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Noncontact Displacement Monitoring by Lasers

Noncontact Displacement Monitoring by Lasers. Upul Attanayake, Ph.D., P.E. Assistant Professor. CAIT Workshop on International Bridge Study (IBS) June 14 – 15, 2011. Laser tracker specifications Laser tracker - accessories Reflector mounting process

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Noncontact Displacement Monitoring by Lasers

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  1. Noncontact Displacement Monitoring by Lasers Upul Attanayake, Ph.D., P.E. Assistant Professor CAIT Workshop on International Bridge Study (IBS) June 14 – 15, 2011

  2. Laser tracker specifications • Laser tracker - accessories • Reflector mounting process • Field implementation - bridge deflection measurements • Summary/Conclusions Outline

  3. Ambient Conditions • Working temperature 0°C to 40°C (32°F to 104°F) • Storage temperature -10°C to 60°C (14°F to 140°F) • Relative humidity 10% to 90%, non-condensing Laser Tracker Specifications • Absolute Interferometer (AIFM) • Wavelength 633 nm / 795 nm (visible / IR - HeNe) • Warm-up time, cold start 8 min • Warm-up time, warm start 5 min • Largest beam diameter 4 mm • Interferometer distance resolution 0.32 μm (0.000013”) • Interferometer distance accuracy ± 0.5 μm/m (± 0.000006”/ft) • Typical lock-on working range 1.0 – 80.0 m (3.3 – 262 ft) • Measuring and Tracking Performance • Measuring rate 3 kHz • Measuring rate output 1 kHZ • Tracking speed lateral > 4 m/s (13 ft/s) • Tracking speed radial > 6 m/s (19 ft/s)

  4. Laser Tracker - Accessories 0.5" Reflector acceptance angle 500 1.5" Red-Ring Reflector acceptance angle of 300 AT MeteoStation (Temp., humidity, and pressure) Laser Tracker Power Supply Control Unit and Laptop

  5. Reflector Mounting Process A reflector with a magnetic base Mounting a reflector using hot glue Access A reflector is mounted next to a potentiometer Mounting a reflector on a girder

  6. Field Implementation -Bridge Deflection Measurements General view of the bridge Plan view of the bridge Reflector location on southbound span 2

  7. Field Implementation - Bridge Deflection Measurements Oct. 10-11, 2010 Girder 3 deflection under 6 LT-BB @ L2

  8. Bridge vibration under transient loads Field Implementation - Bridge Deflection Measurements Maximum deflection at the reflector = 217.09 -216.91= 0.18 in. OR 4.6 mm

  9. Summary/Conclusions Operational Conclusions • Laser Tracker measures deflections and translations without contact. • The technology can acquire static displacements at multiple locations and/or dynamic displacement at a single location at a maximum rate of 3kHz. • Technology can be used during daylight or night (night time is preferred to minimize the interference of sunlight). • Entire operation can be completed in less than two hours on a typical single span bridge including reflector mounting. • A single operator can execute the entire measurement operation if traffic control is provided.

  10. Summary/Conclusions Measurement Related Conclusions • Highly accurate measurements • Resolution of 0.0001” can be achieved very easily under field conditions • Beam divergence requires using 1.5” RR reflectors beyond 160 ft (50 m) under normal operating conditions • 1.5” RRR could read well beyond 260 ft (80 m) distance stated in specifications • Intensity of ambient light can interfere with initial auto measurement settings

  11. Thanks You ! ?

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