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Model Updating for SMART Load Rating of Bridges. Chang-Guen Lee / Won-Tae Lee Korea Expressway Corporation Jong-Jae Lee / Young-Soo Park Sejong University, Korea. Controlled or Blocked Traffic. Measuring Deflection or Strain. Why Load Carrying Capacity? - PowerPoint PPT Presentation
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Model Updating for SMART Load Rating of Bridges
Chang-Guen Lee / Won-Tae LeeKorea Expressway Corporation
Jong-Jae Lee / Young-Soo Park
Sejong University, Korea
Smart Load Rating of Bridges Using Ambient Acceleration Data
Why Load Carrying Capacity?• Increase of the Number of Deteriorated Bridges• Prognosis of Remaining Lives• Widely Used as an Index for Bridge Integrity
Conventional Load Rating Test
Conventional loading tests
Controlled or Blocked Traffic
Measuring Deflection or Strain
Inconvenient & Increase of logistics cost A lot of time & cost for field tests
Load Carrying Capacity of a Bridge (MOCT, 2005, Korea)
Pr : Design live load : DB-24 (43.2tonf)*
RF : Rating factor by static analysis using the initial FE modelKd : the deflection correction factor - by static loading tests
Ki : the impact correction factor - by dynamic loading tests
Kr, Kt : the other correction factors - empirically estimated
*DB-24 : Korean design code for highway bridge about 1.3 times of HS-20, AASHTO
r r tP P RF K K δ iKK
Deteriorated bridges
SMART Load Rating
Correction of FE modelusing dynamic characteristics of
bridges
Conventional methodusing truck loading tests
Correction of analysis results using static deflection (strain) data
Advantages• No need to control or block traffics• Easier to measure acceleration rather than strain/deflection• High reliability by continuous measurements• Less time- and labor-consuming
Deflection Correction Factor (Kδ)
*Other Correction Factors – Empirically Estimated (usually 1.0)
initial FEManalysisproposedupdated FEManalysis
K
initial FEM
analysis
measured
K
Conventionalmodel
updating Proposed
Advantages
Procedures
3 6
T i m e3 6
T i m e3 6
T i m e
Updated FE model
Simulation of truck loading tests
Ambient vibration tests Model updating Load Rating
Modal parameter ID
Evaluation of Load Carrying CapacityModal Parameter Identification
Updating Initial FE Model
Estimation of Deflection Correction
Factor (Kδ)
Initial FE model
Measuring Ambient Acceleration
Modal Analysis
Planning of Vibration Tests
Updated FE modelAnalysis = Exp. ModesYesNo
Ambient acceleration data excited by ordinary traffic on a bridge without traffic control are measured. Based on the modal properties extracted from the ambient vibration data, the initial finite element (FE) model of the bridge can be updated to represent the current real state of a bridge. Using the updated FE model, the deflection akin to the real value can be easily obtained without measuring the real deflection. Based on the deflection values from initial and updated FE models, deflection correction factor can be obtained.
Procedure 1
Experimental modal analysis has drawn lots of attention from structural engineers for updating the analysis model and estimating the present state of structural integrity. Ambient vibration tests under wind, wave, or traffic loadings may be effective for large civil-infra structures. Several modal parameter identification methods without using input information in the frequency and the time domain are available, such as Frequency Domain Decomposition (FDD) and Stochastic Subspace Identification (SSI), etc.
0 20 40 60 80 1000
5
10
15
20
25
30
Frequency(Hz)
Mo
de
l o
rd
er
1st singular values
Stable mode
Unstable mode
Noise mode
SV functions in FDD
Stabilization Chart in SSI
Modal Parameter ID Using Ambient Vibration Tests
FE Model Updating
Using the extracted modal properties, the initial FE model is updated using various kinds of optimization algorithms. The objective function can be constructed using the differences between the measured and estimated natural frequencies, and the constraint equations were considered to limit the differences between the measured and estimated mode shapes as
2
1min | |
m c mNc mi i
i ji jimi i
f fJ w subjected to
f
Downhill Sim-plex
Genetic Algo-rithms
Procedure 2
Proof Tests
Yeoju JCT Test Road
25 PCC Test Sections2830m
15 AC Test Sections2710m
OfficeGeumdang
Br.Yeondae
Br.Samseung
Br.Yeoju JCT Test RoadTest Road
25 PCC Test Sections2830m
15 AC Test Sections2710m
25 PCC Test Sections2830m
15 AC Test Sections2710m
OfficeGeumdang
Br.Yeondae
Br.Samseung
Br.
