Assessing damage evolution in corroded reinforced … · Acoustic Emission Group Project...

Acoustic Emission

Group Project Coordinator

E. Proverbio, University of Messina (IT)

Contributions

Jean P. Balayssac - LMDC, INSA-UPS TOULOUSE (FR)Laurent Gaillet - LCPC NANTES (FR)

Leszek Golaski - Kielce University of Technology (PL)Nora Vilchinska and Energolaboratory Riga (LV)

COST 534 Final Workshop - Toulouse 26-28 Nov. 2007

What is Acoustic Emission?

• Acoustic Emission (AE) is the class of phenomena whereby an elastic wave, in the range of ultrasound usually between 20 KHz and 1 MHz, is generated by the rapid release of energy from a source within a material.

• The elastic wave propagates through the solid to the surface, where it can be recorded by one or more sensors.

• The sensor is a transducer that converts the mechanical wave into an electrical signal.


• Volume inspection• Localization of deteriorated zones• Real time data evaluation

but…• It is possible to detect only damages that are

developing (active defects)

The advantages of AE technique as a NDT method are:


AE parameters

Tinkey B.V., Fowler T.J., and Klinger R.E., (2002) “Nondestructive testing of prestressed bridge girders with distributed damage” research report n° FHWA/TX-03/1857-2


AE signal (reinforced concrete)

Source

High frequency

Low frequency

Medium frequency

High energy

Low energy

Steel wire breakingStress corrosion cracking

Steel corrosion

High energy

Low energy

Concrete cracking

Steel/concrete interface

damaging

Changes in non linear acoustic behavior

of concrete

Structuredamaging

under loading


Source

Rate processanalysis

Global indexes

Moment tensoranalysis

Extrapolation fromsmall sample

Type of crack

Intensity analysis

AE data analysis

Parametric analysis Codification

Calm ratio

Energy analysis


How to manage AE signal

Modelelements

testing

Conventional AE parameters

analysis

Waveform analysis

Sourceidentification

Full scaleelements

testing

Full scalestructuretesting

Sourcelocation

Evaluation of structural integrity


Application examples


Parametric analysis

Hydrogen embrittlement testJean P. Balayssac - LMDC, INSA-UPS TOULOUSE (FR)

●Mechanical behaviour of full scale prestressed concrete girder

Leszek Golaski - Kielce University of Technology (PL) ● Monitoring of a bridge during service

Leszek Golaski - Kielce University of Technology (PL)


Hydrogen embrittlement test

1,00E+02

1,00E+03

1,00E+04

1,00E+05

1,00E+06

1,00E+07

1,00E+08

1,00E+09

0 100000 200000 300000 400000 500000 600000

Time (s)

Ab

solu

te e

ner

gy

(J)

0

10000

20000

30000

40000

50000

60000

70000

Cu

mu

lati

ve c

ou

nts

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6


Group 3 Group 2 Group 1Group 3 Group 2 Group 1

Third group Second group First groupAmplitude (dB) 95-100 40-82 35-50Average frequency (kHz) 40-90 50-150 0-500Energy (J) 108 105-10 7 100-500Duration (µs) 37020 1013 130

Fracture Crackpropagation

Crack initiation


Mechanical behaviour of full scale prestressed concrete girder Leszek Golaski - Kielce University of Technology (PL)

Supervised Pattern Recognition used.

A 26.5-m long and 1-m high prestressed concrete girder was loaded in 4-point bending.


Severity code and description Extent code and description

Code Description Code Description

1 As new condition or defect has no significant effect on theelement (visually or functionally)

A No significant defect

2 Early signs of deterioration, minor defect/damage, no reductionin functionality of element

B Slight, not more than 5% ofsurface area/length/number

3 Moderate defect/damage, some loss of functionality could beexpected

C Moderate, 5%-20% of surfacearea/length/number

4 Severe defect/damage, significant loss of functionality and/orelement is close to failure/collapse

D Wide, 20%-50% of surfacearea/length/number

5 The element is non-functional/failed E Extensive, more than 50% ofsurface area/length/number


Monitoring of a bridge during service

Severely deteriorated three spans bridge

Loaded with heavy traffic lorries


Severity code and description Extent code and description

Code Description Code Description

1 As new condition or defect has no significant effect on theelement (visually or functionally)

A No significant defect

2 Early signs of deterioration, minor defect/damage, noreduction in functionality of element

B Slight, not more than 5% ofsurface area/length/number

3 Moderate defect/damage, some loss of functionality could beexpected

C Moderate, 5%-20% of surfacearea/length/number

4 Severe defect/damage, significant loss of functionality and/orelement is close to failure/collapse

D Wide, 20%-50% of surfacearea/length/number

5 The element is non-functional/failed E Extensive, more than 50% ofsurface area/length/number


Bridge monitoring and failure behaviour of a severely corroded post tensioned girder

