin(α
pdd =
To calculate the real displacement is needed to know the acquisition geometry
The distance Ris measured
by IBIS-S
1-D Interferometric technique
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June 2014
GeoRadar Division
IBIS-FS measured scenario is determined by
• Antenna beamwidth (depending on the model, from 10° to 50°).
• User’s defined maximum range (up to 1 Km)
The measured scenario is divided into range bins, whose number depends on the range resolution (0.75 m minimum, constant with distance). Two targets at the same distance from the radar fall on the same range bins.
IBIS
-FS
n-thrange bin
Range profile
Distance (m)
IBIS-FS Acquisition Mode
Range resolution
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GeoRadar Division
IBIS-FS installed at the turbine pillar base (height 60m)
Welding lines are good reflective points
Range Profile: one dimensional image with 0.5m range resolution
IBIS-FS: 1-dimensional range profiles
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Measurement accuracy: IBIS vs. Total Station
Test objective: comparison between IBIS-S results and a high-performance TotalStation in measuring a target displacement
Target distance: 33mForced displacement:• 3 x 1mm step towards IBIS-S and -3mm back• 2 x 0.5mm step towards IBIS-S and -1mm back• 5 x 0.1mm step towards IBIS-S and -0.5mm back
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Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
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Measurement accuracy : IBIS vs. Total Station
0 500 1000 1500 2000-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
time [sec]
Rad
ial D
ispl
acem
ent [
mm
]1mm displacements
1 mm displacement
-0,0035
-0,0030
-0,0025
-0,0020
-0,0015
-0,0010
-0,0005
0,0000
0,0005
0 20 40 60 80 100 120
Measure Number
Dis
plac
emen
t (m
)
0 200 400 600 800 1000-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
time [sec]
Rad
ial D
ispl
ace
men
t [m
m]
0.5 mm displacement
0,5 mm displacement
-0,0015
-0,0010
-0,0005
0,0000
0,0005
60 80 100 120 140 160 180
Measure Number
Dis
plac
emen
t (m
)
IBIS-S results Total station results
1mm
ste
ps0.
5mm
ste
ps
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0 500 1000 1500 2000 2500 3000 3500 4000 4500
-0.50
-0.40
-0.30
-0.20
-0.10
0.00
0.10
time [sec]
Rad
ial D
ispl
acem
ent [
mm
]
0.1 mm displacement
0,1 mm displacement
-0,0008
-0,0005
-0,0003
0,0000
0,0003
120 140 160 180 200 220 240 260 280 300 320 340 360 380 400
Measure Number
Dis
plac
emen
t (m
)
IBIS-S results Total station results
0.1m
m s
teps
Measurement accuracy : IBIS vs. Total Station
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Static Monitoring
Load positionCorners
IBIS-FS
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IBIS-FS corner reflectors
BEAMS
CORNERREFLECTORS
From the structure plan is possible to determine whether reflectors are needed or not.
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0 10 20 30 40 50 60 7030
40
50
60
70
80
90CB
G
HD
EF
A
SNR
(dB
)
Ground-Range (m)
Range profile of P2-S – P3-S span
IBIS-FS installation
Bridge testing: static live load test
: Linear Variable Differential Transformer to measure displacement
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LVDT
0 200 400 600 800 1000 1200 1400-30
-20
-10
0
10
B D F H
disp
lace
men
t (m
m)
time (s)
LC1
Bridge testing: static live load test
: Linear Variable Differential Transformer
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LVDT
0 200 400 600 800 1000 1200 1400-30
-20
-10
0
10 IBIS-S LVDT
-20.50-15.62
-8.84
disp
lace
men
t (m
m)
time (s)
LC1
Bridge testing: static live load test
: Linear Variable Differential Transformer
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GeoRadar Division
P1P3 P4
P2
Static settlements of bridge’s pier and beam
5 m6,5 m
P4
P3
P2
P1
-0,6
-0,5
-0,4
-0,3
-0,2
-0,1
0
0,1
0,2
0 500 1000 1500 2000 2500 3000 3500 4000
tempo [s]
spos
tam
ento
[mm
]
P1
P2
P3
P4
Vertical movements of the 4 points
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Dynamic Monitoring
Corners
IBIS-FS
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Measurement objective: comparison with accelerometers, resonancefrequencies and modal shape retrieval
Central arch length (m): 62.5
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Dynamic Monitoring: Capriate bridge
GeoRadar Division
To make a comparison between theresults of IBIS-S system andaccelerometers system 6 corner reflectorwere installed at the same position ofaccelerometers
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June 2014
Dynamic Monitoring: Capriate bridge
GeoRadar Division
Bridge photograph and range profile
22XXV International Federation of Surveyors
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Dynamic Monitoring: Capriate bridge
GeoRadar Division
Velocity comparison for Test Point 22
Vel
ocity
[mm
/sec
]V
eloc
ity [m
m/s
ec]
Time [sec]
Time [sec]
IBIS-S
accelerometer
Zoom on the first 15 sec – direct comparison
IBIS-S
acc
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Dynamic Monitoring: Capriate bridge
GeoRadar Division
Frequency analysis comparison on
3000sec acquisition duration
IBIS- FS
acc
Acc detected frequency
IBIS-S detected frequency
Percentage error
Hz Hz %
2,617 2,595 0,84
3,164 3,182 -0,57
6,641 6,608 0,50
8,086 8,077 0,1124XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
Dynamic Monitoring: Capriate bridge
GeoRadar Division
f = 2.617 Hz
f = 6.641 Hz f = 8.086 Hz
f = 3.164 Hz
Modal shape obtained by accelerometer data
Dynamic Monitoring: Capriate bridge
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Modal shapes comparison
0 23 46 69 92 115-1.2
-0.6
0.0
0.6
1.2 Accelerometer IBIS-S sensor
Nor
mal
ized
Mod
e S
hape
Distance along deck (m)
0 23 46 69 92 115-1.2
-0.6
0.0
0.6
1.2 Accelerometer IBIS-S sensor
Nor
mal
ized
Mod
e S
hape
Distance along deck (m)
f=2.617Hz
f=3.164Hz
Dynamic Monitoring: Capriate bridge
26XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
GeoRadar Division
f=6.641Hz
f=8.086Hz
0 23 46 69 92 115-1.2
-0.6
0.0
0.6
1.2 Accelerometer IBIS-S sensor
Nor
mal
ized
Mod
e S
hape
Distance along deck (m)
0 23 46 69 92 115-1.2
-0.6
0.0
0.6
1.2 Accelerometer IBIS-S sensor
Nor
mal
ized
Mod
e S
hape
Distance along deck (m)Modal shapes comparison
Dynamic Monitoring: Capriate bridge
27XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
GeoRadar Division
XXV International Federation of Surveyors
Congress, Kuala Lumpur, Malaysia, 16 – 21
June 2014
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In Summary: • Interferometry deflection measurements were measured
and compared with accelerometer and Linear VariableDifferential Transformer fully validating the instrumentresults.
• The IBIS-FS can be rapidly deployed for short-termdisplacement and vibration monitoring with completemeasurement and set up time being less than one hour
• A great deal of information can be captured from a numberof points on a variety of structures very quickly making theunit an excellent alternative for economical static anddynamic surveys
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Questions ?
Thanks for your attention