New approaches to railroad bridge monitoring

Over 25,000 railway bridges across Germany fall into the accountability of the bridge monitoring department at DB InfraGO AG. Supported by ASC Sensors’ expertise, the DB bridge experts are working on an innovative pilot to make the monitoring and proactive maintenance of critical railroad bridges simpler, safer and more cost-effective in the long term.

Minimizing or preventing operational disruptions

Bridge measurement is always complex. It requires time, qualified staff, extensive material and often widely laid out cables. "Everything we do has an impact on regular operations," says engineer Peter Krempels, team leader of the measurement unit at DB InfraGO. To address this, a pilot project jointly with ASC is currently evaluating an innovative measurement concept using smart sensor technology, to minimize or prevent operational disruptions both for the railway and the road operator. To that end, smart sensor systems of the ASC AiSys® ECO series are specially tailored to the diverse conditions of a wide range of bridge structures. Apart from the materials used, the type of construction, its length and many other factors play a role. "No sensor model covers all requirements. The flexible configuration of sensor systems is therefore an advantage," states the measuring engineer.

Smart, flexible sensor technology enables continuous monitoring

ASC's innovative MEMS-based accelerometer systems offer a complementary approach to traditional reference-based monitoring methods. By providing accurate, real-time dynamic displacement measurements, they enhance the monitoring toolkit without need for fixed reference points. This feature simplifies installation and increases measurement flexibility.

A key indicator of the condition of a railroad bridge is its displacement. Unlike static displacement, which measures changes in position under constant loads or conditions, dynamic displacement captures how a bridge reacts to variable forces such as traffic, wind, seismic activity, or temperature changes. Installed at defined measuring points, the sensor systems are designed to permanently monitor all relevant parameters and continuously analyze them in a multi-stage process. These include:

• High-frequency data sampling 
• Adaptive real-time DC offset removal
• Advanced filtering and decimation 
• Double integration and drift correction
• Phase correction and artifacts removal 
• Integrated processing and data output

Early alert system for railway engineers

"Instead of waiting for problem reports and reacting individually – on the alert by the local colleague on site who regularly inspects 'his' bridges visually – we want to permanently monitor critical structures and proactively maintain them before acute damage shuts down operations," says Krempels. "We expect this approach to keep many bridges in good condition, operating safely and economically for longer.”

Automated data integration of ASC’s smart sensor systems is crucial for this to work. "Not only should this enable us to have the results available in real time, but also to receive appropriate alerts and actions instantly," states Krempels. This is a major advantage for engineers who, with conventional laser methods, would still have to invest a lot of time in analyzing results, meeting to discuss the gained insights and develop recommendations for action.

Reliable sensors and flexible partnership

"Conditions are different for each individual bridge. That's why our test pilot jointly with ASC is critical in order to learn to correctly assess all influencing factors before we go into broader application," the expert says. One challenge is to keep measurements stable despite a wide range of rapidly changing loads – regardless of train weight, speed, centrifugal forces, climate changes and so on. "This is another reason why we need reliable sensors of maximum precision and long-term stability."

In order to select the right bridges for economical long-term monitoring and then switch over from conventional spontaneous measurements, DB InfraGO has been conducting intense tests with ASC AiSys ECO accelerometers for some time. "These test series have recently been very successful, so that we can now decide on next steps," states Krempels.

“For this innovation in rail bridge monitoring, we were looking for a competent partner who not only had a flexible range of high-quality digital and smart inertial sensor solutions, but was also willing to go down this new path with us," recalls Krempels. For example, other suppliers would not be prepared to adapt their standard sensors specifically for our pilot project, adapt software to individual needs or produce small quantities for our test series. "ASC has been able to respond to all our requests so far, has proven to be a flexible partner and invested a lot of time in understanding our requirements and implementing them jointly, despite the small quantities."

To discuss this and further tailormade railway and rail infrastructure sensor solutions, see us at InnoTrans 2024!