Laurent Gaillet - LCPC NANTES (FR)


Merleback bridge


Monitoring system


Acoustic Emission monitoring during service

0

20

40

60

80

100

avr-02

mai-0

2

juin

-02

juil-

02

sept

-02

oct-0

2

nov-

02

janv

-03

mar

s-03

avr-0

3

mai-0

3

juin

-03

juil-

03

Am

pli

tud

e (

g)

Evènements acoustiques détectés pendant la survellance de la poutre 5 rive côté sud surveillance


AE monitoring during bending test


Data analysis “b value”

b-value = 0,3818

b-value = 0,3989

b-value = 0,6048

b-value = 0,613

0

0,5

1

1,5

2

2,5

3

3,5

4

4,5

50-60 60-70 70-80 80-90 90-100

Amplitude range (dB)

log

(n

um

be

r o

f ev

en

ts)

80 to 90 t80 to 85 t70 to 75 t40 to 45 tLinéaire (70 to 75 t)Linéaire (80 to 85 t)Linéaire (80 to 90 t)

loading


Energy analysis

AE monitoring during proof loading of old post-tensioned pre cast segmental viaducts

E. Proverbio, University of Messina (IT)


The viaduct

Type: segmental cast-in-place post-tensioned prestressed concrete box girder

Age: 50 yearsLocation: near seaside


Proof loading


Load steps

II° 50 tonsI° 30 tons

IV° 80 tons

III° 60 tons

V° 110 tons


AE monitoring Sensors: Broadband type (23-80 kHz

bandwidth, 140 pF capacitance)

Threshold: 15 dB

Gain: 34 dB


Main results 1(load step 2)


Main results 2(load step 2)


Main results 3Relaxation ratio analysis – all loads


Nonlinear analysis

Continuous wave AE monitoring of a dam subjected to foundation slow motion

Nora Vilchinska and Energolaboratory Riga (LV)


Advantages

Nonlinear behavior is observed early on in a degradation process, long before linear parameters start to show damage dependent effects.

Any increase in the values of nonlinear parameters is univocally related to an increase in micro-structural features in the material considered.


Cros section of the dam along flow directionby axis of a hydrogenerator.

MPG

70 m

100 m

Water owerflow gates

Hydrogenerator


Response spectra in MP V8 development from 15-Apr-03 till27 27-Apr-05


V18 till and after floods 2004 Analyze in details two silences /High pressure drop down as results of strong oscillations. Q-factor is changed


Conclusions for practice 1 AE techniques can be easily applied as health monitoring

techniques in prestressed concrete since distributed damage causes consistent changes in the acoustic emission response.

The use of “global index” as well as Historic Index, Calm Ratio and Felicity Ratio allow a good quantification of the distributed damage in such structures.

Acoustic emission has several advantages over other NDTs. The main advantage is that it is global. One test can evaluate an entire structure quickly and effectively by placing sensors over the entire structure and stressing it sufficiently. Another advantage is that acoustic emission lends itself well to in-place monitoring. If background noise can be eliminated it may be possible to leave sensors on a bridge, continuously monitor normal traffic, and determine the increase in distributed damage.


Conclusions for practice 2

Acoustic emission also has some drawbacks. One of the most significant drawbacks is that its application is specific, i.e. the interpretation of data require a specific reference database (e.g. reinforced concrete structure, steel structures, prestressed concrete structures, massive concrete structure, and so on). Another drawback is the high attenuation of acoustic emission in concrete. Although low-frequency sensors minimize this effect, it is still significant.

At least, a high qualified personnel is required for in situ application and interpretation.

Assessing damage evolution in corroded reinforced … · Acoustic Emission Group Project...

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