Bridges work continuously under traffic, wind, temperature and earthquakes. Periodic visual inspections catch surface problems, but changes in a structure's stiffness and dynamic behaviour only show up in measurements. A structural health monitoring system tracks these changes continuously and provides data for maintenance, strengthening and reopening decisions.
What we measure
- Acceleration and vibration: modal frequencies, mode shapes and damping ratios,
- Strain: stress changes in critical members,
- Displacement: contactless measurement with image processing where needed,
- and from these, condition assessment and fatigue life estimation.
Field examples
Bosphorus Bridge hanger replacement
When the 1973 Bosphorus Bridge had its inclined hangers replaced with vertical ones in 2015, our team measured the bridge's vibrations at every stage. Deck-dominated modal frequencies dropped by 6–16% while tower modes stayed nearly unchanged; the findings were confirmed by finite element models of both configurations (Structure and Infrastructure Engineering, 2020).
Historical stone arch bridges
On a railway line crossing the North Anatolian Fault with 41 registered historical bridges, the modal properties of 12 stone arch bridges were identified from ambient, impact and train-passage vibrations. Finite element models were updated to match the measurements, giving a reliable basis for the seismic assessment of heritage bridges (Journal of Earthquake Engineering, 2019).
Long-term monitoring
On a 111 m concrete bridge monitored for five years with 13 wireless accelerometers, stiffness, mass and soil-spring values were identified year by year from 1,707 traffic-induced vibration datasets: about a 5% decrease in the first modal frequency and 2% in superstructure stiffness over five years (Computer-Aided Civil and Infrastructure Engineering, 2009).
These small measured changes reveal what is happening in the structure before it becomes visible. Monitoring data helps spend maintenance budgets on the right bridge at the right time and, after an earthquake, decide quickly whether a bridge can stay open to traffic.
Which bridges is it for?
What Motusmec does
For bridge owners, operators and contractors we provide sensor layout design, installation, continuous monitoring with our in-house software, comparative measurements before and after interventions such as strengthening or hanger replacement, and post-earthquake condition assessment.
Frequently asked questions
Does bridge monitoring require closing the bridge?
Continuous monitoring systems work under normal traffic; measurements are taken during everyday use. Installation may require short lane arrangements depending on sensor locations.
Can an old existing bridge be monitored?
Yes. On older bridges, measurements reveal the bridge's actual behaviour even where documentation is missing, and allow the numerical model to be updated to match.
Can the effect of strengthening or repair be measured?
Yes. Measurements before and after the intervention show the change in modal properties; our work during the Bosphorus Bridge hanger replacement is an example.