advanced strategies and recent results on health ... · field test 24 "healthy" bridges...

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


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


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

��

(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

��

��

KEY

From Page 166of Bridge Plans

STAY CABLE CONTAINMENT INSTRUMENTATION

Geokon Model VCE-4200

(16) Geokon Vibrating Wiresampled every 15 minutes

��

STRAIN GAGE PAIR PVC CONDUIT DATA SYSTEM

��

��

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


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

��

STRAIN GAGE PAIRS: Steel Foil and VWG Concrete Foil and VWG

ACCELEROMETER PVC CONDUIT DATA SYSTEM

KEY

��

��

Close-up Sectional View ofCIP Joint over Fascia Girder

Not Shown: Longitudinal PVC Conduit in Exterior Traffic BarrierFrom Page 106of 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

advanced strategies and recent results on health ... · field test 24 "healthy" bridges...

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