Overview of FHWA Research on NDE Techniques for Cable-stayed and Post-tensioned Bridge ...sp.bridges.transportation.org/Documents/2010 SCOBS... · 2010-06-14 · TURNER-FAIRBANK HIGHWAY

TURNER-FAIRBANK HIGHWAY RESEARCH CENTERTURNER-FAIRBANK HIGHWAY RESEARCH CENTER

Overview of FHWA Research on NDE Techniques for Cable-stayed and

Post-tensioned Bridge Tendons

Seung-Kyoung Lee Manager of Coatings and Corrosion Laboratory

Turner-Fairbank Highway Research Center Federal Highway Administration

May 24, 2010 (AASHTO T-9)

Overview of FHWA Research onOverview of FHWA Research on NDE Techniques for CableNDE Techniques for Cable--stayed and stayed and

PostPost--tensioned Bridge Tendonstensioned Bridge Tendons

Seung-Kyoung Lee Manager of Coatings and Corrosion Laboratory

Turner-Fairbank Highway Research Center Federal Highway Administration

May 24, 2010 (AASHTO T-9)


Presentation OutlinePresentation Outline

• Research Background

• Laboratory Evaluation

• Field Trial of Magnetic Main Flux Method (MMFM)

at the Varina-Enon Bridge, VA

• Planned Field Trial of MMFM at the Luling Bridge, LA


Research BackgroundResearch Background


Corrosion of Post-Tensioned TendonsCorrosion of Post-Tensioned Tendons

After 16 Years, Niles Channel Bridge, Keys, FL (1999)



Niles Channel Bridge, Keys, FL



After 13 Years, Sunshine Skyway Bridge, Tampa, FL (2000)


Sunshine Skyway Bridge, Tampa, FL


After 6 years, Mid-Bay Bridge, Destin, FL (2000)

Corrosion of Post-Tensioned Tendons


Mid-Bay Bridge, Destin, FL


Corroded Post-Tensioned Tendons

Corroded Post-Tensioned Tendons

After 17 years, Varina-Enon Bridge, Richmond, VA (2007)


Laboratory Evaluation ProgramLaboratory Evaluation Program


Artificial Defects by Saw CutsArtificial Defects by Saw Cuts


Artificial Defects by Impressed CurrentArtificial Defects by Impressed Current


Artificial Defects for Internal PT TendonsArtificial Defects for Internal PT Tendons


Internal PT TendonsInternal PT Tendons


NDE Technologies EvaluatedNDE Technologies Evaluated

• Ultrasonic and Sonic Echo/Impulse Response (SE/IR)

• Magnetostrictive Sensor (MsS) Technology for Guided Long-Range Waves

• Microwave Thermoreflectometry

• Remnant Magnetic System

• Magnetic Main Flux Method (MMFM)


Lab TestsLab Tests

[Ultrasonic]

[Sonic Echo/Impulse Response]

Permanent magnets

MsS ribbon coils

[Magnetostrictive Sensor Guided-Wave]

[Remnant Magnetic]


FindingsFindings

• None of the NDE systems was able to detect artificial defects

in the internal PT tendons.

• Presence of grout in the external PT tendons made

propagating signals attenuate significantly and resulted in

most NDE technologies ineffective.


Magnetic Main Flux Method (MMFM)Magnetic Main Flux Method (MMFM)

Carlton Lab at Columbia University


MMFM PrincipleMMFM Principle

N Pole S Pole

Area S

Flux φ

Area S’

Flux φ’

Normal Section

Corroded Section

Magnetic Flow磁束

全磁束検出波形

損傷部モデル

損傷部と検出波形サーチコイルSearch Coil

Damage Model

Detecting Wave

Flux

* The absolute value of metallic area can be evaluated by * The absolute value of metallic area can be evaluated by measuring the parameter measuring the parameter ΔΔØØ..


MMFM System ComponentsMMFM System Components

Wire/StrandWire/StrandSearch CoilSearch Coil

Hall Effect Hall Effect SensorSensor

Constant DC

P.C.P.C.

Gauss Meter

Electrical Cable Electrical Cable

MagnetizerMagnetizer

Flux Meter Data

Recorder

PolaritySwitch


MMFM on PT Tendons – 1st GenerationMMFM on PT Tendons – 1st Generation


Magnetic Flux Chart of Specimen AMagnetic Flux Chart of Specimen A

Estimation of Section Loss (%) 0.2 2.0 0.2


Autopsy Result of Specimen AAutopsy Result of Specimen A

Estimation (%) 99.8 98.0 99.8Actual (%) 99.8 87.6

(16.5 wires) 99.8


MMFM on PT Tendons – 2nd GenerationMMFM on PT Tendons – 2nd Generation


Test Results – Linear RegressionTest Results – Linear Regressiony = 0.999x - 0.1935

R2 = 0.9918

88

89

90

91

92

93

94

95

96

97

98

99

100

88 89 90 91 92 93 94 95 96 97 98 99 100

Remaining Cross- sectional Area (%)

Rate

of

Mag

netic

Flu

x (%

)


Findings - MMFMFindings - MMFM

• MMFM was determined to be the most accurate NDE

system in the lab study.