Ordinary Expressway
Korea Expressway Corporation (KEX) Test Road
Geumdang Br. (PSCB) Yeondae Br. (STB)Samseung Br. (SPG)
The Korea Expressway (KEX) test road is a 2-lane one-way expressway built in parallel to Jungbu Inland Expressway in Korea. The total length of the test road is 7.7km, and there are three bridges along the test road. A series of conventional truck loading tests and ambient vibration tests were carried out to prove the proposed SMART Load Rating scheme.
Gamgok IC Yeoju JC
AbutmentAbutment
1 2 3
13121110
987
654
161514
LVDT
No. of accelerometers : 16EASampling Frequency : 200Hz
AccelerometerLDVT
Ambient Vibration Tests
FE Model of Samseung Br
Natural Frequencies and Mode shapes of initial FE model and measured ones (Lower 6 modes)
F1=4.01Hz(4.19)
F2=4.25Hz(4.83)
F3=12.80Hz(11.58)
F4=13.37Hz(12.90)
F5=17.24Hz(14.74)
F6=21.60Hz(18.37)
Modal Parameter ID
1 2 3 4 5 60
5
10
15
20
25
Fre
qu
en
cy (
Hz)
Mode
initial updated measured
Downhill Simplex Method (Nelder and Mead, 1964) was used.
Model Updating
S1 S2 S3 W1 W2 W30.0
0.5
1.0
1.5
2.0
2.5
Load Test AVT
Def. C
orrectio
n F
acto
r
Test Set
Kδ by the SMART Load Rating is
• in a reasonable range compared with Kδ by the conventional method
• more consistent in seasonal varia-tion (summer and winter)
Comparison of Deflection Correction Factors (Kδ)
Proof Test 1 : Samseung Br.
No. of accelerometers : 16EASampling Frequency : 200Hz
AccelerometerLDVT
Ambient Vibration Tests
Proof Test 2 : Geumdang Br.
Natural Frequencies and Mode shapes of initial FE model and measured ones (Lower 4 modes)
Modal Parameter ID
Downhill Simplex Method(Nelder and Mead, 1964)
Model Updating
Comparison of Deflection Correction Factors (Kδ)
Test Vehic le
Test Bridge
Adjacent Bridge
Test Vehic le
Test Bridge
Adjacent Bridge
1 1312111098765432
161514
Gamgok IC Yeoju JC
Pier
Abutment
Pier Pier
LVDT
F1=2.89Hz (2.99) F2=4.02Hz(4.47)
F3=4.69Hz(5.03) F4=7.61Hz(7.51)
1 2 3 4 5 60
2
4
6
8
10
Fre
qu
en
cy (
Hz)
Mode
initial updated measured
S1 S2 S3 S4 S5 W1 W2 W30.0
0.5
1.0
1.5
2.0
2.5
Load Test AVT
De
f. C
orr
ectio
n F
acto
r
Test Set
Geumdang Kδ
Conventional 1.11
SMART-LR 1.18
Palgok III Br.(1996) STB L=230m (40+3@50+40)
Dundae IV Br.(1996) STB L=310m (45+4@55+45)
Gahwacheon (1992) PSCB L=290m (60+120+60+50)
Yeondong Br.(1996) PSCB L=170m (35+50+50+35)
Measurement system installed at the inside of the steel box girder
Ambient Vibration TestsInside of the steel box girder
Sensor Installation along the sideway
Sensor Installation inside the box
Applications to Highway Bridges
FE model using Commer-cial S/W (SAP2k or MI-DAS)
Selection of updating variables
Ambient vib. tests Using smart sensors
Automated Modal Parameter ID
Model updat-ing
SMARTLoad Rating
Integrated GUI
Integrated GUI-based SMART Load Rating System
Integrated GUI-based SMART Load Rating
Field Test on NJ Bridge SB-Span2
Frame 1448
Shell 1401
FE Model
Field Test on NJ Bridge SB-Span2
Test Equipments
Accelerometer
( Model 393B12
(PCB) )
Product Type: Accelerometer, Vibration Sensor
Seismic, high sensitivity, ceramic shear ICP® accel., 10
V/g, 0.15 to 1k Hz, 2-pin top conn.
