Advanced video data paves way to smarter bridge monitoring

Urgent task of modernising ageing infrastructure

Along with tunnels, viaducts and aqueducts, the Moerdijk Bridge is one of many structures that keep the Netherlands’ economy moving and communities connected across a complex geography of land and water.

However, these vital assets are ageing and face the growing impacts of heavy traffic and climate change. They require future-proof strategies for monitoring deterioration and planning interventions that minimise disruption, reduce carbon footprint, and deliver best value from maintenance budgets.  

Looking for a solution, Rijkwaterstaat focused on accelerating digital innovation to support smarter, data-driven asset management, maintenance and replacement. As part of this, Fugro and our partner Witteveen+Bos were asked to evaluate camera technologies in the Moerdijk Bridge pilot study and how they might add value to infrastructure assessment.

Solution to updating tradition

The Moerdijk Bridge carries the A16 motorway over the Hollandsch Diep river, connecting the island of Dordrecht in South Holland with the industrialised municipality of Moerdijk in North Brabant. The current 1,018 m steel structure was constructed in 1978 and is among the country’s largest and strategically most important bridges.

In total, Rijkswaterstaat manages 1,145 bridges including 168 dynamic designs, many of them built between the 1950s and 1970s.

These bridges are normally visually inspected to assess their condition. In stepping up to smarter decision-making, Rijkswaterstaat sought more efficient ways to inspect them leveraging time-saving remote and digital technologies.

Cameras as multifunctional sensors

The use of smart sensors, for example based on optical fibers, has been growing as we rely on smarter calculations to better determine the condition and safety of vital structures.

But placing sensors directly on a bridge is not always ideal. Their installation may require traffic closures, incurring costs and causing disruption for businesses and the public. Additionally, sensors only provide information for a limited area. Measurement data for larger expanses is vital to improving assessment accuracy and making robust, holistic predictions of lifespan.

Here, visual technologies using cameras offer significant added value by providing information about the entire image surface. It is also possible to observe several parameters at once with a camera, such as traffic and vibrations.

Getting more from movement data

Dynamic loads on a bridge – such as traffic and wind – cause movement of the structure and are important parameters for calculating strength. Changes in motion behaviour may also indicate damage or extreme strain. These movements cannot be registered with the naked eye but can be detected with smart image processing techniques.

During the four-day study, we evaluated the scope of two technologies for recording these movements:

• Motion magnification: amplifies movements in a video, giving greater visibility of how a construction moves. This information is extremely important for validating dynamic behaviour based on simulations from data models.

• Virtual sensors: can quantify movements down to sub-millimetre level for specific points with high contrast. Our experts analysed and compared these results with, among other things, fixed sensors on the bridge.

Movement study findings 

We found that the measured movements using the two technologies correlated well, underpinning confidence that they can be successfully applied in tandem. They offer a suitable method for recording the global behaviour of the bridge and, for example, determining the first natural frequency and modal shape.

In addition, we were able to make informed judgements on the best practice use (and limitations) of combining the technologies.

Going deeper with thermal cameras

We also looked at the use of thermal cameras for taking temperature measurements, recording the thermal behaviour of the entire bridge structure continuously for the full study period.

The results showed that an absolute temperature measurement is useful. Advancing on this, we found that temperature curves provide especially important insights. A big temperature difference could be the result of leakages and may be an indicator of crack formation. We also observed some large temperature differences which could potentially cause high local stresses in the steel – another indicator for further investigation.

Extracting value through data integration

Our Geo-data analysts processed huge volumes of data, based on 100 measurements per second for multiple points, along with bridge dynamic characteristics (natural frequencies). We overlaid the resulting thermal and dynamic data with results from traditional technologies, in other words accelerometers and in situ temperature sensors. This allowed us to compare data quality and determine what insights we had gained into bridge conditions.

We concluded that the imaging technology provides a better spatial resolution, empowering engineers to assess spatial differences and more effectively assess an entire structure on structural integrity and residual service life.

Moerdijk Bridge study outcomes

Measuring with cameras is a useful addition to existing technologies for gathering information about civil engineering assets.

The motion and thermal technologies evaluated were found to offer the following advantages and potential:

• Harnessing visual data from a larger area provides vital insight to supplement data from specific points. Whereas localised sensors can provide detailed information at critical points, the visual data gives insight on the behaviour of the bridge as a whole;

• By increasing spatial imaging and cross-matching data, we can build a more complete, accurate picture of structural health as well as anomalies and red flags needing closer scrutiny; 

• Digital streaming from remotely installed, multifunctional cameras allows monitoring to be easily implemented and scaled to different structures with minimal disruption to ongoing traffic;

• Multiple data streams tracking different facets of structural behaviour will support dynamic digital twins, including faster, more accurate calculations of the structural safety and residual lifetime of a bridge. This in turn allows for more effective decision-making regarding bridge operations and maintenance.

Inspiring innovation

The bridge study findings are feeding into wider collaborative work under the Dutch government’s National Growth Fund. Fugro is a member of a consortium of approved specialists participating in the Future-Proof Living Environment programme , focussing on data-driven innovation.

Scalable bridge monitoring

We are exploring the potential to use relatively simple imaging/camera technologies boosted by advanced data analytics to extract new layers of detail for the visual monitoring of ageing infrastructure. The combination of available imaging technology with dynamic post-processing would allow easy, cost-effective replication and scaling to different monitoring challenges.

This could transform the baseline of data for smarter decision-making on the type and timing of repairs and maintenance, asset replacement and the feasibility of extending service life. That’s a big win for managing budgets, forecasting costs, and reducing carbon footprint from unnecessary new construction.