Bridge Modal Analysis Without Sensor Installation
Two field demonstrations show how Q2 delivers 65 simultaneous non contact velocity signals for rapid, repeatable mobile bridge vibration monitoring under live traffic and a train crossing without lane closures or user interference.
For a platform-level view of when to use Q2 versus QMini, Q1S or Q1, see the Q-series comparison reference.
Discuss the application
Application Overview
Usage of Ommatidia's Q2 Laser RADAR provides a fast, safe, repeatable measurement layer between visual inspection and fixed SHM systems.
- Operate from accessible standoff positions.
- Avoid contact with structures with degrading surface properties.
- Acquire enough spatial information during the same operational event to compare locations, extract local strain, and identify weak spots.
Q2 Approach: 65 Simultaneous Non-Contact Measurements
Position Q2 where there is a clear line of sight to the bridge area of interest. The instrument projects a line of laser beams across the structure, with each illuminated point acting as an independent Laser Doppler Vibrometry channel.
Outputs from one acquisition include:
- Time-domain vibration response during traffic or train passages.
- Displacement estimates obtained by integrating velocity signals.
- Frequency spectra and dominant vibration components.
- Point-to-point comparisons across the 65 measurement channels.
- Model-based strain estimates where applicable.
- Field quality checks using the internal accelerometer.
How It Works
Ommatidia Q2 is based on multichannel laser Doppler vibrometry, a non-contact technique that measures vibration by detecting the Doppler shift of laser light reflected from a moving surface.
Instead of installing accelerometers or strain gauges on the bridge, Q2 projects a line of 65 laser beams onto visible structural points from a safe observation position. Each beam acts as an independent vibrometry channel, recording line-of-sight surface velocity at the same instant.
This simultaneous acquisition is what makes the system different from single-point LDV: it captures how different parts of the bridge respond to the same event while keeping setup fast, remote, and repeatable.
Operational Benefits
Proof Points
- Operational events captured: elevated vibration levels during vehicle passages and the train crossing were clearly recorded.
- Spatial variation: different channels showed distinct responses, providing richer context than single-point measurements.
- Frequency-domain insight: recurring low-frequency components appeared across repeated road-bridge acquisitions, while railway spectra changed clearly before, during, and after crossing.
- Quality control: comparison with the internal accelerometer helped separate bridge-driven content from possible setup motion.
Talk to Ommatidia LiDAR
Discuss how this measurement approach could support applications workflows with the Ommatidia LiDAR team.
