advanced strategies and recent results on health ... · field test 24 "healthy" bridges...
TRANSCRIPT
Profs: Arthur Helmicki, Victor Hunt, James Swanson, Douglas Nims
Students: Xiaoyi Wang, Scott J. Kangas, DivyachapanPadur, Lei Lui, Balram Chamaria
Advanced Strategies and Recent Results on Health Monitoring and Condition Assessment of Bridges
UCII Ohio bridge field test program24 "Healthy" Steel Stinger Bridges
16 Tested to Date10 "Low Rated" Steel Stringer Bridges
8 Tested to Date
District 8:HAM-27(x2), HAM-126(x3), CLE-52(x3), BUT-732, PRE-725, PRE-503, CLI-132
District 7:AUG-75, MOT-70(x2), MOT-75
District 12:LAK-90(x2), CUY-77(x2)
District 3:RIC-30(x3)
District 10:ATH-356
District 5:LIC-184, FAI-33
District 11:TUS-212, TUS-751
District 6:MAD-70(x2), MAD-40
RIC-30-1384 7001320 3RIC-30-1438 7001479 3RIC-30-1638 7001517 3FAI-33-7.31 2301067 5MAD-70-1555L 4902858 6MAD-70-1555R 4902882 6MOT-70-2210 5706270 7MOT-75-0776 5706939 7HAM-126-1279 3104850 8HAM-126-1317 3105172 8TUS-212-1509 7904533 11TUS-751-0420 7906307 11CUY-77-0645L 1806181 12CUY-77-0645R 1806211 12LAK-90-1641L 4304624 12LAK-90-1641R 4304659 12BUT-732-1043 903841 8PRE-725-0880 6804209 8CLE-52-0498L 1301535 8CLE-52-0498R 1301594 8HAM-27-1550L 3101746 8HAM-27-1550R 3101770 8
LIC-158-0164 4505379 5MAD-40-0745 4901290 6MOT-70-0553 5704952 7AUG-75-0201 601926 7CLE-52-0142 1301357 8CLI-132-0083 1402587 8PRE-503-1170 6803660 8ATH-356-0459 504203 102 More to Test
8 More to Test
24 Bridge Project
Low Rated Bridge Project
Project Goals and TasksDevelop database of experimental results for more diverse population of steel-stringer bridges
Field Test 24 "Healthy" Bridges
Field Test 10 "Low Rated" Bridges
Demonstrate practicality and usefulness of field test tools
Streamline On-site Test CapabilitiesModal Impact Test (Global Information)Crawl Speed Truck-load Test (Local Information)
Develop Software ToolsEfficient FE model generationEfficient calibration techniques
Efficient rating calculations
Investigate Bridge Condition on Statistical Basis
Analytical vs. Experimental Flexibility
AF N SB RQPMLKJIH
GEDC
1
OT
U
2
34
5
A B C D E H I J K L M P Q R SF N T U
-0.012-0.011-0.010-0.009-0.008-0.007-0.006-0.005-0.004-0.003-0.002-0.0010.000
Def
lect
ion
(in
.)
Calibrated ModelImpact Test
- non-posted condition- 0.7 - 0.8 span ratio- built after 1950
- # of spans- skew- composite/noncomp.- stub or integral abut.- max. span length- bridge width
- mainline route- ADTT>2500
Field Test 40 (6+24+10) Bridgesx bridges in each family
statistical database for family90% or 95% conf. interval
Str
ess
(ksi
) fro
m T
ruck
Lo
ad
Truckload Response, West Lane Path
Front Axle Location (feet)
NorthPier
SouthPier
SouthAbutment
NorthAbutment
0 20 40 60 80 100 120 140 160 180 200-1.3
1.3
-1
-0.5
0
0.5
1
North Span, Beam 3 Middle Span, Beam 3 South Span, Beam 3South Pier, Beam 3North Span, Beam 4 Middle Span, Beam 4 South Span, Beam 4
Girder 1
Girder 2
Girder 3
Girder 4
Girder 5
BUT-732-1043SN
4 Spaces@ 8'-4.5"= 33'-6"Path
Truck Load
60'-0" 75'-0" 60'-0"
UCII Field-Test-Based Rating Strategy
Bridge Record
Data
TruckloadTest Data
Modal TestData
UCII Post-Processing
Algorithms
UCII Post-Processing
Algorithms
Analytical andEngineering Calculations
RatingCalculations
FE Modeling
Simulation, Rating, Condition Assessment,
Statistics, etc
Analytically-Based Ratings
Field-Test-Based Ratingsand Other Results
Material/SampleTest Data
Capacity, Dead Load, and Live Load
Actual Live Load Stresses and Unit Influence Lines
Flexibility, Mode Shape, and Frequency
Estimates of Capacity,Live Load, and Dead Load
Existing RatingApproach
UCII Field-Test-BasedApproach
