ACOUSTIC EMISSION (AE) FOR STRUCTURAL HEALTH …

09/11/2017

1

Project co-funded by the EU under H2020

ACOUSTIC EMISSION (AE) FOR STRUCTURAL HEALTH MONITORING

Jon WatsonInfrastructure DirectorMistras UK

Dr. Athanasios AnastasopoulosVice PresidentMistras Group Hellas A.B.E.E.

1st SENSKIN Workshop, 8 Nov. 2017, Brussels

Why Structural Monitoring?

• Health monitoring - performance vs modelling

• Fatigue assessment – stress and load cycles from strain

• Crack detection, location and monitoring

• Cable and post tension wire break detection

• Structural movement especially bridge bearings

• Monitoring during construction – temporary works

• Land slide / Rock fall detection, early warning and monitoring

• Corrosion monitoring

• Impact – bridge strikes

• Weather and earthquake loading Main Benefits• Ensure and Increase safety

• Increase life and availability of structure

• Reduce operating costs


09/11/2017

2

Monitoring Experience and Applications


• Bridges- Aging assets- Strengthening schemes- New build

• Civil nuclear

• Military structures

• Buildings/car parks

• Oil and Gas- Process- Storage (LNG/liquids)

• Offshore structures- O&G- Wind energy

Monitoring and Data Outputs


09/11/2017

3

Monitoring and Data Systems

© Mistras Group 2017 www.mistrasgroup.com

Many different systems to meet the monitoring needs, between £1k - £500k


Monitoring Technologies

• Acoustic Emission

• Displacement or movement

• Rotation

• Strain (resistance or Fibre Optic)

• Vibration / acceleration

• Weather stations (wind, temp, rain etc)

• Dynamic and static measurements

• Weigh in motion

• Total station – remote laser movement monitoring

• Corrosion monitoring

- Local pH

- Local humidity

- LPR corrosion potential

Any Sensor

e-mail1st SENSKIN Workshop, 8 Nov. 2017, Brussels

09/11/2017

4

Sensors, Gauges and Prisms

Many different sensors to get the data you need to manage your structure


© Mistras Group 2017 www.mistrasgroup.com

According to ASTM, the term Acoustic Emission refers to “the class of phenomenawhereby transient elastic waves are generated by the rapid release of energy fromlocalized sources within a material, or the transient waves so generated”.

DEFINITION AND BASIC PRINCIPLES


09/11/2017

5

THE AE SIGNAL


• Basic signal features describing signal shape are calculated, recorded and analyzed in real-time!

• Waveforms themselves can also be recorded.

Real-time evaluation or post processing analysis with graphs and location of AE

Time Driven Data (threshold Independent) usually RMS vs. Hit Driven Data (Threshold Dependent)

Crack initiation

Shock wave detected by sensor

BURST TYPE OF ACOUSTIC EMISSION SOURCES IN STRUCTURAL INTEGRITY APPS


09/11/2017

6

LINEAR LOCATION OF SOURCES

Source Close to sensor 1: Note the difference in arrival times Source in the middle: Time difference equals zero

1 2

Χ

L

ΑΕ SOURCE

Χ=1/2(L-VΔΤ)


LABORATORY EXAMPLE I – NECESSITY of DAMAGE EVALUATION TECHNIQUE


09/11/2017

7

LOADING & CONVENTIONAL APROACH

Displacement-Time

AE ?

• Cracks are not visible until late stage loading ...Not at all in case of repair

• Load Displacement Curve does not permit damage characterization until almost final failure ...

Load–Displacement Load vs. Time


LOADING & AE APROACH

Displacement-Time

AE Energy Release Rate provides Real Time info on damage built up and accumulation at early stage ...

Load–Displacement Load vs. Time


09/11/2017

8

DAMAGE CHARACTERIZATION BY MEANS OF AE

AE parameters evolution vs. time (Load vs. Time Curve Superimposed)

4 DAMAGE STATES:

0-550 sec const. energy (18e6 αJ) and slope & low amplitude.

550-1180 sec energy increases up to 6,7e8 αJ, higher slope & amplitudes

1180-1600 sec energy jump 2,3e9 αJ & amplitude increase

1600 sec to the end max energy 2,6e9 αJ. Different slope


LABORATORY EXAMPLE II

1

6 2

12 5

4

3

7

8

9

10

1114 13

AE sensors position at Front Side .AE sensors position at the back Side of

the beam.


