Checking the decks: Real time road monitoring in Southampton

Warrington based Testconsult designed and installed an array of equipment capable of recording loads and movement in reinforced concrete bridge decks as part of a £2.4M bridge bearings replacement project.

Pot bearings on the A34 Redbridge Flyover built in the 1970s had fallen into disrepair.

Now specialist main contractor Concrete Repairs is part way through a programme to refurbish the flyover. During the work it is being supported by a modular steel lattice and hydraulic jacks designed by Mabey Support Systems.

A sensitive touch

Instrumentation specialist Testconsult installed a series of pressure, tilt and temperature sensors designed to monitor the bridge deck as it is jacked free of the pot bearings. Monitors measure the displacement between the deck soffit and top of pier as well as the deck’s displacement and pier foundations enabling engineers to plot any rotational movement.

“The deck is very weak in torsion so a range of tilt sensors have been installed. These are incredibly accurate - they can measure up to 200ths of a degree - and we are able to provide real time data to the jacking supervisor so that he can control the pressure on individual jacks,” says Testconsult instrumentation engineer Tim Neats.

Data gathering

Master loggers on each pier collate information from the sensors as the deck is jacked clear of its bearings. As the jacks are locked off, the monitoring system provides logging data with predetermined emergency levels programmed in. If any of these levels are exceeded the system instantly alerts engineers.

The monitoring system also ensures that engineers meet the tight lateral displacement tolerances of +/- 0.2mm.
“Basically once the bearing has been repaired and the bridge is dropped back to its final resting point it has to be in the same position,” says Neats. “That can be difficult but we have installed the monitoring equipment to allow that to happen.”

The nine month project is due for completion in early spring.

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