Actual Material Strengths, Modulus of Elasticity, and other Properties
ModelCalibration
Nominal FE Model
Bridge Modeler Software
3 Span Bridge:
• 2571 Joints
• 1928 shell elements
• 1633 frame elements
3D FE Model4 Span Bridge:
• 3755 Joints
• 2820 shell elements
• 2125 frame elements
Bridge Modeler
Some Other Bridges:
• More Joints
• More elements
No. of Nodes and Elements
3D FE Modeling Strategy
Cross-Section of Super Structure
Rigid Links
Support Links
Supports
Steel Girders
Abuts/Piers
Concrete Deck
Elevation of Bridge
Strain/Stress Responses - UIL
-0.01
-0.005
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
Stre
ss(k
si)
Span 1 Span 2 Span 3
Stress Response
Unit Axle Load
Velocity
Stress Responses - UIL
Mode Shapes - Mode Types
B-111-OO
T-111-OO
F-111-OO
Identifying Modes of Bridge
Complex Mode Indicator Function (CMIF) assimilates all accel responses into 1 plot Each line represents a unique impact location (6 impact pts = 6 lines)
Frequency, (Hz)0 5 10 15 20 25 30
10 -9
10 -8
10-7
10 -6 Complex Mode Indicator Function Plot
Lo
gM
ag
Drop Hammer Accelerometer
Bridge
-37
-34
-31
-28
-25
-22
-19
-16
-13
0 20 40 60 80 100 120 140 160 180 200
dB
Mag
nit
ud
e (l
bf)
Frequency (Hz)
Time (sec)
-20
0
20
40
60
80
100
-0.029 0.971 1.97 2.97 3.97
Input Signal Output Response
-1.00
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
1.00
-0.06 0.94 1.94 2.94 3.94 4.94 5.94 6.94 7.94
Time (sec)
1.E-03
1.E-02
1.E-01
1.E+00
0 10 20 30 40 50 60
Lo
g M
agn
itu
de
(g/lb
f)
Frequency (Hz)
Modal Order/ Average BGCI Contribution
1st 9 mode shapes have been found to be common to 3-span, 5-girder bridgesThese 9 modes dominate dynamic behavior (providing approx 90% of response)
2
1
0
1
2
3
4
0 25 50 75 100 125 150 175 200
F-111-OO 4.97 Hz
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0 25 50 75 100 125 150 175 200
T-111-OO 5.54 Hz
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 25 50 75 100 125 150 175 200
F-121-OO 7.26 Hz
.5
.4
.3
.2
.1
0
.1
.2
.3
.4
0 25 50 75 100 125 150 175 200
T-121-OO 8.21 Hz
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
00 25 50 75 100 125 150 175 200
F-111-II 8.62 Hz
0
0.1
0.2
0.3
0.4
0.5
0 25 50 75 100 125 150 175 200
T-111-II 9.39 Hz
0 25 50 75 100 125 150 175 200
B-111-OO 11.86 Hz
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 25 50 75 100 125 150 175 200
B-121-OO 14.19 Hz
-0.45
-0.4
-0.35
-0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0 20 40 60 80 100 120 140 160 180 200
B-111-II 14.70 Hz
1 2 3 4 5 6 7 8 9F-111-OO T-111-OO F-121-OO T-121-OO F-111-II T-111-II B-111-OO B-121-OO B-111-II
8.78 2.89 2.41 2.50 45.46 16.71 2.09 1.40 11.74Contribution (%)
Mode #Mode Type
Girder 3Girder 4
F - FlexuralT - TorsionalB - Butterfly
I - In Phase O - Out of Phase
1 - 1 peak in Span2 - 2 Peaks in Span
2
Truckload Testing
Data acquisition system Moving load – weighed dump truck Strain gage
• Truckload test measures the static response of a bridge
• Local behavior of a bridge can be identified
• The stress response obtained from the tests is used for bridge rating
• A loaded dump truck with known axle weights is run at crawl speed, instead of static test
• Truck runs are conducted on all the lanes of the bridge
• Truckload tests are conducted with minimum disturbance to the traffic
2
Calibration Diagram
-0. 4
-0. 2
0
0. 2
0. 4
0 50 100 150 200 250
M ode #3 (6. 0536 Hz , 2. 2014
zet a)
Test data: Modal + Truckload
Nominal modelCalibration program
Calibrated model
Before calibration During calibration After calibration
4
Advantages of Automatic Calibration
• Hours: The weeks’ work of calibration is shortened to within 48 hours.
