First UK bridge restored in golden eight hours

Apr 24 2009 by Chris Knox, The Journal

Paul Musgrave, regional director of Faber Maunsell, said: “The presence of the 25kV overhead lines prevented a more conventional approach of constructing a new deck to the side of the existing bridge, and craning it into position.

“There was insufficient time to dismantle and re-erect the overheads within the eight hours available, which would have allowed the use of cranes at track level, so we had to look at a design where we built the supporting structure from underneath.

“Once the supporting structure was complete, the overhead lines were isolated to ensure the safety of the construction personnel carrying out the final ballasted track installation.”

The structure is now only the third eight-hour bridge replacement to have been carried out in the UK, and the first to have been undertaken under overhead electrification.

The design comprised of a reinforced concrete portal structure, on piled foundations, constructed between the existing stone abutments. The reinforcements were built underneath and around the existing wrought iron girders, enabling the bridge to remain open to traffic during the construction works.

“We had to make sure that the temporary works maintained the stability of the existing abutments and waybeams during construction of the new works to maintain tolerances and keep the trains running at all times,” Musgrave said.