Lab tests for measures to stop ice falling from Queensferry Crossing
Te c h n o l o g y t o p r e ve n t i c e falling from the Queensfer - r y Crossing is to be tested in a specially-created laborator y that will replicate the climactic conditions required for ice to form on the bridge.
T h e r e ve l a t i o n f o l l o w s a four-hour closure of the crossi n g o n Fr i d ay a f t e r n e wl y - installed sensors detected ice for the first time and it was seen falling from the towers.
The Scottish Government’s Transp or t S cotland agency said options that may be tested included “cable sheath surface modifications” to retain and control ice, mechanical vibration system, ultrasonic de-icing systems and robotics.
However, it said using heated wires to prevent ice build-up, or “accretion”, would pose “significant maintenance challenges”.
The agency said mock-up laboratory and on-site trials of the other options were being considered.
A s p o ke s p e r s o n t o l d T h e Scotsman: “This will require the use or construction of a facility which can replicate the climatic conditions required for ice to form so that each developing option can be confirmed to actually work in the particular circumstances found on the crossing.”
Ice accretion on the bridge only occurs when temperatures of around 0C are accompanied by particular levels of relative humidity, specific wind speeds and wind direction and the dew point – when air become saturated with water vapour.
Any option found to be viable to tackle this would then be tested for value for money.
It would also b e assessed a g a i n s t u s i n g t h e a d j a c e n t Forth Road Bridge as a diversion route, which is to be tested on Saturday night when both bridges will be closed from 10pm to 8am on Sunday.
The exercise is to see how long it would take to switch traffic if ice forced the closure of the three -year- old Queensferr y Crossing again.
The Forth Road Bridge could not be used on Friday because it was closed for the replacement of expansion joints under its carriageways.
Designers of the Queensferry Crossing had thought ice would be a relatively rare occu rrence, but it happened last year when several vehicle windscreens were smashed, and again in February.
Transport Scotland said its research showed that a perfect solution to tackle the ice threat had not been devised for any other bridges globally.