The Redbridge and Millbrook flyovers needed structural improvement and bearing replacements. This busy road in Southampton supports the A33 dual carriageway which runs from Reading to Southampton. It was important to keep traffic disruption to a minimum throughout the project. The road mostly remained opened apart from some night closures whilst the jacking was in progress.
The Redbridge and Millbrook flyovers are used every day. We had to find a solution to monitor the different sections of the pier and bridge deck while structural improvements were made to the bridge. To add to the complexity, our solution had to be adaptable for each pier.
We built a bespoke 24-hour structural monitoring system, which we could install quickly and have the ability to relocate the monitoring system and sensors from pier to pier. The bridge deck required precise control monitoring within sub millimetre tolerances.
The bridges were propped and lifted in a controlled manner, with precise computer controlled 24-hour monitoring. The jacks were locked off on mechanical collars whilst the existing bearings were removed using hydro-demolition.
In order to do this, displacement, pressure and tilt sensors were installed and linked to IMS software to record and report any excessive movement via text message alerts. The system consisted of bespoke manifolds and robust plug and play sensors, allowing a quick installation and the ability to relocate the monitoring system and sensors from pier to pier, as and when the bearings were replaced.
The project specification required the monitoring of the bridge deck relative to the top of the pier along with the absolute displacement. The movement between the underside of the jacks and the top of the pier base was also being measured.
The angle of the bridge deck was also measured and controlled using tilt sensors for accurate measurement of the deck angle. The accuracy of the system was ±0.2mm. The data from the master log, located at the pier, receives the data from the various sensors and uploads the data via a secure website where x-y graphs are displayed, this is accessible by username and password security protocols.
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