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Structural Health Monitoring (SHM). Structural integrity assessment for buildings, bridges, offshore oil rigs, aerospace structures etc. Goals of SHM: Detection “is there damage?” Localization “where is the damage?” Quantification “how severe?” Prognosis “future prediction” Why SHM?.

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Structural health monitoring shm
Structural Health Monitoring (SHM)

  • Structural integrity assessment for buildings, bridges, offshore oil rigs, aerospace structures etc.

  • Goals of SHM:

    • Detection “is there damage?”

    • Localization “where is the damage?”

    • Quantification “how severe?”

    • Prognosis “future prediction”

  • Why SHM?


Sensor networks for shm
Sensor Networks for SHM

  • Current SHM

    • Bi-annual visual inspections (most common)

      • Limitations of human accessibility and error

      • Catastrophic failure between inspections

    • Expensive wired data acquisition systems

      • Extremely high installation, cabling, and maintenance cost

  • Wireless Sensor Network based SHM system

    • Flexible, fast and low cost deployments

    • No cabling cost


Vibration based shm
Vibration based SHM

  • Measure and analyze structural vibrations induced due to heavy winds or earthquakes, etc

  • Principles behind structural algorithms can be illustrated by strings

    • Structural response is composed of several harmonics - modes

    • Mode = < Frequency, Mode Shape>

  • Damages alter the structural properties and hence the modes

  • Structural response is measured by using sensors (accelerometers, strain gauges) at several locations in the structure



Requirements for shm applications
Requirements for SHM Applications

  • Reliable Delivery

    • SHM applications are loss-intolerant, sensors need to transmit data reliably

  • Time Synchronization

    • Data from various sensors should be time-synchronized to within 100 micro-sec for damage localization.

  • High Data Rates

    • A hundred tri-axial sensors sampling at 500Hz can generate a data rate of 5Mbps.

  • Dense Sensing

    • The larger the number of sensors the better the performance


Deployment

Sensors

Actuators

Motes

Deployment

  • Building Details

    • 48 inches high, 4 floors, 60 lbs

    • Floors –1/2 x 12 x 18 aluminum plates

    • steel 1/2 x 1/8 inch steel columns

    • 5.5 lb/inch spring braces

    • 4 actuators on the top floor

    • 8 motes, 2/floor

  • 4 Test Cases

    • braces from floor 4 removed

    • braces from floor 3 removed

    • braces from floor 2 removed

    • braces from floor 2 and 4 removed

Jeongyeup Paek, University of Southern California


Damage detection and localization on scaled model
Damage Detection and Localizationon scaled model

Jeongyeup Paek, University of Southern California


New developments in shm systems

Graphics

Info.

Text

Data

Users

Fiber Optic

New Developments in SHM Systems

Remote Command &

Control

and Display

Real-Time

Alerting

Health

Monitoring

High-Speed

Event

Recording

Time

On-Line

Off-Line

Multitasking

Processing

Resolution

Satellite

IP

Telephone

RadioCellular

‘70

‘80

90

Dynamic Range of

Data Logger

Structure

Control CenterGateway

Communications

Kinemetrics Inc.


Wireless bridge instrumentation
Wireless Bridge Instrumentation

Users

Internet

Wireless

Intranet

Control Center

Gateway

Kinemetrics Inc.


Typical sensors used in bridges
Typical Sensors Used in Bridges

  • Accelerometers

  • Strain gauges

  • Wind speed and direction

  • Temperature transducer

  • Displacement transducer

  • Deflection/Tiltmeter

  • High precision differential GPS

  • Others

  • Audio & Video