• Parameters: More FE parameters are calibrated, provide a better data-fit to the reality.
0
100
200
300
400
500
600
manual calibration computer calibration
Auto-Calibration Advantages
hoursparameters
6
Objective FunctionUILUILFreqFreqMACMACBGCIBGCI OFwOFwOFwOFwGOF ⋅+⋅+⋅+⋅=
Calibration Process Diagram
0
0.05
0.1
0.15
0.2
0.25
0.3
0 100 200 300 400
Calibration Ite rations
Obj
ectiv
e Fu
nctio
ns' V
alue
s
Global OFBGCI OFMAC OFFrequency OFUIL OF
Calibration is started from nominal model Calibration is done, Tuned Model
7
Calibration Parameters
• All the parameters are set with limitation to have realistic values.
10-6 ~ 1061Moment of Inertia of Rigid Links (IRL), in4
27000~3100029000Modulus of Elasticity of Steel (ES), ksi
6~11From planThickness of Deck (TD), in
2000~60004750Modulus of Elasticity of Concrete (EC), ksi
10-4 ~ 1051Moment of Inertia of Support Links (ISL), in4
10-2 ~ 1053000Area of Support Links (ASL), in2
Calibration Limitation
Nominal ValueParameters
Flexible Support
Composite Action
IRL
EC,TD
ASL,ISLES
General Information of Parameters and Bridges
Parameter Summary Parameter Value
Parameter Name
Nominal Value
Calibration Limitations
Area of Support Links (ASL), in2 3000 10-2 – 105 Moment of Inertia of Support Links (ISL), in4 1 10-4 – 105 Modulus of Elasticity of Concrete (EC), ksi 4750 2000 – 6000 Thickness of Concrete Deck (TD), in From bridge plan 6 – 11 Modulus of Elasticity of Steel (ES), ksi 29000 27000 – 31000 Moment of Inertia of Rigid Links (IRL), in4 1 10-6 – 106
Bridge IntroductionBridge Overall
Length (ft.) Year Built
No. of Supports
No. of Girders
Skew Angle (Deg.)
Deck Thickness (in.)
BUT-732-1043 195 1952 4 5 0 8.5 PRE-725-0800 192 1968 4 5 -10 7.75 HAM-27-1550L 175.5 1970 4 5 -9 9 HAM-27-1550R 195 1970 4 5 -9 9 CLE-52-0498L 221 1965 4 6 0 8.75 CLE-52-0498R 221 1965 4 6 0 8.75 RIC-30-1438 221.5 1971 5 6 0 8.5
Areas of Support Links-Vertical Stiffness
Support Links(Elevation) Bearing Conditions
0.001
0.01
0.1
1
10
100
1000
10000
100000
1000000
BUT PRE HAM-L HAM-R CLE-L CLE-R RIC
Bridge
Are
a (in
^2)
Cal Support1 Cal Support2 Cal Support3 Cal Support4Cal Support5 Nom Max Min
Distribution of Areas of Support Links
Modulus of Elasticity of Concrete
Concrete Stripes (Plan) Road Surface Conditions
1000
2000
3000
4000
5000
6000
7000
BUT PRE HAM-L HAM-R CLE-L CLE-R RIC
Bridge
Mod
ulus
of E
last
icity
(ksi
.)