09/11/2017

9

DAMAGE LOCATION AND CHARACTERIZATION

▪ Absence of located events in the center –increased density of located events with orientation of the cracks under development – well correlated with VT

▪ Graph indicating the time vs. x position of damage indicative of damage progression vs. load/time (start at center then at edges)


INDICATIONS AND DAMAGE EVALUATION PRIOR VT & AT EARLY STAGE

STATISTICAL EVENTS DISTRIBUTION INDICATIVE OF SHEAR FAILURE

DAMAGE LOCATION AND CHARACTERIZATION


09/11/2017

10

ΑΕ System AE sensors1st SENSKIN Workshop, 8 Nov. 2017, Brussels

AE SET UP

AE ACTIVITY PER COLUMN DURING COMPLEX DYNAMIC LOADING OF BUILDING

• The majority of the AE activity, around 98%, is emitted from columns 1 and 2 recorded during both positive and negative loadings (during negative only for columns 3 and 4).

• The AE activity starts at certain loading level, due to past loading simulating earthquake of 0.30g.

• The absence of AE activity during the accidental load hold at relative high load levels at time between 5000-5800sec, is worth noting.


09/11/2017

11

Top

Base

Top

Base

C1

C2

C3

C4

DAMAGE EVALUATION & CHARACTERIZATION PER COLUMN DURING COMPLEX DYNAMIC LOADING OF BUILDING

10/11/05 – Post failure assessment

09/11/2017

12

09/11/2017

13

Examples of Wire Break Monitoring of Cables

Ben Franklin Suspension Bridge, USAManhattan Suspension Bridge, NYC, USA

Ben Franklin Suspension Bridge , USA

Humber Suspension Bridge , UK

R&D Project at Columbia University


Steel Structure Monitoring

Steel girder bridge, M4 motorway over River Thames

Lowestoft orthotropic steel deck lifting bridge

Orthotropic deck fatigue monitoring Avonmouth Bridge M5 Motorway

09/11/2017

14

“Semi-global” Monitoring

Steel Box Girder Monitoring

Steel girder bridge, M6 motorway

M8 motorway, Glasgow, Scotland

Steel girder butt weld testing A38(M), Birmingham

Bidston Moss, M53 motorway

Steel girder bridge, A34(M) motorway

White Cart Viaduct, M8 motorway

Gravelly Hill, M6 motorway

Summary Steel Fatigue ResultsM48 Severn Bridge England

Ben Franklin Suspension Bridge, USA

Royal Navy Dock, Scotland

Ben Franklin Suspension Bridge , USA

Severn Suspension Bridge , UK

Active (minor) fatigue like sourceat 10.8m along the girder

Example fatigue location results and results summary

09/11/2017

15

Concrete Structure Monitoring

Concrete bridge, M25 Motorway South England Concrete bridge, A14 Cambridge England

Concrete bridge, M4 Motorway London Concrete bridge, M50 Motorway West England

Summary Concrete Monitoring ResultsM48 Severn Bridge England

Cable Stay Bridge, USA

Active concrete micro fracture


09/11/2017

16

Summary Concrete Monitoring Results


Summary Concrete Monitoring Results


09/11/2017

17

DISCUSSION & CONCLUSIONS

➢ Acoustic Emission can be used for direct assessment of Structural Risk and Reliability for the applied conditions.

➢ Acoustics Emission deliver clear, accurate information from monitoring that helps engineers to - increase structural safety- assess condition of materials and structure- optimise asset management- maximise safe structural life- minimise whole life costs

➢ MG has extensive experience in structural monitoring and provides a complete service for any monitoring application – on a large or small scale

Project co-funded by the EU under H2020

ACOUSTIC EMISSION (AE) FOR STRUCTURAL HEALTH MONITORING

Jon WatsonInfrastructure DirectorMistras UK

Dr. Athanasios AnastasopoulosVice PresidentMistras Group Hellas A.B.E.E.


http://www.mistrasgroup.com/

Documents

ACOUSTIC EMISSION (AE) FOR STRUCTURAL HEALTH …