BEAR Scotland is carrying out ice mitigation trials on the Queensferry Crossing.
The road bridge had to close to traffic in adverse weather three times since it opened in 2017, due to a risk of ice falling from the cables and towers.
Before the previous winter season, new ice sensors were installed as ‘part of a number of measures to improve the detection and management of ice accretion’, however a closure was still needed in December 2020.
A team of engineers led by Transport Scotland’s operating company BEAR Scotland has been working on the issue and identified soiling of the cables as a potential catalyst for the formation of ice. It is now taking forward trials to test this theory.
Cables on the north tower of the Queensferry Crossing are to be cleaned to measure the impact of soiling on the formation of ice.
Teams of rope access technicians will abseil from the top of the 207-metre concrete tower and use soap and water to wash down the high-density polyethylene sheaths that encase the steel strands of the cables.
Launching on Monday 30 August, the work will take five to six weeks to complete. Ninety-six cables ranging in length from 94 to 420 metres will be cleaned – over 24 kilometres in total, Bear Scotland said.
A 40mph speed limit will be in force on the bridge when rope access teams are working overhead, from Monday to Friday between approximately 07:00 and 18:00.
Chris Tracey, BEAR Scotland’s unit bridges manager for South East Scotland, said: 'Since the Queensferry Crossing opened to traffic, dust and dirt has accumulated on the cables. These tiny particles may be helping ice to accrete as crystals form around them.
'The first cables were installed in 2015 and there are no records of any ice forming on them until 2019. By cleaning the cables on one tower we will be able to measure the impact this has. As part of the project, thermal cameras are being installed at the top of each tower to monitor and measure any formation of ice.
'On this occasion the cleaning will be carried out by rope access technicians, however work is also progressing on the design of a machine to carry out this task in future, should the trial prove successful.'
In parallel to the trial taking place on the bridge, tests are also scheduled in October at the Jules Verne climatic wind tunnel, a research facility at the Scientific and Technical Centre for Building (CSTB) in Nantes, France.
The research facility can replicate different weather conditions, allowing the BEAR Scotland team to test the impact of cleaning and of specialised coatings and deicing compounds on a full-size section of Queensferry Crossing cable.
