During a 2017 inspection of the existing gantry rails on the Forth Road Bridge, it was decided that they needed to be replaced after defects were discovered.
Millar Callaghan were awarded contracts for both the trial works, to replace a 20-meter section of rail and also the main works, to replace the remaining 3220 meters. To allow the new rails to withstand the extreme conditions and loading that they would be exposed to on one of the country’s most iconic structures, a special rolling was commissioned at British Steels Redcar works to produce a unique beam, specifically for this contract. Over 2 miles of rails were produced weighing in excess of 400 tonne.
Millar Callaghan’s rope-access trained personnel carried out a full survey of the existing bridge structure to ensure that each newly fabricated beam, which was custom made for each unique location on the bridge, was a precise fit.
To access the rails during the installation of the new beams, Millar Callaghan designed and fabricated a series of working cradles that would be suspended from both the existing and new rails. This would allow the rails to be replaced between the two gantries as they progressed down the length of the bridge.
Fabrication of the new gantry rails was carried out at our Irvine workshop, before they were blasted and galvanised to 140 microns.
A 4-tonne spider crane was positioned onto the bridge cycle-path to assist with the removal of the redundant beams and installation of the new beams. The installation process started at one end of the bridge and moved forward one beam at a time, until it was completed at the opposite end. The installation of over 2 miles of gantry rails was successfully completed within programme and on budget.