Cal Girder1 Cal Girder2 Cal Girder3 Cal Girder4 Cal Girder5Cal Girder6 Nom Max Min
Distribution of Modulus of Elasticity of Concrete
Moment of Inertia of Rigid Links-Composite Action
Steel Girders (Elevation) Composite Action Levels
0.0000001
0.00001
0.001
0.1
10
1000
100000
10000000
BUT PRE HAM-L HAM-R CLE-L CLE-R RIC
Bridge
Mom
ent o
f Ine
rtia
(in^
4)
Cal Girder1 Cal Girder2 Cal Girder3 Cal Girder4 Cal Girder5Cal Girder6 Nom Max Min
Distribution of Moment of Inertia of Rigid Links
Bridge Rating Statistics
BARS, Trucktest, FE Model Load Rating Comparison
0
0.5
1
1.5
2
2.5
3
Rat
ing
BARS 1.05 0.95 1.4 1.2
TRUCK TEST 1.63 1.6 2.54 2.56
Nominal Model 1.73 1.65 2.52 2.38
Tuned Model 1.35 1.66 2.64 2.66
BUT 732 PRE 725 CLE 52L HAM 27L
HS20 Truckload Rating
1.52 1.52
1.36
1.73
1.26 1.22 1.16
1.42
1.060.92
0.77 0.82
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0903841 6804209 1301535 3101746
Butler Preble Clermont Hamilton
DF, ASD DF, LRFD DF, UCII
Distribution Factors for Similar Stringer Bridges
Dis
trib
uti
on
Fac
tor,
Wh
eel
Liv
elo
ad,
Tw
o L
anes
1.0
3
2.06.0
125.975.0,
+=
S
g
LtK
LSSLRFDDF
5.5, SASDDF =
BARSMUCIIMASDDFUCIIDF
LL
LL
,,,, ∗=
30.47
39.3443.21
52.35
10.8312 12.25
13
2.24
10.61
14.10
15.66
67 7
8
0
10
20
30
40
50
60
0903841 6804209 1301535 3101746
Butler Preble Clermont Hamilton
0
2
4
6
8
10
12
14
16
18
%Reduction LL Crossframe Spacing (feet) Effective Deck Width (feet) General Appraisal (0-9)
Relationship of Design and Condition Parametersto the Reduction of BARS Liveload
Par
am
eter
Val
ue
, as
giv
en
in t
he
Key
be
low
Re
cuct
ion
of
BA
RS
Liv
elo
ad (
%)
Can we use Inspection to Scale BARS LL?
An Effect of Xframe spacing?
An Effect of Unintended Composite Action?
Where is the increasing difference from BARS LL coming from?
CONCLUSIONS TO DATE
Impact and truck-load testing can be performed practically and efficientlylane-by-lane "rapid" multi-reference impact testinglane-by-lane truck tests
Modal and truck-load tests provide reliable, accurate, useful information on bridge condition
Calibrated 3D FE models can be readily obtained and help establish more realistic load-rating and safe load-carrying capacity
Objective methods meant to complement inspection and load-rating
NOT REPLACENOT REPLACE
View of construction site as of November 12, 2003 (taken from OH side)
Digital rendering of completed structure (viewed from KY)
US Grant Bridge: SCI-23-0000US Grant Bridge: SCI-23-0000
View of construction site as of November 7, 2003 (taken from KY tower)
Potential BenefitsPotential BenefitsFormation of a team with the knowledge and expertise to support ODOT's efforts to effectively manage these structures.
Support inspection effortsProvide hard data for recommendations on actions taken throughout bridge life-cycle: construction and service.
Development of a database of objective field information on these structures.
Translate an understanding of US Grant behavior.Better understanding of maintenance issues.Track USG structural performance.
Deeper understanding of the general behavior and performance of cable stayed bridges in general.
EVENTS LOAD EFFECTS
DEAD LOADS
INTRINSICFORCES
LIVE LOADS
CAPACITY REDUCTION
CONSTRUCTION
ERECTION
FABRICATION
ACCIDENT
FLOOD
DETERIORATION
EARTHQUAKE
SEASONAL SOIL CONDITION
ENVIRONMENTAL CHANGES
LONG-TERM CLIMATE
AMBIENT CONDITION CHANGES
TRAFFIC
HYDROLOGICAL
Safety?Serviceability?
Weather Station
CR-10 Network
VW Gages
Thermistors
Low Speed/Environmental Monitor
Traffic Monitor
OPTIM
Resistive Gages
Accelerometers
Main cabinet w/PC
Research Labs/ODOT
Web/Phone/Modem Remote Connection
Vibration Monitor
Overall Monitor ArchitectureOverall Monitor Architecture
Criterion Stay CableWORST RATING 1S, 1NMAX LOAD FORCE 1S, 1NMAX DEAD STRESS 8N
SUMMARY PLAN FOR INSTRUMENTATION OF STAY CABLES 1, 8, & 16
4B 16A16B
INSTRUMENTED SECTIONCOAXIAL and OTHER CABLEMAIN COMPUTER CABINETCSAT3 WIND SENSOR
������������
NEMA Cabinet, 2 x 3 x 6 feet with 120VAC, 15A power, analog phone, and air ventsComputer with modem
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(1) Campbell Scientific:CSAT3 Wind SensorCR10X-2M dataloggerMD9 MultidropENC 16/18 EnclosurePS12LA Power Supply
CSAT3 Wind Sensor
Optim Electronics:continuous 200 samples per secondstores data crossing pre-set thresholds(1) 3415 MEGADAC system(8) AD808, 8-channel cards
Campbell Scientific:(1) CR10X-2M datalogger(1) MD9 Multidrop(1) ENC 16/18 Enclosure(1) AVW1 Interface
1N16N16S1S
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KEY
From Page 166of Bridge Plans
STAY CABLE CONTAINMENT INSTRUMENTATION
Geokon Model VCE-4200
(16) Geokon Vibrating Wiresampled every 15 minutes
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STRAIN GAGE PAIR PVC CONDUIT DATA SYSTEM
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Strain gage pairs installed with steel clamp to the rebar cage of the concrete
containment.
