Imagine driving across a long, suspended bridge when, suddenly, chunks of ice start falling from towering cables above. For engineers, preventing this dangerous scenario has become even harder in our changing climate.
Climate change is resulting in more frequent and intense weather events that have an impact on bridge reliability. This has created new challenges for bridge builders, operators and travellers, who expect bridges to remain open at all times.
After a decade of research, scientists from the National Research Council of Canada's (NRC) Aerospace Research Centre have developed new approaches to testing stay cables under diverse conditions to understand, among other things, the impact of ice buildup or accretion on aerodynamic behaviour. Their research findings are informing recommendations for updates to bridge stay cable requirements developed by the Post-Tensioning Institute.
The specific requirements being updated through this project are published in the institute's DC45.1-18: Recommendations for Stay Cable Design, Testing, and Installation (PDF); guide used by bridge design experts across North America and Europe.
"Climate change is affecting the form of precipitation. Freezing rain and wet snowstorms are becoming more frequent," says Annick D'Auteuil, project manager and research officer at the Aerospace Research Centre's Aerodynamics Laboratory. "To help us better understand how ice accretion affects stay cable aerodynamics, we've performed experimental testing in our 9-m Wind Tunnel—the largest facility of its kind in the world."
Bridging the research gap
Testing these full-scale stay diameter cable models takes a tunnel that can accommodate large models. For the tests, researchers mounted cable models on a dynamic spring system that allows the cables to move freely in wind created by the tunnel's powerful fans. They can adjust the parameters that affect a cable's aerodynamics to better understand how these factors influence cable performance. In fall 2025, the project team completed innovative testing to gauge cable motion, aerodynamic forces and pressure, for 2 cable models with simulated ice accretion representing the extreme conditions for freezing rain, another relevant environmental factor for regulators developing bridge guidelines for a changing climate.
"With this facility, we can do full-scale testing under dynamic conditions," says D'Auteuil, pointing out that the NRC is a leader in doing experimental trials at full scale with simulated ice accretion. "We can also measure levels of damping required to mitigate the vibrations occurring under specific conditions." This information will help bridge designers limit the effect of vibrations on the lifespan of the bridge.
"The NRC's research expertise and world-leading facilities provide an exceptional testing ground for our work in stay cable support for the industry," says Guy Larose, senior technical director at RWDI, a Canadian company performing wind engineering studies for Canadian and international bridge projects. The work the NRC does helps RWDI better support their projects with the industry by increasing knowledge into the aerodynamics of stay cables. "This is an important contribution to building a safer and more resilient bridge infrastructure for Canada."
Keeping the goods moving
Every day, each of Canada's largest long-span bridges carries more than 100,000 vehicles transporting goods and people across them. These bridges include major connections such as Vancouver's 10-lane Port Mann Bridge, Montréal's Samuel de Champlain Bridge and the soon-to-open Gordie Howe International Bridge in Windsor.
Keeping bridges open and safe for traffic is essential to the economy. The recommendations put forward by the project team will help improve the effectiveness of planning and decision-making at the bridge design stage.
This will in turn help reduce service disruptions and related economic losses due to bridge closure, for example.
"The long-term goal is to increase the lifespan and sustainability of these long-span bridges that are critical trade corridors in Canada," says Marianne Armstrong, Director of the NRC's Climate Resilient Built Environment Initiative.
Bridges and other structures have traditionally been designed and built under the premise that climate and weather patterns are cyclical. This is no longer the reality we face in a context of climate change, which alters a bridge's operating environment, affects their life expectancy and increases maintenance needs. To meet performance expectations in the face of rising global temperatures and shifting weather patterns, resilience has become more important.
"Climate change is an ongoing challenge that requires infrastructure to be designed and built differently," Armstrong adds. "And we will continue to work at the interface of research and regulation to help inform the codes and standards that underpin the way we do things."
Armstrong points out that the knowledge and guidance developed by the NRC can be applied anywhere in the world where bridges are affected by ice accretion or wet snow. The NRC's numerous publications on climate resilient bridges are available on the NRC Publications Archive.
As climate patterns continue to evolve in unpredictable ways, the NRC will remain at the forefront of developing innovative solutions that anticipate and address emerging infrastructure challenges. By combining unique research facilities, deep technical expertise, and close collaboration with industry and regulatory bodies, the NRC is helping shape the future of bridge design—ensuring that critical transportation links remain safe, resilient, and reliable for generations to come.
This project is part of the NRC's Climate Resilient Built Environment Initiative, which is led by its Construction Research Centre and funded by Housing, Infrastructure and Communities Canada.