http://www.pcb.com/spec_sheet.asp?
model=393B12&item_id=9370
Signal Conditioner
(Model 481A03
(PCB))
Signal Conditioner, Modular Signal Conditioner
16-channel, line-powered, ICP® sensor signal cond.
http://www.pcb.com/spec_sheet.asp?
model=481A&item_id=
DAQ Card
(DAQCard-6036E
(NI))
16-Bit, 200 kS/s E Series Multifunction DAQ for PCMCIA
http://www.pcb.com/spec_sheet.asp?
model=393B12&item_id=9370
MUX
(Terminal Block)
(BNC-2090 (NI))
Rack-Mounted BNC Terminal Block
22 BNC connectors for analog, digital, and timing signals
28 spring terminals for digital/timing signals
http://sine.ni.com/nips/cds/print/p/lang/en/nid/1177
Field Test on NJ Bridge
Test set #1
Test set #2
Vertical Lateral
Field Test on NJ Bridge SB-Span2
Field Test on NJ Bridge SB-Span2
0 5 10 15 2010
-10
10-8
10-6
10-4
Frequency
Am
plitu
de
Test1. Sensor No. 11
0 5 10 15 2010
-10
10-8
10-6
10-4
Frequency
Am
plitu
de
Test1. Sensor No. 9
0 5 10 15 2010
-10
10-8
10-6
10-4
10-2
Frequency
Am
plitu
de
Test1. Sensor No. 6
0 5 10 15 2010
-10
10-8
10-6
10-4
10-2
Frequency
Am
plitu
de
Test1. Sensor No. 1
0 2000 4000 6000 8000 10000-0.2
-0.1
0
0.1
0.2
time
accele
ration
Test1. Sensor No. 11
0 2000 4000 6000 8000 10000-0.4
-0.2
0
0.2
0.4
time
accele
ration
Test1. Sensor No. 9
0 2000 4000 6000 8000 10000-0.4
-0.2
0
0.2
0.4
time
accele
ration
Test1. Sensor No. 6
0 2000 4000 6000 8000 10000-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
time
accele
ration
Test1. Sensor No. 1
Field Test on NJ Bridge SB-Span2
0 5 10 150
20
40
60
80
100Stabilization Chart
`
0 5 10 1510
-6
10-4
10-2
100
Frequency (Hz)
Sin
gula
r V
alu
e
Result for Singluar Value Decomposition
0 5 10 150
20
40
60
80
100Stabilization Chart
0 5 10 1510
-4
10-3
10-2
10-1
Frequency (Hz)
Sin
gula
r V
alu
e
Result for Singluar Value Decomposition
Test set #1 Test set #2
Field Test on NJ Bridge SB-Span2
1 - 2 - 3 4 5 6
FEA (initial) 2.615 X 3.70 X 6.15 10.59 7.66 12.13
Test 1
SSI 2.705 3.176 3.383 4.365 5.144 7.851 8.986 11.423
FDD 2.722 3.137 3.5774.211
5.139 7.825 8.972 11.426
Test 2SSI 2.767 3.14 3.321 4.353 5.165 7,647 8.856 11.41
6
FDD 2.734 3.113 3.54 X 5.114 7.703 8.862 11.377
Natural Frequencies [Hz]
Avg. 2.72 X 3.55 X 5.14 7.75 8.92 (11.4)
frequency : f=2.7049 Hz
frequency : f=5.1436 Hz
frequency : f=3.386 Hz
frequency : f=2.7674 Hz
frequency : f=3.3209 Hz
frequency : f=5.1561 Hz
Mode FE Model Test 1 Test 2
1
2
3
Field Test on NJ Bridge SB-Span2
2.615
3.70
6.15
2.72
3.55
5.14
Comparison of identified modal properties
Mode FE Model Test 1 Test 2
4
5
6
frequency : f=11.423 Hz
frequency : f=8.9864 Hz
frequency : f=7.8439 Hz
frequency : f=11.415 Hz
frequency : f=7.6468 Hz
frequency : f=7.6468 Hz
Field Test on NJ Bridge SB-Span2
10.59
7.66
12.13
7.75
8.92
11.4
Comparison of identified modal properties
Field Test on NJ Bridge SB-Span2
