One in every 13 bridges in the US is deteriorating

Tens of thousands of 'aging' bridges

The Francis Scott Key Bridge has been in existence for 47 years, and in that time, it has never suffered a shock so great that anyone would have expected the bridge to collapse.

But when the Dali, a container ship weighing more than 100,000 tons, crashed into Francis Scott Key, the bridge collapsed in less than a minute.

The Francis Scott Key Bridge collapsed completely after just one hit by a container ship on March 26. Photo: CNN

While such a catastrophic collapse may not have been entirely predictable, collision-induced bridge collapses are not unprecedented and could have been avoided.

Recent federal safety inspections of the Francis Scott Key Bridge found it to be in 'stable' condition and Maryland's Governor said the bridge's maintenance is 'fully compliant'. But thousands of other bridges in the US are in poor condition.

According to the American Society of Civil Engineers (ASCE), in the US, 46,000 bridges have old structures and are in 'degraded' condition, and 17,000 bridges are at risk of collapsing after just one impact.

Engineers and other infrastructure experts say extreme weather events, increasingly heavy trucks and collisions from larger container ships pose significant risks to U.S. bridges.

According to the American Society of Civil Engineers' (ASCE) most recent infrastructure report released in 2021, approximately 46,100 of the 617,000 bridges across the United States, or 7.5%, are considered lacking structure and in poor condition.

Factors that threaten bridges

Many of America's older bridges are vulnerable to severe weather events, such as earthquakes or hurricanes. According to ASCE's 2021 report, nearly 21,000 bridges were found to be at risk of foundation threats during severe weather events.

A 2016 report by the US Congress found that the seismic resilience of US highway systems has improved in recent decades thanks to investment in new infrastructure.

However, not every highway has been retrofitted, and there is still no way to build infrastructure that is both cost-effective and can withstand the most intense earthquakes, the report said. know.

In addition, the bridges are adversely affected by heavier trucks than when the bridges were designed. These heavier trucks, which can exceed 40 tons, risk overloading bridge components, causing metal fatigue and cracking, while also reducing the life of the bridge, the ASCE report said. .

Aging infrastructure, inclement weather and larger traffic aren't the only concerns. More than 17,000 bridges are at risk of collapsing after just one impact, known as bridges at risk of 'severe failure'.

That means that if impacted with enough force in the right place, a large section or the entire bridge could collapse, as in the case of the Francis Scott Key bridge.

What protection solution is possible?

Experts say there is an urgent need to improve or protect old bridges against increasingly larger modern ships. The Dali, which crashed into the Francis Scott Key Bridge on Tuesday, was 300 meters long - nearly twice the length of the ships used when the bridge was built in the 1970s.

Fenders are built to protect the bridge piers. Photo: CCG

According to a 2018 report by the International Association of Water Transport Infrastructure (PIANC), between 1960 and 2015, up to 35 major bridges across the planet collapsed due to collisions with ships or barges. , leaving 342 people dead.

In the first three months of this year, in addition to the Francis Scott Key Bridge collapsing in Baltimore, a bridge in southern China was cut in half and part of a bridge in Argentina was also broken after large commercial ships collided with they.

'Ships are getting bigger and container ports are focusing on increasing cargo transport.' Ananth Prasad, president of the Florida Transportation Builders Association, told CNN. 'But as well as encouraging larger container ships, we also need to protect bridges in these one-off situations.'

According to Mr. Prasad, to minimize the possibility of a ship crashing into the bridge, it is necessary to build with backup safety plans and protection around dangerous points of the bridge.

These can be rows of wooden or steel piles driven into the seabed or riverbed and connected above the water to form a hard fence protecting the bridge; or 'fenders'. The structures surrounding bridge piers are designed to deflect some of the impact forces.

Adding these protections would be faster and more cost-effective than building a new bridge, Mr. Prasad said, and even more so given the tens of thousands of bridges that are falling down. level, or in unsafe conditions in the United States.