# Bridge integrity

A study performed by VG in 2017 (De forsømte broene) showed that the Norwegian Public Road Administration do not have the capacity nor economy to follow the rules meant to secure that Norwegian road users can drive safely across bridges. A main reason for this is the cumbersome process of how the bridges are overlooked in terms of various inspections and reporting procedures. The main question in this use-case is therefore:

Is it possible through better use of monitors, more effective analyses and/or better experiments and simulations to maintain the safety of bridge users and still keep the costs at a reasonable level?

One possible solution to this could be to install an automatic surveillance system that’s helps the operator in terms of both deciding when it necessary to perform inspections, but also alert the road users and instantly close the bridge if something unforeseen causes safety issues. I.e. the surveillance system should be able to catch both:

  • Structural degrading over time
  • Instance incidents that causes safety issues

Best data-sources are those which can be provided through monitoring systems and includes, but is not limited to:

  • Accelerometers
  • Stress gauges
  • Temperature sensors
  • PH-probes
  • Image sensors

# Recent bridge incidents

The main issues regarding operation of concrete bridges are in association with corrosion and alkali reactions. These are typically very slow processes (take years to progress), often hidden within the concrete and therefore difficult to monitor. A recent example of a bridge that may have (not concluded upon) collapsed due to corrosion issues is the Genoa Bridge located in Genoa, Italy. Corrosion damage has been reported for the southern stays, which may have caused the instant collapse.

The Morandi Bridge after the collapse that occurred on August 14, 2018. This view is to the east from the Genoa West junction.

The Morandi Bridge after the collapse that occurred on August 14, 2018. This view is to the east from the Genoa West junction. (Michele Ferraris - Own work - CC BY-SA 4.0)

For more details and images see story on archdaily.com.

Similar to concrete bridges, corrosion is also an issue for steel bridges, but here it is often easier to discover through visual inspection. Fatigue is also a big concern with respect to steel bridges, as shown in the Fig. 1 of (Cheng et al. 2017) where typical fatigue cracks are displayed for orthotropic bridge decks.

Another reason that may cause damages to a bridge or in worst case make it collapse is due to foundation failure. This was seen for the Skjeggestadbrua in Vestfold, Norway.

Skjeggestadbrua

Skjeggestadbrua (Tore Meek - NTB scanpix - CC-BY-NC-SA-4.0)

For more details see story on tu.no