Slab
Initial model
Decrease
10% 30% 50%
1 2.615 2.59 2.53 2.46
2 3.699 3.64 3.52 3.36
3 6.15 6.09 5.96 5.79
5 7.662 7.61 7.49 7.31
4 10.59 10.47 10.21 9.91
6 11.12 11.03 10.82 10.51
Cross beam
Initial model
Decrease
10% 30% 50%
1 2.615 2.610 2.596 2.576
2 3.699 3.691 3.670 3.642
3 6.15 6.038 5.794 5.531
5 7.662 7.602 7.326 6.641
4 10.59 10.291 9.641 8.923
6 11.12 11.100 11.041 10.960
Girder - web
Initial model
Decrease
10% 30% 50%
1 2.615 2.594 2.543 2.473
2 3.699 3.668 3.589 3.475
3 6.15 6.106 5.988 5.824
5 7.662 7.570 7.337 6.997
4 10.59 10.536 10.327 10.067
6 11.12 10.972 10.588 10.373
Spring at support (longitudinal dir.) ( ton – m )
Initial model
Increase
10000 5000010000
0
1 2.615 2.843 3.106 3.213
2 3.699 3.971 4.386 4.577
3 6.15 6.188 6.249 6.284
5 7.662 7.952 8.220 8.316
4 10.59 10.601 10.605 10.611
6 11.12 11.941 12.079 12.087
Sensitivity of Updating Variables
Field Test on NJ Bridge SB-Span2
Initial Measured Updated
2.615 2.72 2.716
3.699 3.52 3.570
6.154 5.14 5.178
10.592 7.75 8.085
7.663 8.92 7.93
11.127 11.14 11.0
Parmeter Initial Updated
Slab Stiffness 1 0.523
Cross Beam Stiffness
1 0.505
Spring at Sup-port(Ux)
1 12147ton/m
Web Stiffness 1 1.19
Design Variables
Field Test on NJ Bridge SB-Span2
Conclusions and Future Works
1. Application of Smart Load Rating Procedures
2. Modal parameter ID of the test bridge
3. Selection of Design Variables in Model Updating
4. Low lateral modes (butterfly modes) of the test bridge bad condition in concrete slab and cross beam require more detail investigations on FE model & test data
5. Verification of the updated FE model Truck loading tests
6. Effects of considered modes / design variables
Field Test on NJ Bridge SB-Span2
2 2.5 3 3.5 410
-6
10-5
10-4
10-3
10-2
10-1
Freq. [Hz]
PS
D o
f Acc
el.
Ch.1
s1s2s3s4
2 2.5 3 3.5 410
-5
10-4
10-3
10-2
10-1
Freq. [Hz]
PS
D o
f Acc
el.
Ch.2
s1s2s3s4
2 2.5 3 3.5 410
-5
10-4
10-3
10-2
10-1
Freq. [Hz]
PS
D o
f Acc
el.
Ch.3
s1s2s3s4
2 2.5 3 3.5 410
-6
10-5
10-4
10-3
10-2
10-1
Freq. [Hz]
PS
D o
f Acc
el.
Ch.4
s1s2s3s4
Variation of Natural frequencies
Field Test on NJ Bridge SB-Span2
2 4 6 8 10 12 1410
-6
10-5
10-4
10-3
10-2
10-1
Freq. [Hz]
PS
D o
f Acc
el.
Vertical vs Lateral
Vertical - Ch.2Vertical - Ch.3Lateral at Ch.2
Lateral Motion
Field Test on NJ Bridge SB-Span2
0 0.5 1 1.5-4
-2
0
2
4
6
8
10
Time (sec)
Ou
tpu
t (V
)
271.5 272 272.5 273 273.5 274-3
-2
-1
0
1
2
3
Time (sec)
Ou
tpu
t (V
)
0 50 100 150 200 250 300-5
0
5
10
Time (sec)
Ou
tpu
t (V
)
DAQ System Check-up : Inner Clock
Field Test on NJ Bridge SB-Span2
1 - 2 - 3 4 5 6
FEA (initial) 2.615 X 3.70 X 6.15 10.59 7.66 12.13
Test 1
SSI 2.705 3.176 3.383 4.365 5.144 7.851 8.986 11.423
FDD 2.722 3.137 3.5774.211
5.139 7.825 8.972 11.426
Natural Frequencies [Hz]
frequency : f=3.1756 Hz
frequency : f=4.3651 Hz