Strain gage cables routed through rebar cage to the data system cabinet.
Data system cabinet is embedded within or attached upon the pylon wall.
Strain gage pairs installed in a T or cross pattern in order to
measure radial and longitudinal strains and deformations in the
containment immediately adjacent to the cradle sheath
for the stay cable
KEYCampbell Scientific:
(1) AM416 Multiplexer(1) AM ENC Enclosure
Data System
From Page 111of Bridge Plans
Stay Cable Instrumentation:(2) PCB PiezotronicsCapacitive Accelerometers (3701)Note: roved to various
instrumented sections
Concrete Embedment Sensors:(4) MM Resistive Foilsampled during semi-annual testsor connected to Vibration Monitor
Concrete Embedment Sensors:(4) Geokon Vibrating Wiresampled every 15 minutes
SECTION INSTRUMENTATION PLAN (Sectional View)
Geokon Model VCE-4200
Micro Measurements Model EGP-5-120
Steel Tag-Welded Sensors:(8) TM Resistive Foil Strainsampled during semi-annual testsor connected to Vibration Monitor
Steel Epoxied Sensors:(8) Geokon Vibrating Wiresampled every 15 minutes
Geokon Model VSM-4000
Texas Measurements AWC-8B
PCB Model 3701
Campbell Scientific:(1) AM416 Multiplexer(1) AM ENC Enclosure
Optim Electronics:(2) AD808FB/120
Data System
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STRAIN GAGE PAIRS: Steel Foil and VWG Concrete Foil and VWG
ACCELEROMETER PVC CONDUIT DATA SYSTEM
KEY
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Close-up Sectional View ofCIP Joint over Fascia Girder
Not Shown: Longitudinal PVC Conduit in Exterior Traffic BarrierFrom Page 106of Bridge Plans
From Page 162of Bridge Plans
Load Factor Inventory Rating Factors[using HNTB section properties]
0.1
1
10
100
1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000
Station (feet), KY Tower at 1487 feet, OH Tower at 2362 feet
Ptv LL Moment (composite section) Neg LL Moment (noncomposite section)
Potential Sections to be Instrumented
EXAMPLE SENSOR PLAN FOR AMBIENT MONITORING DYNAMIC MODE SHAPES US Grant Bridge Superstructure
PCB Piezotronics Capacitive Accelerometers (3701)
Sensors installed in both the Y and Z coordinates to observe vertical and lateral modes
**MODE 1 FREQ 0.2918 CYC/SEC
EXAMPLE SENSOR PLAN FOR AMBIENT MONITORING DYNAMIC MODE SHAPES US Grant Bridge Superstructure
PCB Piezotronics Capacitive Accelerometers (3701)
Sensors installed in both ? (as high up as possible) the X and Y coordinates to observe longitudinal & lateral modes at stay anchor
**MODE 1 FREQ 1.0 – 3.0 CYC/SEC (not accounting for sag)
mT
Lf
21
=
At approx EL 600'
OH Tower InstrumentationOH Tower Instrumentation
N
Environmental loads
Ere
ctio
n lo
ads
View of tower rebar cage
OH Tower @ EL 600 Moment and Axial Forces During Erection (B&T)
0
2000
4000
6000
8000
10000
12000
14000
160001 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100
103
106
109
112
115
Erection Stage
Axi
al F
orc
e (k
ip)
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
Mo
men
t (1
000
kip
-ft)
P M
Tow
er p
our
Seg
men
t Ere
ctio
n
Temporary bent
Cre
ep, S
hrin
kage
, etc
.
Opening Day
Recent view of construction site
Digital rendering of completed structure
Maumee River CrossingMaumee River Crossing
Instrumented Segment in Storage in Casting Yard
Segment SelectionSegment Span 27-4 Span 27-41 Span 28-3 Span 28-28
In-Service Highpoints
All bottom RFs low, Top temp. RF low, Top LL is close to abs. max., Segment between two longest stays.