• Great potential for detecting insidious corrosion in the

external PT tendons, stay cables, and suspension cables.

• It was decided to verify the MMFM technology through field

trials on two bridges with known problems.


MMFM Field Trial at Varina-Enon Bridge, VA (April 27 – May 1, 2010)

MMFM Field Trial at Varina-Enon Bridge, VA (April 27 – May 1, 2010)


Preparation & Getting to the Test AreasPreparation & Getting to the Test Areas


Preparation & Getting to the Test AreasPreparation & Getting to the Test Areas


Test AreaTest Area


Magnetizer SetupMagnetizer Setup


Dummy Wire AttachmentDummy Wire Attachment

¼ in. wire


MMFM TestingMMFM Testing

[Scan Measurement] [Point Measurement]


Raw MMFM Data (Screen Shots)Raw MMFM Data (Screen Shots)

[Scan Measurement] [Point Measurement]


Distance Measurement Distance Measurement


Magnetizer RemovalMagnetizer Removal


AutopsyAutopsy


Temporary RepairsTemporary Repairs


P14S13TE-3

0.2% section loss estimated

by MMFM

Very minor corrosion possible

by MMFM


P14S13TE-3

Autopsy-1

Autopsy-3

[Autopsy-1]

[Autopsy-3]

P14S13TE-3


Autopsy Results (P14S13TE-3, Autopsy-1)Autopsy Results (P14S13TE-3, Autopsy-1)

1,000 mm(39.4 in.)

(No corrosion observed)

(No corrosion observed)

(Minor corrosion observed)

(Minor corrosion observed)

Wall

Wall

Wall

Wall[Wall]


Autopsy Result (P14S13TE-3, Autopsy-3)Autopsy Result (P14S13TE-3, Autopsy-3)

Strands embedded in good condition grout and no corrosion observed [a small nick was found on a wire that was probably created during the excavation work]


P14S13TE-1

No corrosiondamage detected by MMFM


P14S13TE-1

Autopsy-2

P14S13TE-1

[Autopsy-2]

No excavation was made because of a low possibility of discovering corrosion problem.


P14S13TE-2



P14S13TE-2

P14S13TE-2

No excavation


P12S11TE-2



P12S11TE-2

P12S11TE-2Autopsy-4

[Autopsy-4]

Strands were fully embedded in grout and no excavation was made.


P12S12TW-3


by MMFM(1 wire broken)


By MMFM


P12S12TW-3 (Uncovered Condition)


Autopsy Results (P12S12TW-3, Autopsy-5)Autopsy Results (P12S12TW-3, Autopsy-5)

~810 mm (32 in.) from wall ~1,900 mm (75 in.) from wall

2,110 mm (83 in.) from wall

[Wall]

[Partial section loss observed on

several wires]

[Partial section loss observed on

several wires]

[1 wire brokenand heavy

section lossobserved

on several wires]


Preliminary FindingsPreliminary Findings

• It was observed that MMFM was able to identify intact areas

and locations having corrosion damage that ranged from

approximately 0.2 % to more than 0.75 % section loss.

• This finding is consistent with the lab results in that the same

lowest detection resolution (0.2 %) was verified during this

field trial.


Preliminary Findings - ContinuedPreliminary Findings - Continued• However, it could not measure section loss accurately when

a wire was corroded in two (not critical, same issue observed in the lab testing).

• Also, there are discrepancies of up to 20 in. between actual

location of a corrosion damage and where MMFM data

suggested. It might be due to errors in distance

measurements. It needs further investigations.


Preliminary Findings - ContinuedPreliminary Findings - Continued• The current MMFM system demonstrated promising results

of being a fully operable field NDE technology.• A more efficient field MMFM system needs to be improved at

least in the following areas: – Improved cable winding and unwinding methods for the magnetizer – Precise measurement of magnetizer’s travelling distance,– Magnetizer’s better riding ability on the tendons– Self-propelled magnetizer (?)


MMFM Field Trial at Luling Bridge, LAMMFM Field Trial at Luling Bridge, LA


Luling Bridge (Hale Boggs Memorial Bridge)Luling Bridge (Hale Boggs Memorial Bridge)

• Opened in 1983

• Weathering steel

• 1st

cable-stayed over Miss. river

• 2,745 ft. long (1,222 ft. main span)

• 39 out of 72 cables were rated critical


Planned Field TestingPlanned Field Testing

Scan length/cable = ~20 ft.

Magnetizer

Electrical winch

• No. of cables to be inspected = 3-5• No. of autopsy samples = three 10-ft. sections• Removed samples will be transported to FHWA Corrosion Lab for detailed autopsy


Thank you!Any Questions?