A hole on the Sauvagine Bridge in Chateauguay, Québec, on March 4, 2026. (Eric Allard, Mayor of Chateauguay/Facebook)When a large hole recently opened up in the deck of a bridge in Châteauguay, Québec, many people were understandably alarmed. Some residents even expressed hesitation about using the bridge after seeing images of exposed reinforcing steel and damaged concrete, and some told local media they were reluctant to cross it.For drivers who cross the structure every day, the scene raises a question: how can such a dangerous incident suddenly happen on a bridge that is still open to traffic?In reality, incidents like these rarely occur overnight. What the public sees as a sudden failure is often the visible result of deterioration that has been developing inside the structure for many years. (CTV News) Canadian bridges built decades agoIn most cases, what fails in situations like these is not the entire bridge but the deck — the concrete slab that vehicles drive on. While serious, a localized deck failure is different from the collapse of the bridge’s primary load-bearing structure. Bridges are typically designed with multiple structural components that share loads, and engineers carefully assess these elements before deciding whether traffic can continue safely on part of the structure.Still, the appearance of such damage highlights a broader challenge facing cities across Canada: aging infrastructure.Many bridges currently in service were built decades ago, often in the 1950s, ’60s and ’70s. Over time, Canada’s unforgiving environmental conditions gradually deteriorate reinforced concrete structures. In Québec, the combination of freeze–thaw cycles, water infiltration and the use of de-icing salts during winter creates particularly harsh conditions for bridge decks. Chlorides from road salts can penetrate the concrete and corrode the steel reinforcement inside. As corrosion progresses, the expanding rust causes cracking and separation within the concrete, sometimes leading to pieces of the deck breaking away.Because this process develops internally, deterioration may not always be immediately visible from the surface. By the time cracks or holes appear, the damage could have progressed for years.Identifying problems in advanceFor engineers, one of the main challenges is to understand what damage means for the structural performance of the entire bridge. Visual inspections remain an essential tool to detect damage, but they don’t always reveal how deterioration affects the structural behaviour of the structure.Our research has found that computational modelling may provide important insights about how to interpret the damage. Numerical simulations can mimic mechanisms like cracking, material degradation and changes in the interaction between steel reinforcement and concrete. By incorporating these effects into structural analyses, engineers can better estimate how much capacity an aging structure may still retain and identify potential vulnerabilities before they lead to more serious problems. Read more: Aging bridges are crumbling. Here’s how new technologies can help detect danger earlier In addition to the visual inspections and monitoring data, computational modelling can also offer a cost-effective way to assess aging infrastructure. By using simulations, virtually created scenarios allow engineers to investigate how deterioration mechanisms — such as cracking, corrosion or degradation of the bond between reinforcement and concrete —influence the structural behaviour of a bridge. These simulations can help evaluate how local damage, like deterioration in a bridge deck, may influence how the structure of the bridge could respond. Because these analyses rely primarily on computational tools rather than large-scale physical interventions, they can provide valuable insights at relatively low cost and help guide more informed decisions on maintenance and retrofitting.Long-term safetyThe incident in Châteauguay is yet another reminder that Canada’s infrastructure is rapidly aging. To ensure public safety, policymakers must be proactive instead of reactive. To ensure safety, better tools must be developed to understand the hidden processes that gradually weaken structures over time. These tools will result in faster and more informed interventions for modern repair and for retrofitting.As bridges across the country continue to age, ensuring their long-term safety will require a combination of regular inspection, timely maintenance, advanced engineering analysis and the application of effective strengthening techniques when needed. Troubles may begin with big holes in bridge decks, but they ultimately point to the need for much larger conversations about how governments maintain and renew the infrastructure that millions of people rely on every day.The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.