Good LL response, Bottom RFs are high. Top RFs are low. Near the center of back-span.
Low RFs. Both 27-67 and 28-3 are near the shortest stays.
RFs are lower than 28-34. Best bottom LL response and Low top RFs.
In-Construction Highpoints
Low max. stress, Not very responsive to construction until phase 210+ (Day 559).
Low max. stress, Responsive to construction after phase 24 (Day350), Responsive to pier removal, Stresses uniform throughout the length.
Good construction response, Uniform stress throughout segment length.
Responsive through the end of construction, Peaks pronounced and good magnitude, Uniform stress.
TYPICAL SEGMENT INSTRUMENTATION LAYOUT
STRA IN G AGE PAI RS: LONG ITU DIN AL LATER ALACCELE ROMETE R
PV C CON DU IT JUN CTIO N BO X
Strain gag e pairs installed in r ebar cage by URT at time o f castingStrain gage cables r outed by URT thr ough r ebar cage to the junction boxes.Junction boxes installed by con tractor within the concrete Je rsey barr ie rs.Con duit with 3" inner diameter installed by contr actor to con nect the junction boxes.
Geoko n Mode l VCE -420 0
Mic ro Me asure ment s Mode l EGP -5-35 0
MM Resistive Foil S tr ain Gage:sampled during semi-annual testsor connected to Vibration Monitor
Geokon Vibr ating Wire S tr ain Gage:sampled every 15 minutes
Campbell Scientific :(1) C R10X-2M datalogger(1) MD 9 Multidrop(1) EN C 16/18 Enclosure(1) PS12LA Power Supply(1) AM416 Multiplexer(1) AVW1 Inter face
Ca mpbe ll S ci ent if i c Mod el CR-10X -2M
Note : The fo ur such sege ments of t he MRC will be instr umented. The a bove diagram is sim ply a repr esentation of the instrum entation plan . All conduit a nd cables to be provided concur rent with section e rection, with installation to t he Jersey bar rier concu rrent with ba rrier con struction and with installation of 1 20VAC power concur rent with othe r bridge electrical wo rk.
VIEWS OF EMBEDMENT GAGE INSTALLATIONS
VIEWS OF INSTRUMENTED SEGMENTS
12 2
1
Instrumentation planOne vibrating wire and one sister bar at each location
Delta frame Storage and vertical lifting position
Delta frame Tensioning tendons layout
Post-tensioning sequenceData Collection
• Stage #1 DF2 tensioned (2pm)
• Stage #2 DF3 tensioned (2:26pm)
• Stage #3 DF1 tensioned (2:42pm)
Strain gage readingsGage readings during the process of tensioning
-80
-60
-40
-20
0
20
40
60
80
100
Time
1100
1115
1130
1145
1200
1215
1230
1245
1300
1315
1330
1345
1400
1415
1430
1445
1500
1515
1530
1545
1600
1615
1630
1645
Time (hrs)
Rea
ding
s (m
icro
stra
ins)
18BVNTO
18BSNTO
18BSNBI
18BVSTO
18BSSTO
18BVSBI
18BSSBI
Prestressing
begins
DF2 tensioned
DF3 tensioned
DF1 tensioned
Modeling in BD2• 2D dimensional stiffness method• Can model post-tensioning losses• Other losses like elastic shortening are also modeled• Good for staged loading• Time dependent properties like shrinkage and creep can also be
modeled, but not considered in this analysis as the process takes place over a span of only one hour.
• Duct properties used as provided by the consultant• Jacking forces and seating loss obtained by PT stressing log• Used for change in strains due to tensioning of tendons
Modeling in BD2
Test-Model CorrelationAssumptions:• Plane section remains plane• Homogeneous materials• No cracks in the bottom chord• Strain gages not dislocated and measurement in the right
direction• No affect in accuracy of gages due to temperature• The gage represents its centerline strains• Linear noise can be separated by simple arithmetic's• Immediate force transfer• No effect of shrinkage, creep and temperature (over a short
period of 1 hr)• No effect of dead load deformations
Comparison: Normalized strains
Comparison: Normalized strains
Great match after ‘normalizing’. Analytical and
experimental results agree well at all three
stages.
Conclusion
• No crack in bottom chord• Very good agreement between analytical
and experimental results• Eccentricity is an issue while using 2D
models• Losses and other design assumptions are
fairly accurate