Bridge in Bonn: Cracks Monitored Until the Replacement Build

Challenge

Bridging the time until the replacement build safely

After a flood, cracks that threatened the structural integrity were found on a bridge structure in Bonn. A full replacement of the structure was planned, but long-term: it was not due to be completed until 2026. For those responsible, the question was therefore not rehabilitation but how to keep the structure safe in the meantime.

A fast and effective solution was needed to limit the risk from progressing crack formation and to maintain road safety.

Solution

A temporary system for two cracks

A solar-powered gateway with two cabled displacement transducers was installed, one per crack. The cable run to the gateway is 5 metres, up to 25 metres would be possible if more flexibility in the layout had been needed.

Measurements are taken hourly, the values go via NB-IoT to the cloud-based platform. Alongside the crack widths, the gateway’s charge level is tracked: if it falls below 10 percent, an alert goes out. For a temporary installation without a mains connection, that is the difference between a measurement series and a gap in the measurement series.

Result

The alert that came in 2024

In 2024, increased loading of the structure caused the thresholds for crack widths to be exceeded. The alert went out, and the responsible highway authority was able to respond without delay. Within a few days, measures had been taken to reduce the load on the bridge.

That they worked could be read from the same measurement series: the loading declined, the crack widths stabilised, and there was no further exceedance of the critical thresholds. Costly emergency measures were not required as a result.

The project shows what crack monitoring in bridge monitoring delivers when a replacement build is still years away. If you have a structure that needs to hold out until a measure is taken, describe your project to us through our project inquiry.