Have there been any studies about how to prevent ice from forming on suspension bridges, or how to knock it off once it has formed?
A comprehensive review of the subject appeared in the January 2022 issue of Science Direct, “A review of ice and snow risk mitigation and control measures for bridge cables.” The review concluded:
“Due to the rising incidence of icing events on bridges all around the world, a growing number of ice and snow mitigation technologies for bridge cables were proposed and tested in the past two decades. The known systems have been reviewed and divided into two categories and six subcategories based on their application.
It was shown that the most basic methods based on manual removal of snow and ice are highly unreliable, labour-intensive and even dangerous for the workers undertaking the task. These methods are mostly used when bridge operators and authorities encounter the problem of icing for the first time without any experience, and different methods are usually sought afterwards if the risk persists.
The efficiency and safety of operation can be greatly improved by employing mechanical systems, which might be either automated or operated remotely. A few systems tested in the past showed promising de-icing results, but extreme weather events, costly installation or possible adverse aerodynamic effects put stop to their full-scale implementation. Chain-link collars are the only mechanical system currently used in the industry on the Port Mann and Alex Fraser bridges in Canada. Despite some of its drawbacks and potentially high operation costs, the system has been operating for several years now and it is closely monitored. On top of that, two novel solutions utilising the movement of the cable sheathing either by internally-induced vibrations or by means of a motorised unit have been recently proposed and await laboratory and field testing.
Even though thermal systems were considered as a potential anti-icing or de-icing technology in several investigations, none of the systems was economically acceptable due to their considerable power consumption or installation costs. The best candidate, the Pulse Electro-Thermal De-icing (PETD) system, was installed for a trial run on the Uddevalla Bridge in Sweden. It performed reliably and demonstrated very low energy requirements, however, it was decided that the installation cost was not cost-effective and additional aerodynamic evaluation would be required. Nonetheless, the research in this field is still ongoing as many new cable heating techniques have been proposed in recent years.
In the case of maintenance-free passive systems, several innovative methods based on cable surface modifications designed to improve ice and snow retention showed promising results in preliminary wind tunnel tests. More detailed investigation both in the wind tunnel and outdoors is therefore expected to further evaluate their viability for field application.
The review of various chemicals and coatings tested for bridge cable application revealed that none of them can effectively prevent or remove ice or snow accretions. Furthermore, low durability resulting in additional costs for repeated application and environmental impact are of concern as well. Nevertheless, the development in this field is ongoing and a suitable solution may be eventually found.
The last category looked at available ice detection and monitoring methods that should facilitate traffic management in the case of icing events. Many bridge operators around the world already have such systems in place to prevent damage and injuries by timely bridge closures. These systems are currently the safest option to deal with the problem of ice and snow accretion on bridges and should be used in conjunction with suitable ice and snow mitigation methods for bridge cables in the future.”
