The Network Rail structures team were concerned about the overall movement of a very old viaduct and were most particularly concerned about the potential propagation of a crack on the underside of one of its main arches. Weekly visual inspections were both expensive and not able to provide sufficiently accurate data on movement over time. Setting up wired sensor solutions were regarded as too expensive and difficult to install given the demands of the location.
Senceive deployed a range of sensors across the bridge. These included a) crack potentiometers along the length of the crack b) a draw wire to assess movement across the full width of the arch and c) integrated tilt meters to assess movement on the sides of the spandrel wall. Temperature was also measured, which is standard in all nodes. Deployment was challenging due to the height of the arch, and the very limited accessibility from beneath. Full track possession was required, and limited to engineering hours at night. Specialist abseiling contractors were used to belay off the rails and access the underside of the arch. Standard FlatMesh sensors were supplemented by several repeater nodes to ensure data was relayed to the solar powered GPRS gateway which was situated a little way from the end of the bridge on top of the approach embankment. Data was monitored and viewed remotely using the Senceive Webmonitor software.
The availability of web based data every 15 minutes provided a key level of critical information which informed the decision to carry out timely remedial work to repair the area in and around the crack. Selected nodes were left in place to ensure continued monitoring following the repair work. In all this was a very successful 18 month installation.