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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?.

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Structural Health Monitoring (SHM)

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  1. 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?

  2. 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

  3. 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

  4. Existing SHM Techniques

  5. 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

  6. 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

  7. Damage Detection and Localizationon scaled model Jeongyeup Paek, University of Southern California

  8. 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.

  9. Wireless Bridge Instrumentation Users Internet Wireless Intranet Control Center Gateway Kinemetrics Inc.

  10. 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

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