The recent collision of a container ship with the Francis Scott Key Bridge in Baltimore has highlighted potential vulnerabilities among some of America’s over 600,000 bridges. The Key Bridge, which had stood for 47 years, collapsed in less than a minute when the Dali, a ship weighing over 100,000 tons, struck it. While such a catastrophic event may not have been entirely predictable, collisions leading to bridge collapses are not unheard of, suggesting that this incident may have been avoidable.
Despite recent federal safety inspections finding the Key Bridge to be in “fair” condition and Maryland’s governor stating that the bridge was “fully up to code,” thousands of bridges across the United States are in poor shape. Around 46,000 bridges in the country have aging structures and are classified as “poor” condition, with 17,000 at risk of collapse from a single impact. Extreme weather events, heavier trucks, and collisions from larger container ships pose significant risks to US bridges, according to engineers and infrastructure experts.
The American Society of Civil Engineers reports that approximately 7.5% of all bridges in the United States, totaling 46,100 bridges, are structurally deficient and in poor condition. While structurally deficient bridges are not necessarily unsafe, they require significant investment for maintenance and are at higher risk for closures or weight restrictions. The number of structurally deficient bridges has decreased in recent years, but the rate of spending on improvements has slowed, with an estimated $125 billion backlog for bridge repairs nationwide.
The $1.2 trillion federal infrastructure law passed in 2021 includes $110 billion for roads, bridges, and major infrastructure projects, which could help fund some bridge improvements. Additionally, older bridges in the country are at risk from extreme weather events and heavier trucks, which can overstress bridge elements and decrease lifespans. Earthquakes are also a significant threat to bridges, and while seismic resilience has improved over the years, not all structures have been retrofitted to withstand intense earthquakes.
Concerns also arise from “fracture critical” bridges, which are vulnerable to collapse from a single hit in the right spot. The Key Bridge was designated as “fracture critical,” highlighting the urgent need to protect older bridges against larger modern vessels. To minimize the risk of ships causing bridge collapses, redundancies like dolphins or fenders can be added to protect vulnerable points on bridges from impacts. These counter-protections are considered a faster and more cost-effective solution than building entirely new bridges.
Recent global incidents of bridges collapsing due to ship collisions underscore the importance of ensuring that bridges are equipped with protections against potential impacts from larger vessels. Building redundancies around bridges’ danger points, such as dolphins or fenders, can help deflect some force in the event of a collision. Ananth Prasad, president of the Florida Transportation Builders’ Association, emphasized the need to reevaluate protection systems around bridge columns in light of larger ships to prevent future bridge collapses.